High Performance CsPbIBr2 Perovskite Solar Cells - ACS Publications

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High Performance CsPbIBr2 Perovskite Solar Cells: Effectively Promoted Crystal Growth by Anti-Solvent and Organic Ions Strategies Boxue Zhang, Wenbo Bi, Yanjie Wu, Cong Chen, Hao Li, Zonglong Song, Qilin Dai, Lin Xu, and Hongwei Song ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b09171 • Publication Date (Web): 23 Aug 2019 Downloaded from pubs.acs.org on August 23, 2019

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ACS Applied Materials & Interfaces

High Performance CsPbIBr2 Perovskite Solar Cells: Effectively Promoted Crystal Growth by Anti-Solvent and Organic Ions Strategies Boxue Zhang,a,b Wenbo Bi,a Yanjie Wu,a Cong Chen,a Hao Li,a Zonglong Song,a Qilin Dai,c Lin Xu,*a and Hongwei Song* a

a

State Key Laboratory on Integrated Optoelectronics, College of Electronic Science

and Engineering, Jilin University, 2699 Qianjin Street, Changchun, 130012, People’s Republic of China. b

College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, P. R.

China c

Department of Chemistry, Physics, and Atmospheric Sciences, Jackson State

University, Jackson, Mississippi 39217, USA.

E-mail: [email protected], [email protected]

Keywords: Perovskite solar cells, Guanidinium, Passivation, Anti-solvent, Stability.

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Abstract Growing attentions have been received in CsPbIBr2 perovskite solar cells (PSCs) after balancing the band gap and stability features of the interested full-inorganic perovskites. However, its power conversion efficiency (PCE) still lags behind the PSCs using hybrid halide perovskite, and how to increase the corresponding PCE is still a challenge. Herein, anti-solvents and organic ions surface passivation strategies were systematically applied to precisely control the growth of CsPbIBr2 crystals for constructing a high-quality full-inorganic perovskite film. Through careful adjusting, CsPbIBr2 film with pure phase, full coverage, and high crystallinity with preferable (100) orientation was successfully obtained by introducing diethyl ether as the anti-solvent and followed by guanidinium surface passivation. The optimal CsPbIBr2 film was composed by the big grain with an average size of 950 nm, few grain boundaries as well as higher hydrophobic property. Planer PSC using the optimal CsPbIBr2 film and electron beam deposited TiO2 compact layer exhibits a PCE of 9.17% which is ranking in the highest PCE range of the reported CsPbIBr2 PSCs. Besides, the designed CsPbIBr2 PSC exhibited good long-term stability which could maintain 90% of the initial PCE in 40% humidity ambient and kept constant after heat treatment at 100oC for 100 h. Based on the optimal CsPbIBr2 film, the flexible and large area (up to 225 mm2) PSCs were further fabricated. The adopted film improved methods were further extended to other kinds of full-organic PSCs, demonstrated the universality of this strategy.


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1. Introduction Since 2009, the power-conversion efficiency (PCE) of organic-inorganic hybrid perovskite solar cell (PSC) has realized a tremendous improvement, which increased from 3.8% to 24.2% up to now.1-7 It has been considered as a strong candidate for commercialization and outdoor applications due to its high absorption coefficient, high charge carrier mobility, and long electron-hole diffusion length.8-9 However, the long-term stability of organic-inorganic hybrid perovskite is still a main challenge due to the photo, thermal, and humidity instability caused by the intrinsically volatile nature of the organic components. To address this issue, some efforts have been taken, such as cell encapsulation, interface modification, perovskite doping, and full-inorganic perovskite introduction.10-15 Among these methods, replacing the fragile organic group by inorganic cesium (Cs) cations to build a fully inorganic light absorption layer is an effective way. To date, Cs based lead halide perovskites (CsPbX3, X =I, Br, Cl or mixture) has been proved to exhibit similar charge carrier mobility to those hybrid perovskites,16 while the corresponding PSCs using CsPbX3 can maintain 98% of the initial PSC under 80% humidity over 40 days17 and keep the PCE value almost constant after being continuously heated at 100°C for more than 2 weeks.18

Accordingly, full-inorganic CsPbX3 PSCs have been garnering intensive

attention for applying in the optoelectronic devices. Although CsPbX3 PSCs possess good chemical stability, the PCE of the current full-inorganic PSCs are still lags behind of the hybrid halide perovskite based-PSCs. The main challenge to achieve high performance of CsPbX3 PSCs comes from that



the properties and stability are varied in different CsPbX3 structure, which lead to the change of the humidity tolerance and band gap.19-22 For example, α-phase CsPbI3 is extensive studied due to its favorable narrow bandgap (Eg = 1.73 eV) and the CsPbI3 PSC can obtain the champion PCE (17.06%) among the full-inorganic PSCs.16 However, α-phase CsPbI3 (black phase) can easily degrade to a non-perovskite δ-phase (yellow phase ， Eg = 2.82 eV) at room ambient; On the other hand, the CsPbBr3 PSCs have been fully demonstrated to have excellent stability even without any encapsulation.23 But CsPbBr3 light absorbing layer shows limit absorption range from 300 to 540 nm caused by its wide band gap (Eg = 2.3 eV), which lead to a lower PCE. Further, researchers start to focus on mixed inorganic halide perovskites (CsPbI3−xBrx). Brown cubic phase CsPbI2Br, with the narrow band gaps of 1.92 eV, shows better stability and higher phase transition temperature than CsPbI3, however, it still severely suffers from high-humidity/temperature attacking.13 Fortunately, the stability can be greatly improved by increasing bromide ions in CsPbI3−xBrx. CsPbIBr2 not only can keep long-term stability in the air environment, but also has a suitable band gap (Eg = 2.05 eV). It appears to be the best choice after balancing the band gap and stability features of all the interested full-inorganic perovskites. Up to now, the optimal PCE of CsPbIBr2 PSC has achieved 9.16%.24 But its PCE still inferior to the devices using organic-inorganic hybrid perovskite, and even other CsPbX3 materials. Further efforts in preparation and optimization of CsPbIBr2 devices are in urgently necessary. To effectively enhance the photovoltaic performance of CsPbIBr2 PSCs, some


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issues should be considered. First, the prepared technology for full-inorganic perovskite layers is normally one-step or two-step solution route without assistance of any anti-solvent. As a consequence, relatively low-quality of CsPbX3 films with a large amount of grain boundaries and compositional defects were obtained, which easily cause charge recombination in grain boundaries of the resulting cells.25-26 Note that these low-quality CsPbX3 films were proved to be easily mixed with the upper hole transport layer (HTL, such as spiro-OMETAD), which can further cause the charge recombination in another way.27 In addition, D. McGehee et al. revealed that the perovskite mixed with I and Br could degrade into I-rich (low-bandgap) or Br-rich (high-bandgap) domains due to the light-induced halide phase segregation (Hoke effect).28 This phenomenon leads to the deterioration of the device performance, which is another important issue should be considered. Utilizing anti-solvent assistant strategy and interface engineering have been considered to be the effective strategies to improve the film quality and device performance in the case of hybrid PSCs.29-32 Especially, Li et al. and Wang et al. successfully synthesized high-quality CsPbI2Br films with the assistant of isopropanol anti-solvent. The champion PCE of 16.07% was achieved in the CsPbI2Br based PSCs.29 However, to the best of our knowledge, the precise control of crystal growth in CsPbIBr2 film is missing, especially in the views of anti-solvent and interface engineering. In this work, six different anti-solvents were used to precisely control the growth of CsPbIBr2 crystals to construct a high-quality full-inorganic film on TiO2 electron transport layer (ETL). Among six different anti-solvents, diethyl ether (DEE) was



found to be the best one, which could efficiently promote the crystallization of CsPbIBr2 film. On this basis, in order to further optimization interface between CsPbIBr2 film and spiro-OMETAD HTL layer, three different organic ions were further modified on the surface of CsPbIBr2 films, which were methylammonium (MA, CH3NH3+), formamidinium (FA, CH3(NH2)2+) and guanidinium (GA, CH6N3+). By comparing, the introduction of GA showed a stronger enhancement in device performance, this is because GA could more effectively passivate under-coordinated iodine species between adjacent crystalline grains. Consequently, we successfully achieved a highly performance CsPbIBr2 PSCs with a PCE as high as 9.17% which ranked in the highest PCE range in all the CsPbIBr2 PSCs. Due to the excellent film quality after proposed optimization, flexible and large area (225 mm2) device based on the CsPbIBr2 were fabricated with PCEs of 5.43% and 6.45%. Furthermore, this optimized strategy was successfully extended to other kinds of CsPbX3 PSCs, PCEs of 6.91% and 10.73% were achieved in case of CsPbI3 and CsPbI2Br PSCs, respectively.

2 Experiment section 2.1 Material preparation Methylammonium iodide (MAI), formamidinium iodide (FAI), guanidinium iodide (GAI) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were obtained from You Xuan Trade Co., Ltd. Barium iodide (CsI), lead iodide (PbI2), lead bromide (PbBr2), dimethylsulfoxide (DMSO), chlorobenzene (CB), isopropanol (IPA),


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dichloromethane (DCM), toluene (TOL), ethyl acetate (EAC), DEE, and tetrabutyl titanate

were

purchased

from

Sigma-Aldrich.

[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene

2,2',7,7'-Tetrakis

(Spiro-OMeTAD)

was

purchased from Xi’an Polymer Light Technology Corp. The other materials were purchased from Macklin Company. All the chemicals were used as accepted without further purification.

2.2 Device Fabrication. First, fluorine doped tin oxide (FTO) glass substrates were etched by zinc powder together with 2 M of HCl, and they were successively ultrasonic cleaned in FTO cleaning solution in deionized water, acetone, isopropanol, and ethanol solutions for 20 min, respectively, dried in nitrogen stream. The as-treated FTO substrates were further treated by UV ultraviolet ozone for 30 min to remove the surface organic residues before using. In order to prepare high quality TiO2 films by electron beam deposition technology, the TiO2 powder for preparing the target material of electron beam deposition was synthesized by a modified sol-gel method.33 The synthesis details are as follows: 1 mmol tetrabutyl titanate was added into a mixed solution composed by 10 mL of absolute ethanol, 0.1 mL of acetic acid, and 0.1 mL of hydrochloric acid, and stirred for 4 h at room temperature to acquire a clear and transparent liquid. The final solution was vacuum dried to powder in 80°C for 6 h followed by annealing in air at 500 °C for 4 h. Then, the target material was prepared by cold pressing TiO2 powder into a round bulk material for 20 minutes at room



temperature. Finally, uniform TiO2 powder was deposited on FTO or PET substrates by electron beam deposition equipment (Denton, Explorer). During the electron beam deposition process, the deposition chamber was evacuated to 1.0×10−5 Pa. The distance between the TiO2 target and the substrates was kept at 40 cm, the deposited time and evaporation rates were fixed at 30 min and 0.5 nm.s-1, respectively. Finally, uniform TiO2 ETLs with dense thickness of 50 nm were obtained. For the fabrication of perovskite layer, the whole process was performed in a nitrogen-protected glovebox. CsPbIBr2 precursor solution (1.0 M) was prepared by fully dissolving 259.81 mg of CsI and 367.01 mg of PbBr2 in 1 mL of methyl sulfoxide (DMSO) at room temperature and stirred for 3 h to completely dissolve the salts. Then, the CsPbIBr2 precursor solution was spin-coated on the TiO2 ETLs at 500 rpm for 10 s and 3000 rpm for 40 s, respectively. In this process, 400 μL of six different anti-solvents was dropped on the spinning films after 20 s of the second spinning program started, respectively. Note that the adopted anti-solvents are: CB, IPA, DCM, TOL, EAC, and DEE. Subsequently, the substrates were transferred onto a temperature controlling hotplate and heated at 35°C for 15 min. Note that the smaller radius of Cs+ (1.81 Å) usually results in a lower energy barrier and tends to intercalate between the PbBr2 frameworks during perovskite formation, this crystallization process can be completed at low temperature,34 such as 35°C in present case. The transparent films gradually changed to orange with heating. Subsequently, the desired bright red CsPbIBr2 films were obtained by increasing the heating temperature to 120°C for 60 min in order to remove the remnant solvent and further


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improve the crystallization quality of the perovskite thin film. For MAPbI3 perovskite layer, the precursor solution was prepared by dissolving 0.1589 g of CH3NH3PbI3 (MAI) and 0.4610 g of PbI2 (molar ratio of 1:1) in 1 mL of mixture solution of DMF and DMSO with the volume ratio of 7:3. The MAPbI3 solution was spin-coated on the c-TiO2 ETL with 1000 rpm for 10 s and 4000 rpm for 30 s, respectively. In this process, 100 μL of CB was dropped on the spinning films after 15 s of the second spinning program. Then, the substrates were annealed at 100 °C for 5 min in a nitrogen-protected glove box. Finally, organic iodized (I) salt (MAI, FAI, and GAI in isopropanol) solutions with different concentrations were spin-coated on the CsPbIBr2 film at 1500 rpm for 20 s, respectively. Then, the substrates were transferred onto the hotplate again with the temperature of 120°C for 5 min. Next, the Spiro-OMeTAD mixed solution (50 mg of Spiro-MeOTAD, 22.5 μL of 4-tert-butylpyridine, and 22.5 μL of acetonitrile solution containing 170 mg·mL-1 of lithium bis-(trifluoromethylsulfonyl)imide in 1 mL of chlorobenzene) was deposited on the surface of as-prepared CsPbIBr2 film by spin-coating at 3000 rpm for 30 s in the nitrogen atmosphere. Finally, the Au electrode with a thickness of 100 nm was deposited by thermal evaporation in a vacuum environment under 2 × 10 −4 Pa. For CsPbI3 and CsPbI2Br precursor solutions (1.0 M), they were prepared by fully dissolving 259.81 mg of CsI and 461.01 mg of PbI2 in 1 mL of DMSO, 259.81 mg of CsI, 183.51 mg of PbBr2, and 230.51 mg of PbI2 in 1 mL of DMSO at room temperature, respectively. The other processes for building PSCs were exactly the same as that of CsPbIBr2 PSCs.



3. Results and discussion 3.1 Structure and morphology

Figure 1. (a) Schematic illustration of the fabrication process of precisely controlled CsPbIBr2 film, (b) schematic device structure, and (c) energy level diagram of CsPbIBr2 PSCs.

The preparation process of the precise controlled CsPbIBr2 layer grown on the TiO2/FTO substrate was illustrated in Figure 1a. Herein, electron beam deposition was adopted to prepare TiO2 ETL, which can provide a uniform and dense substrate for the growth of CsPbIBr2 film and also can obtain a good ETL layer with excellent flexibility (Step A in Figure 1a).35 The top-view scanning electron microscope (SEM) image of TiO2 ETL was shown in Figure S1. Then, 0.1 mL of CsPbIBr2 precursor solution was spin-coated onto the TiO2 ETL with a speed variable process (Step B). During this process, precise controlled CsPbIBr2 films with various morphologies can be obtained with the assistance of six different anti-solvents (CB, IPA, DCM, TOL,


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EAC, and DEE, step C). To achieve further improved device performance, different amount of A site cation-based iodine salts, such as MAI, FAI and GAI solutions, were spin-coated onto the CsPbIBr2 films to passivate the perovskite surface and grain boundary defects (Step D). After heating stabilization process, the MAI/FAI/GAI modified CsPbIBr2 layers were formed on the top surface of CsPbIBr2 films which can enhance the performance and stability of the finial devices. Figure 1b shows the device structure of CsPbIBr2 PSC, consisting of FTO glass/TiO2/optimized CsPbIBr2/Spiro-OMeTAD/Au, whereas the CsPbIBr2 film fabricated as the full-inorganic light absorbing layer, the organic ions (MAI/FAI/GAI) applied to passivate the CsPbIBr2 film which is optimized by different anti-solvents, the Spiro-OMeTAD film is used as the HTL, and the Au electrodes coated as the anode. The corresponding energy-level diagrams are plotted in Figure 1c, which illustrates the energy level alignment for each layer in the proposed PSCs structure. To investigate the effect of organic ions to the CsPbIBr2 layer, ultraviolet photoelectron spectroscopy (UPS, Figure S2) and the optical absorption spectra (Figure S3) with or without the organic ions modification were measured to get accurate valence band (VB) and conduction band (CB) positions. Take optimized CsPbIBr2 film which is improved by DEE anti-solvent and surface modified by GAI as an example (as shown in Table S1), the minimum energy difference of CB between optimized GAI-CsPbIBr2 film and TiO2 ETL is clearly smaller than that of pristine CsPbIBr2 film, indicating a smaller energy loss of electron transfer from optimized CsPbIBr2 to TiO2 ETL.36 In addition, work function of optimized CsPbIBr2



was derived to be 4.48 eV, which is obviously larger than that of pristine CsPbIBr2 film (4.06 eV). Forming of larger work function of optimized CsPbIBr2 film is normally accompanied by the formation of a higher built-in potential between it and TiO2 ETL.37 This means a larger driving force for dissociation and transfer of photo generated carriers as well as a wider depletion region for efficient suppression of electron–hole recombination in ultimate cell.

Figure 2. SEM images of the CsbPbIBr2 films deposited on the TiO2/FTO substrates with different anti-solvents of (a1) CB, (b1) IPA, (c1) TOL, (d1) DCM, (e1) EAC, and (f1) DEE, the insets are the photos of the actual CsbPbIBr2 films on the TiO2/FTO substrates. (a2–f2) gives the corresponding cross-sectional SEM images.

As mentioned, the quality of the pristine CsbPbIBr2 films was first optimized by applying different kinds of anti-solvent during the spin-coating process. Figure 2a1-f1 shows all the surface morphologies of the CsbPbIBr2 films with six different anti-solvents (CB, IPA, DCM, TOL, EAC, and DEE). The SEM image of CsbPbIBr2 film without any anti-solvent is exhibited in Figure S4a, in which porous structure,


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poor coverage, and uneven surface can be observed. In comparison, after using the anti-solvent, the coverage and porosity of the perovskite film are improved. The porosity of the CsbPbIBr2 films with the anti-solvents of CB, IPA, DCM, TOL, EAC, and DEE is gradually reduced and the film coverage is also improved (as shown in the insets of Figure 2). Comparing the passivized effect of all the anti-solvents used in our case, CsbPbIBr2 film with DEE as the anti-solvent (DEE-CsbPbIBr2) exhibits the best morphology, which has a homogeneous, pin-hole free, and well-crystallized surface with dense packing grains in the range from 100 to 400 nm (Figure 2f1). The energy dispersive spectroscopy (EDS) mapping images of Cs, Pb, I, and Br elements in DEE-CsbPbIBr2 film are exhibits in Figure S5, in which the uniform distributions of all the elements can be observed. In addition, the whole CsbPbIBr2 film presents excellent film coverage on the TiO2/FTO substrate (2×2 cm2) with a dark red color uniform dispersed (the inset of Figure 2f1). The

cross-sectional

SEM

images

of

a

real

PSCs

device

(FTO

glass/c-TiO/CsPbIBr2/Spiro-OMeTAD/Au) with different anti-solvent in CsPbIBr2 layer are shown in Figure 2a2-f2. Due to the porous structure of CsbPbIBr2 films without (Figure S2b) or with CB, IPA, DCM, TOL, and EAC anti-solvents (Figure 2a2-e2), the surface Spiro-MeOTAD layers in those devices are immersed into CsbPbIBr2 layers with a certain depth, which will greatly hinder the extraction rate of holes and increase the carrier recombination,38 and thus deteriorate the performance of the PSCs. However, by correctly engineering an anti-solvent, especially the DEE solvent, uniform and dense CsbPbIBr2 film can be obtained (Figure 2f2), which can



greatly improve the interface integrity between light absorbing layer and HTL. In case of Figure 2f2, the thicknesses of TiO2, DEE-CsbPbIBr2 light absorbing layer, spiro-OMeTAD, and Au layer are determined to be 50, 450, 120, and 100 nm, respectively.

Figure 3. (a) XRD patterns, (b) UV-vis spectra, (c) normalized steady-state PL spectra, and (d) XPS spectra of CsbPbIBr2 films on TiO2/FTO substrate with different anti-solvents passivation.

Figure 3a displays the X-ray diffraction (XRD) patterns of the CsPbIBr2 films on the FTO with different anti-solvent processes. Apart two peaks from the FTO substrate (as marked as *), the other identified peaks in all the CsPbIBr2 films can be well indexed to the standard patterns of CsPbIBr2 in the cubic phase.39 With addition of the anti-solvents, the ratios of peak intensity between (100) and (200) increase with varying degrees (as listed in Table 1). The largest increased (100) peak intensity in DEE-CsbPbIBr2 compared to all the other films demonstrates that the grains in such film has the best orientation.40 This phenomenon suggests another superiority in microstructure when correctly choose the anti-solvent in CsPbIBr2 film preparation in


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addition to the grain size and crystallinity. Besides, other unfavorable phase and structures are successfully eliminated in the DEE-CsPbIBr2 film, demonstrating a high-purity and high-crystallinity CsPbIBr2 phase is successfully formed by the anti-solvent process. We proposed that the DEE anti-solvent could help to remove some of the structural defects and thus reduce charge recombination in the perovskite films.41 Table 1 Photovoltaic parameters of different CsPbIBr2 PSCs and the ratios of peak intensity between (100) and (200) in the corresponding XRD patterns of CsPbIBr2 film with different anti-solvents. Perovskite

JSC (mA cm-2)

VOC (V)

FF

PCE (%)

The ratios of peak intensity [(100)/(200)]

No anti-solvent TOL-CsPbIBr2

7.42 7.77

0.98 0.99

0.543 0.556

3.95 4.20

0.31 0.56

DCM-CsPbIBr2

8.31

1.00

0.557

4.63

0.57

CB-CsPbIBr2

8.62

1.01

0.568

4.95

0.55

IPA-CsPbIBr2

8.63

1.02

0.608

5.36

0.64

EAC-CsPbIBr2

8.64

1.02

0.656

5.79

0.65

DEE-CsbPbIBr2

9.26

1.03

0.661

6.30

0.67

MAI-DEE-CsPbIBr2 (20 mg·mL-1) FAI-DEE-CsPbIBr2 (20 mg·mL-1) GAI-DEE-CsPbIBr2 (20 mg·mL-1) GAI-DEE-CsPbIBr2 (5 mg·mL-1) GAI-DEE-CsPbIBr2 (15 mg·mL-1) GAI-DEE-CsPbIBr2 (25 mg·mL-1)

10.10

1.15

0.726

8.45

10.14

1.18

0.727

8.69

10.24

1.20

0.746

9.17

1 0.76 0.98 0.71

The optical properties of CsPbIBr2 films are investigated and compared to



further demonstrate the advantage of using an appropriate anti-solvent. As shown in the ultraviolet absorption (UV-vis) spectra in Figure 3b, all the CsPbIBr2 films obtained with the existence of the anti-solvents show stronger absorption to different extent. Among these, the absorption of DEE-CsPbIBr2 film is the strongest one, indicating the great improved film coverage and grain crystallinity. Note that the slightly lift-ups can be assigned to the influence of TiO2/FTO substrates, as we measured all the uv-abs curves on the same substrates, and this phenomenon can be observed in some previous studies.42-43 In addition, the PL spectra of the different CsPbIBr2 films are studied in Figure 3c. Compared to the pristine CsPbIBr2 film which has the highest PL intensity, the PL intensity is greatly impressed in case of DEE-CsPbIBr2 film. Considering the pure CsPbIBr2 phase with the existence of DEE anti-solvent, the reason for this phenomenon can be assigned to the effectively reduced carrier recombination. The XPS spectra for Cs (3d), Br (3p), I (3d), and Pb (4f) elements are shown in Figure 4d. The shifts of all the above mentioned elements can be clearly observed with adding different anti-solvents. For the spectra of Cs (3d) and I (3d) elements, the peak positions tend to shift to higher binding energy side, while the position of Br (3p) element inclines to move to the opposite side after introducing anti-solvents. Differing from the other elements, XPS spectra of Pb (4f) shows different shift direction when introduce different anti-solvents, however, the Pb (4f) position of DEE-CsbPbIBr2 almost reserves as a constant compared to that of the pristine CsbPbIBr2 film. The above results indicate that the anti-solvents may help to re-distribute electron density of the component elements due to the different binding


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energy between cations and anions in the CsbPbIBr2 films.44 The photovoltaic properties of above mentioned CsbPbIBr2 PSCs with different anti-solvents, such as short-circuit current (JSC), open circuit voltage (VOC), fill factor (FF), and PCE, are measured (Figure S6) and summarized in Table 1. As compared, the improved film coverage and grain crystallinity of the CsPbIBr2 film with anti-solvents leads to the obviously increase of JSC and FF values and a slightly increase VOC. As a consequence, the PCEs of the corresponding PSCs are improved 6-59% when applied different anti-solvents. Especially in case of the DEE-CsPbIBr2 PSC, the PCE can reach to 6.30% compared to 3.95% of that of the pristine CsPbIBr2 device.

Figure 4 SEM images of the (a1) MAI-DEE-CsPbIBr2, (b1) FAI-DEE-CsPbIBr2, and (c1) GAI-DEE-CsPbIBr2 films. The insets are the results of water droplet contact angle measurements. (a2-c2)

the

corresponding

cross-sectional

SEM

images

of

as-prepared

PSC

using

MAI/FAI/GAI-DEE-CsPbIBr2 films. (d) EDS elemental mapping images of Cs, Pb, I, Br, C, and



Page 18 of 41

N in GAI-DEE-CsPbIBr2 film. (e) UV-vis and (f) PL spectra of GAI-DEE-CsPbIBr2 and control films measured from the structure of FTO/TiO2/perovskite layer.

It has been proved that appropriately introduce small amount of organic ions on the surface of perovskite layer can effectively improve the film uniformity and compactness, thus reduce the carriers recombination at interfaces.27,

35, 45-47

Herein,

surface organic ions modification strategy is further applied to precision control the quality of CsPbIBr2 layer optimized by DEE anti-solvent. Three common A-cation organic iodized solutions (20 mg.mL-1 in isopropanol), such as MAI, FAI and GAI, are chosen for investigating the influence on the film quality, structure, and even photovoltaic performance of the CsPbIBr2 layer. As seen from the SEM images (Figure 4a1-c1), the film uniformity and compactness of DEE-CsPbIBr2 films are obviously improved after the surface passivation by organic iodide, the grain sizes gradually increases when MAI (450 nm), FAI (650 nm), and GAI (950 nm) modification are applied on the CsPbIBr2 films. Compared to the DEE-CsPbIBr2 film (250 nm, Figure 2f1), the grain sizes are increased 2.25, 3.25, and 4.75 times, respectively. Among these, GAI modification can get the best improvement in film quality; the corresponding DEE-CsPbIBr2 film appears to possess higher grain continuity with fewer small grain protrusions and less prominent grain boundaries (Figure 4c1). It has been proved that larger GA cations could restrain the formation of iodide vacancies and inactivation the undercoordinated iodine species in bulk and at grain boundaries by hydrogen bonding.48-49 The corresponding cross-sectional SEM images are exhibited in Figure 4a2-c2. The organic ions solution (in isopropanol) can


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gradually reach the bottom of the film with a reduced concentration through the grain gaps,50-51 resulting in different morphology of the bottom films. In our case, the GAI-DEE-CsPbIBr2 film is more compact than those using other two organic ions, and this result is consistent with the corresponding SEM results in Figure 4a1-c1. In addition, the corresponding EDS mapping of GAI-DEE-CsPbIBr2 film is shown in Figure 4d. Comparing to the EDS mapping of DEE-CsPbIBr2 film (Figure S5), C and N elements originated from GAI are evenly distributed on the film. Atomic force microscopy (AFM) was conducted to measure the surface profiles of the MAI/GAI/FAI-DEE-CsPbIBr2 films (Figure S7). Consisting with the above results, GAI-DEE-CsPbIBr2 film shows a reduction in surface roughness (root mean square, RMS=3.249 nm) in comparison to 3.349 nm of FAI-DEE-CsPbIBr2 and 6.701 nm of MAI-DEE-CsPbIBr2 films. In addition, with applying different organic ions, the water contact angles are also increased from 38.7o to 59.1o from MAI to GAI passivation. This phenomenon can be attributed to two factors: First one is the high film quality due to the secondary growth process of the CsPbIBr2 grains with the introduction of large guanidinium cation;52 second one is the reduced grain boundaries due to the filling of GAI into the grain boundary.4 These results effectively avoided the direct contact between perovskite and water, which improved the hydrophobicity of the CsPbIBr2 film.35, 53-54 To further investigate the film quality improvement due to the organic macromolecular

passivation,

the

cross

section

images

of

PSCs

using

MAI/FAI/GAI-DEE-CsPbIBr2 layer are investigated in Figure 4a2-c2. The dense and



uniform

CsPbIBr2

films

can

be

observed,

and

Page 20 of 41

the

thicknesses

of

the

MAI/FAI/GAI-DEE-CsPbIBr2 films are similar (around 450 nm), which shows no obvious change in contrast to CsPbIBr2 film (Figure 2f2). Furthermore, the UV-vis and PL spectra of organic macromolecular passivation CsPbIBr2 films are studied in Figure 4e and f. As compared, under the structure of FTO/TiO2/perovskite layer, GAI-DEE-CsPbIBr2 films shows stronger absorption and weak fluorescence intensity, which mainly benefits from the higher crystallinity and film quality, thus reduces film defects and depresses carrier recombination process. In addition, the time-resolved PL (TRPL) curves of the control and GAI-DEE-CsPbIBr2 films on TiO2/FTO quenching layer are exhibited in Figure S8. Both the two decay curves can be fitted by a biexponential function.51 The decreased decay time of GAI-DEE-CsPbIBr2 film on the TiO2/FTO quenching layer indicates that GAI-DEE modified CsPbIBr2 film can reduce the defect density and thus enhance the charge separation and collection.37, 55-56

Figure 5 SEM images of DEE-CsPbIBr2 films used (a–d) 5, 15, 20, 25 mg·mL-1 solutions of GAI in isopropanol, respectively. e) Statistic grain sizes and f) XRD patterns of DEE-CsPbIBr2 films prepared with the 5, 15, 20, 25 mg·mL-1 solutions of GAI in isopropanol, respectively


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As studied, GAI-DEE-CsPbIBr2 film presents the best film quality and device performance among the three chosen organic ions, the influence of DEE-CsPbIBr2 films treated with different concentrations of GAI are further investigated. First, the SEM images of GAI-DEE-CsPbIBr2 films passivated by 5, 15, 20, 25 mg·mL-1 of GAI in isopropanol, respectively, are shown in Figure 5a–d. According to the corresponding grain size distribution (Figure 5e), DEE-CsPbIBr2 film treated with 20 mg·mL-1 GAI solution is conductive to achieve larger (950 nm) and more uniformed grains. When further increase the concentration of GAI solution to 25 mg·mL-1, the grain size reduces to 850 nm due to excess GA+ causing a deterioration of the crystallinity and affect the growth of the film.48 XRD patterns of different GAI-DEE-CsPbIBr2 films are shown in Figure 5f. No other miscellaneous phase can be observed. The ratios of peak intensity of (100) and (200) are calculated and listed in Table 1. As compared, the (100) peak intensities gradually become stronger compared to that of naked DEE-CsPbIBr2 film when the concentration of GAI solution increased from 5 to 20 mg·mL-1. The peak intensity ratio of (100) and (200) reaches 1 in case of 20 mg·mL-1, indicating gradually improved film crystallinity and crystal orientation. Then, the intensity decreases when the concentration of GAI solution is further increased to 25 mg.mL-1, this result is agreed with those in the corresponding SEM images (Figure 5a-d).



3.2 Device performance

Figure 6 (a) J–V curves (under simulated AM 1.5 G illumination) of PSC using GAI-DEE-CsPbIBr2 film and the control device. (b) and (c) statistic PCE, JSC, VOC, and FF distributions of 20 of PSCs using GAI-DEE-CsPbIBr2 film and the control device. (d) steady-state (measured at voltage bias of 0.8 V), (e) IPCE spectra, (f) dark J–V curves, (g) VOC values versus light intensity and the linear fitting curves, (h) time-dependent variations of normalized PCEs in room temperature condition, and (i) normalized PCEs continuously heated at 100oC of GAI-DEE-CsPbIBr2 PSC and the control device.

To confirm the influence of different organic ions passivation on the performance of


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the photoactive layer, the J-V characteristics of corresponding PSCs are measured in Figure S9. The relevant photovoltaic parameters including PCE, JSC, VOC, and FF are compared and summarized in Table 1. In order to determine the trap-state density of CsPbIBr2 with different anti-solvents, the dark J−V curves of electron only devices with a structure of FTO/TiO2/CsPbIBr2/PCBM/Au were investigated. In Figure S10a, low voltage region and high voltage region in the dark J−V curves represent the Ohmic region and the space-charge limited current (SCLC) region, respectively.57-58 The intersection between these two regions can determine the trap-filled limit voltage (VTFL), and as the bias voltage reaches to this intersection point, the trap state will be completely filled.59 Among all the studied electron devices, only the device using DEE-CsPbIBr2 film displays a clear VTFL, while the other devices all display fuzzy distinction point between these two regions. This result can be assigned to the high porosity of the CsPbIBr2 films using other different anti-solvents (as proved in Figure 2) which leads to the bad contact of the PCBM layer in the corresponding devices, and it further demonstrates the highly improved film quality of DEE-CsPbIBr2 film. Due to the effective improvement of uniformity and compactness of DEE-CsPbIBr2 film, the photovoltaic performances of all the CsPbIBr2 PSCs using organic ions passivated strategy are significantly improved (Table 1), the PCE values improved by 34.1%, 37.9%, and 45.6% for MAI/FAI/GAI-DEE-CsPbIBr2 PSCs, respectively, compared to the naked DEE-CsPbIBr2 PSC. We also prepared four electron devices using

GAI-DEE-CsPbIBr2,

FAI-DEE-CsPbIBr2,

MAI-DEE-CsPbIBr2

and

DEE-CsPbIBr2 (control device) and studied their defect densities. The dark J−V



curves of the electron devices are shown in Figure S10b. Normally, the relationship between VTFL and the trap-state density can be estimated according to the following equation: 𝑉𝑇𝐸𝐿 =

𝐿2 𝑒𝑛𝑡 2𝜀𝜀0

Where e is the charge of one electron, ε is the dielectric constant of CsPbIBr2 (8)56, ε0 is the vacuum permittivity, nt is the defect density, and L is the thickness of the perovskite film. As seen, the nt value positively correlates with that of VTFL in our case since the thickness of the studied perovskite films are the same (as proved in Figure 4). The VTFL values of the GAI-DEE-CsPbIBr2, FAI-DEE-CsPbIBr2, MAI-DEE-CsPbIBr2 and control devices are calculated to be 0.84V, 0.92V, 0.98V and 1.03V, respectively. And the defect density (nt) of the GAI-DEE-CsPbIBr2, FAI-DEE-CsPbIBr2, MAI-DEE-CsPbIBr2 and control devices are tested to be 3.67× 10-17 cm-3, 4.02×10-17 cm-3, 4.28×10-17 cm-3 and 4.50×10-17 cm-3, respectively. The lower trap density of the GAI-DEE-CsPbIBr2 perovskite indicates the highly improved film quality after GAI modification in CsPbIBr2 film. Furthermore, statistic PCEs of GAI-DEE-CsPbIBr2 PSCs post-treated with 5, 15, 20, 25 mg·mL-1 GAI solutions were compared in Figure S11, it is clear that GAI-DEE-CsPbIBr2 (20 mg·mL-1) PSC can achieve the highest PCE in our case. Since the PSC using GAI-DEE-CsPbIBr2 (20 mg·mL-1) film achieved the champion performance among all the devices studied in this work, series characterizations about device performance focused on this cell are performed and compare with the control device (the DEE-CsPbIBr2 PSC) in the following study.


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Figure 6a presents the comparison of typical J–V curves of the GAI-DEE-CsPbIBr2 PSC with the control device, and the statistic PCE, JSC, VOC, and FF distributions of 20 PSCs are summarized in Figure 6b and c. The GAI-DEE-CsPbIBr2 PSC shows a highest PCE of 9.17% with the JSC of 10.24 mA cm-2, VOC of 1.20 V, and FF of 74.6%. All the device performance metrics increases markedly in case of GAI-DEE-CsPbIBr2 PSC. A comparison of PCEs of all the reported CsPbIBr2 PSCs as far as we know and GAI-DEE-CsPbIBr2 PSC in our work is listed in Table S2. Overall, the designed PSC in our work shows a high PCE among all the reported all-inorganic cells. Note that the highest PCE value of CsPbIBr2 PSC by adjusting the properties of the light absorbing layer is 9.16%, it was reported by Zhu et. al who adopted intermolecular exchange strategy by introducing CsI solution.60 Very recently, Subhani et. al achieved the champion PCE value of CsPbIBr2 PSC of 10.88% by optimizing the structure of PSC, they inserted a SmBr3 layer between CsPbIBr2 and TiO2 films to enhance the interface interaction.56 As compared, this PCE value is ranked in the highest PCE range in CsPbIBr2 PSCs which focus on the improvement of CsPbIBr2 layer itself reported so far. Figure 6d shows the stabilized JSC output of the champion PSC under continuous AM 1.5G illumination for 250 s. Consisting with the J–V measurements, the JSC is determined to be 9.14 mA cm-2 for the GAI-DEE-CsPbIBr2 PSC after continuous measuring for 250 s, which is much higher than the control device (7.62 mA·cm-2). In addition, obvious descending trend can be observed for the control device in the same measurement condition due to the light induced halide phase segregation in naked perovskite film. Figure 6e provides



the corresponding IPCE spectra. Across the absorption range from 300 to 600 nm, the GAI-DEE-CsPbIBr2 PSC exhibits higher light absorption ability. It achieves the highest IPCE value of 87% compared to the control device (72%), indicates that the champion PSC possesses enhanced photoelectric conversion property. Figure 6f shows dark J–V curves of the champion PSC and control device to investigate the photovoltaic properties. The GAI-DEE-CsPbIBr2 PSC exhibits significantly smaller dark current from 0 to 1 V and leak current from -0.5 to 0 V than that of the control device, which is beneficial to the improvement of its VOC. To further confirm the effect of reduced intrinsic defect density on charge recombination behavior in the devices, the dependences of VOC on various light intensities are shown in Figure 6g. Normally, a slope of VOC versus light intensities equal to n(kBT/q) suggests only bimolecular charge recombination, whereas kB is the Boltzmann constant, T is the absolute temperature, and q is the elementary charge. When the slope is higher than kBT/q suggests defect-mediated recombination.61 In our case, the slope of the control device is estimated to be 1.40 kBT/q, while it is decreased to 1.27 kBT/q for the champion PSC. This result indicates that defect-mediated recombination dominated the charge loss in these devices, and GAI surface passivation can effectively weaken this charge recombination. In addition, the electrical impedance spectroscopy (EIS) were performed to study the recombination resistances as a function of the perovskite film after passivation, which were measured at 0.8 V under dark conditions with frequency range from 1 to 100000 Hz. The inset is the adopted simulated equivalent circuit (Figure S12). In the equivalent circuit, RS, Rreb, and Creb


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present series resistance of metal contact, recombination resistance, and chemical capacitance,

respectively.

Normally,

larger

Rreb

suggests

smaller

carriers’

recombination in the light absorbing layer. As shown in Figure S12, the Rreb value (1142.3 Ω) of the GAI-DEE-CsPbIBr2 PSC is much bigger than that of the control device (725.8 Ω), indicating that the optimal interface contact and decreased carrier recombination between GAI-CsPbIBr2 layer and the c-TiO2 ETL and leading to an increase of VOC and FF.55 The long-term stability curves of the two studied PSCs measured in high humidity ambient are exhibited in Figure 6h. After 25 days exposure in room temperature (25oC, 40% humidity), the PCE of control device retains 85% of its initial value, which could be further enhanced to 90% for the GAI-DEE-CsPbIBr2 PSC. Typically, the defects both at the interface and in the bulk of the CsPbIBr2 films are considered to be a critical factor for triggering their moisture-assisted decomposition, this result well agrees with the AFM and XRD results that the appropriate introduced of GAI can effectively improve the quality of the CsPbIBr2 film. In addition, the stability of the champion PSC in our case are further compared with the MAPbI3 PSC which is the most popular and intensive studied hybrid perovskite. As shown in Figure 6i, under the measurement condition (air atmosphere with 10% humidity), the GAI-DEE-CsPbIBr2 PSC also possesses excellent robustness against oxygen even after continuous heating at 100oC for 100 h and the PCE of the cell almost keeps constant. However, the MAPbI3 PCE quickly dropped down to 15% of the initial value. The superior thermal stability of GAI-DEE-CsPbIBr2 PSC presents a huge



Page 28 of 41

prospect for the commercial applications.

Figure 7 (a) J-V curve of the flexible GAI-DEE-CsPbIBr2 (20 mg.mL-1) PSC based on PET substrate. The background is the corresponding photograph and the inner table lists the corresponding VOC, JSC, FF, and PCE values. (b) PCEs and photographs of GAI-CsPbIBr2 (20 mg.mL-1) PSC based on FTO substrate with different active areas (2×5, 5×5, 10×10 and 15×15 mm2, respectively).

Due to the significantly improved film quality and the enhanced device performance of GAI-DEE-CsPbIBr2 (20 mg.mL-1) PSC as well as the good flexibility of c-TiO2 ETL thin film fabricated by the electron beam deposition, a flexible PSC device was further constructed and investigated (Figure 7a). The structure of the flexible PSC is PET/c-TiO2/GAI-DEE-CsPbIBr2/spiro-OMeTAD/Au. The best flexible PSC has a PCE of 5.43% with the JSC of 9.04 mA cm-2, VOC of 1.09 V, and FF of 0.551. In addition, the different large-area (up to 225 mm2) devices with the structure

of

FTO/c-TiO2/GAI-DEE-CsPbIBr2/spiro-OMeTAD/Au

are

also

investigated. Figure 7b exhibits the PCEs and the corresponding photographs of the PSCs with different active area and the average PCEs are estimated to be 9.17%,


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8.51%, 7.88%, and 6.41% for the PSCs with effective area of 2×5, 5×5, 10×10, and 15×15 mm2, respectively. The decreased PCEs can be assigned to the introduction of more surface defects with increasing the effective area. The successful fabrication of the flexible and large area GAI-DEE-CsPbIBr2 PSCs shows promising prospect in the practical application. To demonstrate the universality of our strategy, we applied the anti-solvent control strategy to other kinds of full-inorganic PSCs, such as CsbPbI2Br and CsbPbI3 based devices (Figure S13). The corresponding photovoltaic parameters are listed in Table S3. All the full-inorganic PSCs can achieve the highest performance when applied DEE as an anti-solvent. The PCEs can reach 8.74% in CsPbI2Br PSCs (5.51% in pristine CsPbI2Br PSC) with improved JSC and FF values. In case of CsPbI3 PSCs, the highest PCE is 5.58% (3.90% in pristine CsPbI3 PSC) because the obviously increased JSC, VOC, and FF values. Similar like the optimization of CsPbIBr2 PSCs, the surface organic ions passivated strategy are extended to the CsPbI2Br and CsPbI3 PSCs. The effectiveness of the GAI post-treatment is also suitable for these two kind of inorganic perovskite layer, the PCEs are improved by 22.8% and 23.8% for CsPbI2Br and CsPbI3 PSCs, respectively (Figure S14 and Table S3). In addition, the time-dependent variations of normalized PCEs for PSCs using CsPbI2Br and CsPbI3 in room temperature (25oC) with 40% humidity are shown in Figure S15. After 120 and 60 h, the PCEs of GAI-DEE-CsPbI2Br PSC can retain 90% and 65% of its initial value, respectively, while the control device only can maintain 70% and 41% of its initial value. For GAI-DEE-CsPbI3 PSC, the PCE drops to 50% after 10 h, however,



the PCE of control device quickly drops to 0% only after 20 h. The above results further confirm the practicality of as-designed strategies.

4. Conclusions In summary, the anti-solvents and organic ions surface passivation strategies were successfully applied to precisely control the growth of CsPbIBr2 crystals. The chosen of appropriate anti-solvents and organic ions both showed great influence on the quality of CsPbIBr2 film. As a result, high-quality CsPbIBr2 film by selecting DEE as the anti-solvent and GAI as the surface passivated organic ions was obtained. Herein, DEE was used to improve the film coverage, crystallization, homogeneous, and packing way of the grains as well as restrain the formation of the pin-holes, while GAI was applied to assist the secondary growth of the CsPbIBr2 film, which could suppress the formation of iodide vacancies and inactivation the undercoordinated iodine species in bulk and at grain boundaries. The constructed planer GAI-DEE-CsPbIBr2 PSC exhibited an optimal PCE of 9.17% with all the device performance metrics increases markedly. This PCE is ranking in the highest PCE range of the existing CsPbIBr2 PSCs and it is significantly improved by 132% and 45.6% compared to that of the pristine CsPbIBr2 PSC (3.95%) and DEE-CsPbIBr2 PSC (6.30%) in this case. Besides, the stability was greatly enhanced compared to the DEE-CsPbIBr2 PSC and the most studied MAPbI3 PSC in air ambient with 40% humidity and after 100oC heat treatment. On this basis, the flexible devices with a PCE of 5.43% and different large area device (up to 225 mm2) with a PCE of 6.14%


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were also successfully achieved. In addition, the anti-solvents and organic ions surface passivation strategies were further applied to other kind of full-organic PSCs. This work provides a new avenue for preparation highly efficient and stable all-inorganic PSCs for the practical applications.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. The top-view SEM of electron beam evaporated TiO2 ETL on the FTO substrate, the UPS spectra of CsPbIBr2 and GAI-CsPbIBr2 perovskite films deposited on TiO2/FTO substrates, ultraviolet visible absorption spectra of the CsPbI2Br and CsPbI3 films with different anti-solvents, table of band energies of CsbPbIBr2 and GAI-CsbPbIBr2 films determined by the UV-visible absorption spectra and UPS analysis, SEM of the CsbPbIBr2 perovskite films deposited on TiO2/FTO substrate without any anti-solvent and its cross-section SEM view, EDS elemental mapping of Cs, Pb, I, and Br elements in CsPbIBr2 thin film with DEE as the anti-solvent, J-V curves of the CsPbIBr2 PSCs using with different anti-solvents, AFM profiles of the (a) MAI-DEE-CsPbIBr2, (b) FAI-DEE-CsPbIBr2 and (c) GAI-DEE-CsPbIBr2 films, the TRPL decay curves of the control and GAI-DEE-CsPbIBr2 films on the TiO2/FTO quenching layer, J-V curves of the CsPbIBr2 PSCs with different organic macromolecule passivation, the electron mobility measured from the J-V traces of the



CsbPbIBr2 films with different anti-solvent and DEE-CsbPbIBr2 films with different organic macromolecule passivation, statistic PCE distributions of GAI-DEE-CsPbIBr2 PSCs using different concentration of GAI in IPA solution, table of PCEs of all the reported CsPbIBr2 PSCs in the literatures and in this work, EIS curves of the PSC using (20 mg.mL-1) and the control device measured under dark conditions, J-V curves of the PSCs using CsPbI2Br, CsPbI3 films with different anti-solvents, table of Parameters of different CsPbI2Br and CsPbI3 PSCs, J-V curves of the CsPbI2Br and CsPbI3 PSCs with different organic macromolecular passivation, and time-dependent variations of normalized PCE for CsPbI2Br and CsPbI3 PSCs devices in room temperature (25oC) with 40% humidity.

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (L. X.). *E-mail: [email protected] (H. W. S.). Author Contributions All authors have approved the final version of the manuscript. Notes The authors declare no competing financial interest.

ACKNOWLEGEMENTS This work was supported by the National Key Research and Development Program


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(2016YFC0207101), the Key Program of NSFC-Guangdong Joint Funds of China (U1801253), the National Natural Science Foundation of China (Grant Nos. 11874181, 11674126, 61822506, 61874049, 61775080, 11674127, 61674067), the Special Project of the Province-University Co-constructing Program of Jilin Province (SXGJXX2017-3), the Jilin Province Natural Science Foundation of China (No. 20180101210JC, 20170101170JC, 20160418055FG).



REFERENCE (1) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Il Seol, S., Solvent Engineering for High-Performance Inorganic-Organic Hybrid Perovskite Solar Cells. Nature Materials 2014, 13,

897-903. (2) Xing, G.; Mathews, N.; Lim, S. S.; Yantara, N.; Liu, X.; Sabba, D.; Grätzel, M.; Mhaisalkar,

S.; Sum, T. C., Low-Temperature Solution-Processed Wavelength-Tunable Perovskites for Lasing. Nature materials 2014, 13, 476-480. (3) Arora, N.; Dar, M. I.; Hinderhofer, A.; Pellet, N.; Schreiber, F.; Zakeeruddin, S. M.; Grätzel,

M., Perovskite Solar Cells with CuSCN Hole Extraction Layers Yield Stabilized Efficiencies Greater than 20%. Science 2017, 358, 768-711. (4) Deying Luo, W. Y., Zhiping Wang, Aditya Sadhanala, Qin Hu, Rui Su, Ravichandran

Shivanna, Gustavo F. Trindade, John F. Watts, Zhaojian Xu, Tanghao Liu, Ke Chen, Fengjun Ye, Pan Wu, Lichen Zhao, Jiang Wu, Yongguang Tu, Yifei Zhang, Xiaoyu Yang, Wei Zhang, Richard H. Friend, Qihuang Gong, Henry J. Snaith, Rui Zhu1,, Enhanced Photovoltage for Inverted Planar Heterojunction Perovskite Solar Cells. Science 2018, 360, 1442-1446. (5) Michael M. Lee, J. T., Henry J. Snaith, Efficient Hybrid Solar Cells Based on

Meso-Superstructured Organometal Halide Perovskites. Science 2012, 338, 643-647. (6) Samuel D. Stranks, G. E. E., Giulia Grancini,Christopher Menelaou,Marcelo J. P. Alcocer,

Tomas Leijtens,Laura M. Herz,Annamaria Petrozza,Henry J. Snaith1, Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber. Science 2013, 324, 342-343. (7) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. I., Solvent Engineering for High-Performance Inorganic–Organic Hybrid Perovskite Solar Cells. Nature Materials 2014, 13,

897-903. (8) Ball, J. M.; Lee, M. M.; Hey, A.; Snaith, H. J., Low-Temperature Processed Meso-Superstructured to Thin-Film Perovskite Solar Cells. Energy & Environmental Science 2013,

6 , 1739-1743. (9) Bryant, D.; Aristidou, N.; Pont, S.; Sanchez-Molina, I.; Chotchunangatchaval, T.; Wheeler, S.;

Durrant, J. R.; Haque, S. A., Light and Oxygen Induced Degradation Limits the Operational Stability


Page 34 of 41

Page 35 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of Methylammonium Lead Triiodide Perovskite Solar Cells. Energy & Environmental Science 2016, 9, 1655-1660. (10) Han, Y.; Meyer, S.; Dkhissi, Y.; Weber, K.; Pringle, J. M.; Bach, U.; Spiccia, L.; Cheng,

Y.-B., Degradation Observations of Encapsulated Planar CH3NH3PbI3 Perovskite Solar Cells at High Temperatures and Humidity. Journal of Materials Chemistry A 2015, 3 , 8139-8147.

(11)

Li, W.; Zhang, W.; Van Reenen, S.; Sutton, R. J.; Fan, J.; Haghighirad, A. A.; Johnston, M.

B.; Wang, L.; Snaith, H. J., Enhanced UV-Light Stability of Planar Heterojunction Perovskite Solar Cells with Caesium Bromide Interface Modification. Energy & Environmental Science 2016, 9 , 490-498. (12) Zhang, X.; Ren, X.; Liu, B.; Munir, R.; Zhu, X.; Yang, D.; Li, J.; Liu, Y.; Smilgies, D.-M.; Li, R.; Yang, Z.; Niu, T.; Wang, X.; Amassian, A.; Zhao, K.; Liu, S., Stable High Efficiency Two-Dimensional Perovskite Solar Cells Via Cesium Doping. Energy & Environmental Science 2017, 10 , 2095-2102. (13) Mariotti, S.; Hutter, O. S.; Phillips, L. J.; Yates, P. J.; Kundu, B.; Durose, K., Stability and Performance of CsPbI2Br Thin Films and Solar Cell Devices. ACS Appl Mater Interfaces 2018, 10 , 3750-3760. (14) Lu, J.; Chen, S.-C.; Zheng, Q., Defect Passivation of CsPbIBr2 Perovskites for High-Performance Solar Cells with Large Open-Circuit Voltage of 1.28 V. ACS Applied Energy Materials 2018, 1 , 5872-5878. (15) Guo, Z.; Teo, S.; Xu, Z.; Zhang, C.; Kamata, Y.; Hayase, S.; Ma, T., Achievable High Voc of Carbon based All-Inorganic CsPbIBr2 Perovskite Solar Cells through Interface Engineering. Journal of Materials Chemistry A 2019, 7 , 1227-1232. (16) Wang, Y.; Zhang, T.; Kan, M.; Zhao, Y., Bifunctional Stabilization of All-Inorganic alpha-CsPbI3 Perovskite for 17% Efficiency Photovoltaics. J Am Chem Soc 2018, 140, 12345-12348. (17) Duan, J.; Hu, T.; Zhao, Y.; He, B.; Tang, Q., Carbon-Electrode-Tailored All-Inorganic Perovskite Solar Cells To Harvest Solar and Water-Vapor Energy. Angew Chem Int Ed Engl 2018, 57 , 5746-5749. (18) Liang, J.; Zhao, P.; Wang, C.; Wang, Y.; Hu, Y.; Zhu, G.; Ma, L.; Liu, J.; Jin, Z., CsPb0.9Sn0.1IBr2 Based All-Inorganic Perovskite Solar Cells with Exceptional Efficiency and Stability. J Am Chem Soc 2017, 139 , 14009-14012.



(19) Sutton, R. J.; Eperon, G. E.; Miranda, L.; Parrott, E. S.; Kamino, B. A.; Patel, J. B.; Hörantner, M. T.; Johnston, M. B.; Haghighirad, A. A.; Moore, D. T.; Snaith, H. J., Bandgap-Tunable Cesium Lead Halide Perovskites with High Thermal Stability for Efficient Solar Cells. Advanced Energy Materials 2016, 6 , 1502458. (20) Ahmad, W.; Khan, J.; Niu, G.; Tang, J., Inorganic CsPbI3 Perovskite-Based Solar Cells: A Choice for a Tandem Device. Solar RRL 2017, 1, 1700048. (21) Bai, D.; Zhang, J.; Jin, Z.; Bian, H.; Wang, K.; Wang, H.; Liang, L.; Wang, Q.; Liu, S. F., Interstitial Mn2+-Driven High-Aspect-Ratio Grain Growth for Low-Trap-Density Microcrystalline Films for Record Efficiency CsPbI2Br Solar Cells. ACS Energy Letters 2018, 3, 970-978. (22) Begum, R.; Parida, M. R.; Abdelhady, A. L.; Murali, B.; Alyami, N. M.; Ahmed, G. H.; Hedhili, M. N.; Bakr, O. M.; Mohammed, O. F., Engineering Interfacial Charge Transfer in CsPbBr3 Perovskite Nanocrystals by Heterovalent Doping. Journal of the American Chemical Society 2017, 139, 731-737. (23) Lau, C. F. J.; Deng, X.; Zheng, J.; Kim, J.; Zhang, Z.; Zhang, M.; Bing, J.; Wilkinson, B.; Hu, L.; Patterson, R.; Huang, S.; Ho-Baillie, A., Enhanced Performance Via Partial Lead Replacement with Calcium for a CsPbI3 Perovskite Solar Cell Exceeding 13% Power Conversion Efficiency. Journal of Materials Chemistry A 2018, 6, 5580-5586. (24) Weidong Zhu, Q. Z., Dazheng Chen, Zeyang Zhang, Zhenhua Lin, Jingjing Chang, Jincheng Zhang, Chunfu Zhang, and Yue Hao, Intermolecular Exchange Boosts Efficiency of Air-Stable, Carbon-Based All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells to Over 9%. Adv. Energy Mater 2018, 8, 1802080. (25) Hu, Y.; Bai, F.; Liu, X.; Ji, Q.; Miao, X.; Qiu, T.; Zhang, S., Bismuth Incorporation Stabilized α-CsPbI3 for Fully Inorganic Perovskite Solar Cells. ACS Energy Letters 2017, 2, 2219-2227. (26) Luo, P.; Zhou, Y.; Xia, W.; Zhou, S.; Liu, J.; Lu, Y.; Xu, C.; Sun, L., Colorful, bandgap-tunable, and air-stable CsPb(IxBr1-x)3 Inorganic Perovskite Films Via a Novel Sequential Chemical Vapor Deposition. Ceramics International 2018, 44 , 12783-12788. (27) Li, B.; Zhang, Y.; Fu, L.; Yu, T.; Zhou, S.; Zhang, L.; Yin, L., Surface Passivation Engineering Strategy to Fully-Inorganic Cubic CsPbI3 Perovskites for High-Performance Solar Cells. Nature Communications 2018, 9, 1076-1084. (28) Bush, K. A.; Frohna, K.; Prasanna, R.; Beal, R. E.; Leijtens, T.; Swifter, S. A.; McGehee, M. D., Compositional Engineering for Efficient Wide Band Gap Perovskites with Improved Stability to


Page 36 of 41

Page 37 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Photoinduced Phase Segregation. ACS Energy Letters 2018, 3, 428-435. (29) Chen, W.; Chen, H.; Xu, G.; Xue, R.; Wang, S.; Li, Y.; Li, Y., Precise Control of Crystal Growth for Highly Efficient CsPbI2Br Perovskite Solar Cells. Joule 2019, 3, 191-204. (30) Anaraki, E. H.; Kermanpur, A.; Steier, L., Highly Efficient and Stable Planar Perovskite Solar Cells by Solution-Processed Tin Oxide. Energ. Environ. Sci. 2016, 9, 3128-3134. (31) Chang, H.; Wang, G.; Yang, A.; Tao, X.; Liu, X.; Shen, Y.; Zheng, Z., A Transparent, Flexible, Low-Temperature, and Solution-Processible Graphene Composite Electrode. Advanced Functional Materials 2010, 20 , 2893-2902. (32) Chen, H.; Liu, D.; Wang, Y.; Wang, C.; Zhang, T.; Zhang, P.; Sarvari, H.; Chen, Z.; Li, S., Enhanced Performance of Planar Perovskite Solar Cells Using Low-Temperature Solution-Processed Al-Doped SnO2 as Electron Transport Layers. Nanoscale Research Letters 2017, 12, 238-244. (33) Baorang Li, X. W., Minyu Yan, Longtu Li, Preparation and Characterization of Nano-TiO2 Powder. Materials Chemistry and Physics 2002, 78, 184–188. (34) Chong Liua, W. L., Jianhui Chenb, Jiandong Fana,, Yaohua Maia,b, Ruud E.I. Schropp, Ultra-thin MoOx as Cathode Buffer Layer for the Improvement of All-Inorganic CsPbIBr2 Perovskite Solar Cells. Nano Energy 2017, 41, 75–83. (35) Chen, C.; Liu, D.; Wu, Y.; Bi, W.; Sun, X.; Chen, X.; Liu, W.; Xu, L.; Song, H.; Dai, Q., Dual Interfacial Modifications by Conjugated Small-Molecules and Lanthanides Doping for Full Functional Perovskite Solar Cells. Nano Energy 2018, 53, 849-862. (36) Peng, J.; Duong, T.; Zhou, X.; Shen, H.; Wu, Y.; Mulmudi, H. K.; Wan, Y.; Zhong, D.; Li, J.; Tsuzuki, T.; Weber, K. J.; Catchpole, K. R.; White, T. P., Efficient Indium-Doped TiOx Electron Transport Layers for High-Performance Perovskite Solar Cells and Perovskite-Silicon Tandems. Advanced Energy Materials 2017, 7, 1601768. (37) Chen, C.; Li, H.; Jin, J.; Cheng, Y.; Liu, D.; Song, H.; Dai, Q., Highly Enhanced Long Time Stability of Perovskite Solar Cells by Involving a Hydrophobic Hole Modification Layer. Nano Energy 2017, 32, 165-173. (38) Zheng, X.; Lei, H.; Yang, G.; Ke, W.; Chen, Z.; Chen, C.; Ma, J.; Guo, Q.; Yao, F.; Zhang, Q.; Xu, H.; Fang, G., Enhancing Efficiency and Stability of Perovskite Solar Cells Via a High Mobility P-Type PbS Buffer Layer. Nano Energy 2017, 38, 1-11. (39) Liu, C.; Li, W.; Chen, J.; Fan, J.; Mai, Y.; Schropp, R. E. I., Ultra-thin MoOx as Cathode Buffer



Layer for the Improvement of All-Inorganic CsPbIBr2 Perovskite Solar Cells. Nano Energy 2017, 41, 75-83. (40) Hu, M.; Bi, C.; Yuan, Y.; Bai, Y.; Huang, J., Stabilized Wide Bandgap MAPbBrxI3-x Perovskite by Enhanced Grain Size and Improved Crystallinity. Adv Sci (Weinh) 2016, 3, 1500301. (41) Ramírez Quiroz, C. O.; Levchuk, I.; Bronnbauer, C.; Salvador, M.; Forberich, K.; Heumüller, T.; Hou, Y.; Schweizer, P.; Spiecker, E.; Brabec, C. J., Pushing Efficiency Limits for Semitransparent Perovskite Solar Cells. Journal of Materials Chemistry A 2015, 3, 24071-24081.

(42) Baker, J.; Hooper, K.; Meroni, S.; Pockett, A.; McGettrick, J.; Wei, Z.; Escalante, R.; Oskam, G.; Carnie, M.; Watson, T., High throughput Fabrication of Mesoporous Carbon Perovskite Solar Cells. Journal of Materials Chemistry A 2017, 5 , 18643-18650. (43) Pan, D.; Fan, H.; Li, Z.; Wang, S.; Huang, Y.; Jiao, Y.; Yao, H., Influence of Substrate on Structural Properties and Photocatalytic Activity of TiO2 Films. Micro & Nano Letters 2017, 12 , 82-86. (44) Zhao, Y.; Wang, Y.; Duan, J.; Yang, X.; Tang, Q., Divalent Hard Lewis Acid Doped CsPbBr3 Films for 9.63%-Efficiency and Ultra-Stable All-Inorganic Perovskite Solar Cells. Journal of Materials Chemistry A 2019, 7, 6877-6882.

(45) Leguy, A. M. A.; Frost, J. M.; McMahon, A. P.; Sakai, V. G.; Kockelmann, W.; Law, C.; Li, X.; Foglia, F.; Walsh, A.; O’Regan, B. C.; Nelson, J.; Cabral, J. T.; Barnes, P. R. F., The Dynamics of Methylammonium Ions in Hybrid Organic–Inorganic Perovskite Solar Cells. Nature Communications 2015, 6, 7124-7134.

(46) Zhang, X.; Liu, C.; Li, J.; He, Y.; Li, Z.; Li, H.; Shen, L.; Guo, W.; Ruan, S., Unraveling the Effect of Polymer Dots Doping in Inverted Low Bandgap Organic Solar Cells. Physical Chemistry Chemical Physics 2015, 17, 16086-16091.

(47) Zhang, C.-C.; Li, M.; Wang, Z.-K.; Jiang, Y.-R.; Liu, H.-R.; Yang, Y.-G.; Gao, X.-Y.; Ma, H., Passivated Perovskite Crystallization and Stability in Organic–Inorganic Halide Solar Cells by Doping a Donor Polymer. Journal of Materials Chemistry A 2017, 5, 2572-2579.

(48) De Marco, N.; Zhou, H.; Chen, Q.; Sun, P.; Liu, Z.; Meng, L.; Yao, E. P.; Liu, Y.; Schiffer, A.; Yang, Y., Guanidinium: A Route to Enhanced Carrier Lifetime and Open-Circuit Voltage in Hybrid Perovskite Solar Cells. Nano Lett 2016, 16 , 1009-1016.

(49) He, J.; Fang, W.-H.; Long, R.; Prezhdo, O. V., Increased Lattice Stiffness Suppresses


Page 38 of 41

Page 39 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Nonradiative Charge Recombination in MAPbI3 Doped with Larger Cations: Time-Domain Ab Initio Analysis. ACS Energy Letters 2018, 3, 2070-2076.

(50) Niu, T.; Lu, J.; Munir, R.; Li, J.; Barrit, D.; Zhang, X.; Hu, H.; Yang, Z.; Amassian, A.; Zhao, K.; Liu, S. F., Stable High-Performance Perovskite Solar Cells via Grain Boundary Passivation. Adv Mater 2018, 30 (16), e1706576. (51) Tripathi, N.; Shirai, Y.; Yanagida, M.; Karen, A.; Miyano, K., Novel Surface Passivation Technique for Low-Temperature Solution-Processed Perovskite PV Cells. ACS Appl Mater Interfaces 2016, 8 (7), 4644-4650. (52) Wang, S.; Zhu, Y.; Sun, W.; Miao, X.; Ma, Z.; Yang, C.; Liu, B.; Li, S.; Ma, R.; Wang, C., Large Guanidinium Cation Enhance Photovoltage for Perovskite Solar Cells Via Solution-Processed Secondary Growth Technique. Solar Energy 2018, 176, 118-125.

(53) Qingsen Zeng, X. Z., Xiaolei Feng, Siyu Lu, Zhaolai Chen, Xue Yong, Simon A. T. Redfern, Haotong Wei, Haiyu Wang, Huaizhong Shen, Wei Zhang, Weitao Zheng, Hao Zhang, John S. Tse, and Bai Yang, Polymer-Passivated Inorganic Cesium Lead Mixed-Halide Perovskites for Stable and Efficient Solar Cells with High Open-Circuit Voltage over 1.3 V. Adv Mater 2018, 30, 1705393. (54) Zhang, J.; Jin, Z.; Liang, L.; Wang, H.; Bai, D.; Bian, H.; Wang, K.; Wang, Q.; Yuan, N.; Ding, J.; Liu, S. F., Iodine-Optimized Interface for Inorganic CsPbI2Br Perovskite Solar Cell to Attain High Stabilized Efficiency Exceeding 14. Adv Sci (Weinh) 2018, 5 , 1801123. (55) Jin, J.; Li, H.; Chen, C.; Zhang, B.; Xu, L.; Dong, B.; Song, H.; Dai, Q., Enhanced Performance of Perovskite Solar Cells with Zinc Chloride Additives. ACS Applied Materials & Interfaces 2017, 9, 42875-42882.

(56) Subhani, W. S.; Wang, K.; Du, M.; Wang, X.; Liu, S., Interface ‐ Modification ‐ Induced Gradient Energy Band for Highly Efficient CsPbIBr2 Perovskite Solar Cells. Advanced Energy Materials 2019, 9, 1803785.

(57) Hawash, Z.; Ono, L. K.; Qi, Y., Moisture and Oxygen Enhance Conductivity of LiTFSI-Doped Spiro-MeOTAD Hole Transport Layer in Perovskite Solar Cells. Advanced Materials Interfaces 2016, 3, 1600117.

(58) Saidaminov, M. I.; Abdelhady, A. L.; Murali, B.; Alarousu, E.; Burlakov, V. M.; Peng, W.; Dursun, I.; Wang, L.; He, Y.; Maculan, G.; Goriely, A.; Wu, T.; Mohammed, O. F.; Bakr, O. M.,



High-quality Bulk Hybrid Perovskite Single Crystals within minutes by Inverse Temperature Crystallization. Nat Commun 2015, 6, 7586-7596.

(59) Ye, S.; Rao, H.; Yan, W.; Li, Y.; Sun, W.; Peng, H.; Liu, Z.; Bian, Z.; Li, Y.; Huang, C., A Strategy to Simplify the Preparation Process of Perovskite Solar Cells by Co-deposition of a Hole-Conductor and a Perovskite Layer. Adv Mater 2016, 28, 9648-9654.

(60) Harikesh, P. C.; Wu, B.; Ghosh, B.; John, R. A.; Lie, S.; Thirumal, K.; Wong, L. H.; Sum, T. C.; Mhaisalkar, S.; Mathews, N., Doping and Switchable Photovoltaic Effect in Lead-Free Perovskites Enabled by Metal Cation Transmutation. Adv Mater 2018, 30, e1802080.

(61) Duan, J.; Zhao, Y.; He, B.; Tang, Q., High-Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency. Angew Chem Int Ed Engl 2018, 57, 3787-3791.


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Planer PSC using the optimal CsPbIBr2 film and electron beam deposited TiO2 compact layer exhibits a PCE of 9.17%.


High Performance CsPbIBr2 Perovskite Solar Cells - ACS Publications

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