Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13

Subscriber access provided by READING UNIV

Article

Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13% Efficiency Owning to the Optimization of CH3NH3PbI3-xClx Film via H2O Additive Yangyang Du, Hongkun Cai, Xichang Bao, Zhixue Xing, Yunhao Wu, Jian Xu, Like Huang, Jian Ni, Juan Li, and Jianjun Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03382 • Publication Date (Web): 07 Nov 2017 Downloaded from http://pubs.acs.org on November 7, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24

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

ACS Sustainable Chemistry & Engineering

Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13% Efficiency Owning to the Optimization of CH3NH3PbI3-xClx Film via H2O Additive Yangyang Du, † Hongkun Cai, †* Xichang Bao, §* Zhixue Xing, † Yunhao Wu, † Jian Xu, † Like Huang, † Jian Ni, † Juan Li, † Jianjun Zhang† †

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071, China, E-mail address:[email protected]

*†

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071, China, E-mail address: [email protected] §

CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China, E-mail address:

[email protected] †

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071,

†


China, E-mail address:[email protected] China, E-mail address:[email protected] †

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071, China, E-mail address:[email protected]

†


†


China, E-mail address: [email protected] China, E-mail address: [email protected] †

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071, China, E-mail address: [email protected]

†

College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300071, China, E-mail address: [email protected]

ACS Paragon Plus Environment


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

ABSTRACTS: In this work, flexible perovskite solar cells (F-PSCs) are fabricated utilizing the device polyethylene terephthalate (PET) substrate/ITO/PEDOT:PSS /CH3NH3PbI3-xClx/PCBM/Ag, which exhibit the optimal power conversion efficiency (PCE) reaching 13.27%, superb stability against bending deformation and advantageous stability in ambient atmosphere without encapsulation. Meanwhile, we herein confirm a fact that incorporating suitable H2O additive into the perovskite precursor solution leads to an enhanced CH3NH3PbI3-xClx perovskite quality for F-PSCs application including the improvement of morphology and electrical properties. To better summarize the mechanism concerning how H2O additive affects the perovskite film quality, CH3NH3PbI3-xClx films are prepared by a simple one-step spinning method from a solution containing CH3NH3I, PbI2, and PbCl2 in a mixed solvent of H2O and dimethyl formamide (DMF) with solely various volume ratio ranging from 0.1% to 0.9%. Through a comparative analysis, it is proposed that H2O additive prolongs the CH3NH3PbI3-xClx recrystallization process contributing to slower crystallization rate. Additionally, it can merge adjacent perovskite grain together by accelerating the diffusion of ions within the pre-deposited films toward grain boundary, and thereby yielding large and densely-packed perovskite grain size. KEYWORDS: Flexible perovskite solar cells (F-PSCs), H2O additive, PET substrate, crystallization, stability. █

INTRODUCTION Perovskite materials possess a high extinction coefficient over the visible spectrum and low

exciton binding energy, which make them superior light harvesters for photovoltaic applications.1-4


Page 2 of 24

Page 3 of 24

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


In addition, due to their nearly meeting all the requirements for an idea solar cell technology, such as low-cost fabrication,5-7 abundant material resources,8 high power conversion efficiency (PCE),9 perovskite solar cells (PSCs) have currently become one of the most dramatic research topics in the field of solar cells. The PCE of PSCs only owned 3.9% when it was reported for the first time in 2009.8 However, its value has currently skyrocketed to 22.1% despite of only a few years.10 Meanwhile, a fact that versatile design of device architectures allow for PSCs application has been unveiled.6,11,12 And some efforts devoted to observe the mechanisms of perovskite film growth and PSCs work are also implemented.12-17 Flexible perovskite solar cells (F-PSCs), as a vital member of PSCs group, can be easily moulded into different shapes, and can be integrated with infrastructures of various shapes and sizes for innovative energy-generating products, which also receive extensive attention with the development of PSCs.18-23 Compared to their counterparts that are fabricated on glass substrates (G-PSCs), F-PSCs often possess some additional merits including flexible, lightweight, portable and curved surfaces. As a consequence, developing F-PSCs should be considered a suitable and exciting arena both from the manufacturing view point or that of applications. Although tremendous advances have been gained for the studying of F-PSCs, still most F-PSCs efficiency values severely lag behind their counterparts of G-PSCs, which have been reported with PCEs only in the range of 2-18%.18-25 Yang et al. claim that they obtain F-PSCs on PET substrate with PCE of 9.2% by adopting a low-temperature processing technique to product TiO2 photo-anode.18 Bolink et al. also prepare F-PSCs on PET substrate possessing maximum PCE of 7%.19 Dai and colleagues have reported the fabrication F-PSCs on PET substrate by layer-by-layer growth method, giving a 12.25% PCE value.20 More recently, Yoo and colleagues state that



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

F-PSCs on plastic substrate with the highest PCE of 13.3% are successfully made by replacing TiO2 layer with C60.22 Carefully observing the reported findings, it is unveiled that the main drawbacks for low PCE of F-PSCs should be attributed to the failure of high-quality CH3NH3PbI3-xClx growth on flexible substrate (especially PET substrate). As we know, controllable growth of perovskite film is regarded as the most important factor to obtain high-efficiency PSCs. This criterion is also applied to F-PSCs working mechanism. The boundaries of the multi-crystalline perovskite grains and the defects within the grain are proposed to the imperfection of the perovskite film, which cause energy loss by non-radiative recombination, and therefore decreasing the PCE value of corresponding cell.26,27 To better control the morphology and crystallization of perovskite films and thereby obtaining high-efficiency PSCs, many efforts have been attempted in the study of G-PSCs. In particular, some additives are introduced into the perovskite precursor solution, such as DIO, HI, PCBM, etc.,28-31 which can be able to control the crystallization behavior during the process of perovskite formation by accelerating the perovskite nucleation rate or retarding their crystallization rate. On the other hand, it is a fact that perovskite materials are closely dependent on the fabrication conditions (especially moisture), which makes it difficult to fabricate PSCs in ambient conditions, and seriously hindering their industrialization.32-34 In general, it is a challenge to obtain a smooth and uniform perovskite films under high humidity. Inspired by the previous reports, we here report on efficient F-PSCs employing the optimized CH3NH3PbI3-xClx films prepared by introducing H2O additive into perovskite precursor solution that exhibit both high PCE reaching 13% and stability, alone with negligible hysteresis influence. The CH3NH3PbI3-xClx films are produced in a single spin-coating step from a solution containing


Page 4 of 24

Page 5 of 24

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


CH3NH3I, PbCl2 and PbI2 in a mixed solvent containing H2O and DMF, whose volume ratio (VRH O/DMF) is solely varied from 0% to 0.9%. Compared to the reference sample (without any 2

H2O additive), CH3NH3PbI3-xClx film fabricated by VRH O/DMF=0.5% possesses superior 2

characteristics including smooth surface morphology, larger grain size, and reduced defect density. In addition, when applied to F-PSCs fabrication, the improved CH3NH3PbI3-xClx film can not only facilitate the impediment of shunting current loss, but also boost the enhancement of charge collection by suppressing photo-generated carrier recombination via non-radiative path. Furthermore, the mechanism concerning how H2O additives affect perovskite growth is also proposed. The findings in this work provide a route to further promote perovskite quality and a clue to achieve the high-efficient F-PSCs fabrication.

Figure 1. (a) Overall device structure illustration including PET/ITO/PEDOT:PSS /CH3NH3PbI3-xClx/PCBM/Ag. (b) The corresponding cross-section scanning electron microscope (SEM) image of F-PSCs construction. (c) Actual picture of our F-PSCs. █

EXPERIMENTAL METHODS Device fabrication. The ITO-coated glass and PET were sequentially cleaned using detergent,

acetone, and ethanol. Before following operation, the rinsed substrates were further treated with ultraviolet and ozone for 20 min. Then, around 100 nm hole transport layer was deposited on the cleaned substrates by spin-coating the filtered PEDOT:PSS precursor solution (4083) (0.22 um filters) at 4000 rpm for 40 s and drying at 120 ℃ for 20 min. After that, the prepared substrates were transferred to glovebox. To prepare perovskite films, PbI2, PbCl2 and CH3NH3I were mixed into H2O/DMF solvent with the molar ratio of 1:1:4 and stirred above 12 h for the fabrication of



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

45 wt% perovskite precursor solution. And the prepared perovskite precursor solution was spin-coated on PET (glass)/ITO/PEDOT:PSS substrates at 2500 rpm for 45s to form the pre-deposited light capture layer. In contrast, the VRH O/DMF of perovskite precursor solution was 2

solely changed from 0%, 0.1%, 0.3%, 0.5%, 0.7% and 0.9%. Sequentially, the pre-deposited films were immediately dried on a hotplate at 100 ℃ for 60 min to form the remnant CH3NH3PbI3-xClx films. Then, an organic PCBM layer was deposited on the PET (or glass)/ITO/PEDOT:PSS /CH3NH3PbI3-xClx substrate by spin coating PCBM in chlorobenzene (15 mg ml-1) at 1500 rpm for 40 s. Finally, 100 nm of silver was deposited by thermal evaporation using a shadow mask to pattern the electrodes. The whole schematic image and cross-section scanning electron microscope (SEM) image of our F-PSCs device were shown in Figure 1a and Figure 1b, respectively. Meanwhile, a product picture was displayed in Figure 1c. And the dot area of p-PSCs was 0.06 cm2. With regard to the G-PSCs fabrication, all the technological processes were identical except the difference of substrate for comparison.

Characterization. Current density-voltage curves were measured using a solar simulator under one-sun illumination (100 mw cm-2 AM 1.5G). J-V curves of all devices were conducted by masking the active area with a metal mask. The external and quantum efficiency (EQE) spectrum was tested to determine the photoelectric response of devices. The steady-state current density measurement for F-PSCs was operated to ensure F-PSCs performance in actual conditions (VersaSTAT 4). The AFM measurement was obtained using a scanning probe multimode instrument with a tapping mode size of 5*5 um2. The surface morphology of CH3NH3PbI3-xClx films was observed by scanning electron microscope (SEM) (Hitachi SU8010). Absorption spectra of CH3NH3PbI3-xClx films were recorded on a shimadzu UV-2550 spectrophotometer. The


Page 6 of 24

Page 7 of 24

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


steady-state photoluminescence (PL) measurement was recorded using a steady-state fluorescence spectrometer (FL3-2-IHR221-NIR-TCSPC). The crystallization and phase identification of the CH3NH3PbI3-xClx films were performed by X-ray diffraction (XRD) (Philips PANalytical X’Pert Pro, Cu Kα). The hall measurement was probed to determine the conductivity ability for glass/ITO and PET/ITO, respectively. █

RESULTS AND DISCUSSION

Figure 2. (a) The J-V curves of F-PSCs consisting of PET/ITO/PEDOT:PSS/CH3NH3PbI3-xClx /PCBM/ Ag as the variation of VRH O/DMF in perovskite precursor solution detected by voltage scanning from reverse direction (Voc to Jsc). (b) Corresponding EQE measurements. 2

Table 1. The photovoltaic parameters extracted from Figure 2a Samples

Voc (V)

Jsc (mA/cm2)

FF (%)

PCE (%)

AV-PCE (%)

VRH O/DMF=0% VRH O/DMF=0.1% VRH O/DMF=0.3% VRH O/DMF=0.5% VRH O/DMF=0.7% VRH O/DMF=0.9%

0.90 0.92 0.94 0.95 0.86 0.76

18.84 19.10 19.46 19.82 14.60 9.75

63.0 63.7 63.9 70.5 60.7 52.8

10.69 11.20 11.69 13.27 7.63 3.91

8.74 9.38 10.01 11.69 5.62 1.80

2

2

2

2

2

2

Firstly, the F-PSCs based on structure illustrated in Figure 1 were fabricated. And Figure 2a showed the current density-voltage (J-V) characteristics of F-PSCs, where the voltage sweep rate was 20 mV s-1 and the sweep direction was from reverse direction (Voc to Jsc). To better investigate the device performance for different recipe in this work and obtain precise result, the statistics analysis for each related device on a basis of 36 devices was conducted and the average PCE (AV-PCE) was displayed. All the relevant photovoltaic parameters were summarized in Table 1.



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

Page 8 of 24

On the basis of the results shown in Table 1, it was observed that F-PSCs performance was so dependent on the variation of VRH O/DMF. The reference device (VRH O/DMF =0%) exhibited a PCE 2

2

of 10.69% (AV-PCE of 8.74%) with open circuit voltage (Voc) of 0.90 V, short-circuit current density (Jsc) of 18.84 mA/cm2 and fill factor (FF) of 63%. For VRH O/DMF >0.5%, the device 2

performance deteriorated considerably. However, in the range of VRH O/DMF=0.1%-0.5%, the 2

whole device photovoltaic parameters substantially increased compared to reference device, reaching a maximum PCE of 13.27% (AV-PCE of 11.69%) at VRH O/DMF =0.5%. During the rise of 2

FF and Jsc, Voc maintained large value around 0.94, indicating that suitable H2O additive did not destroy charge collection efficiency. The improvement of short circuit current density (Jsc) was moreover verified by the external quantum efficiency (EQE) measurements (shown in Figure 2b) exhibiting uniform tendency measured by J-V curves. However, when the recipe of VRH O/DMF 2

exceeded 0.5%, EQE response became obviously weak, especially in the long wavelength range (600-800 nm). In our case, the difference between all specimens was only the difference of VRH O/DMF for CH3NH3PbI3-xClx films fabrication. Hence, it was rationalized that the promoted 2

device performance was closely related to the variation of perovskite quality. It was well documented that CH3NH3PbI3-xClx crystalline affected charge generation, transport, and recombination behaviors; and that the perovskite grain boundary was the major charge recombination rate.12,16,26,27


Page 9 of 24

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


Figure 3. (a) The J-V curves of F-PSCs and G-PSCs consisting of ITO/PEDOT:PSS /CH3NH3PbI3-xClx /PCBM/ Ag at VRH O/DMF =0.5%, where the voltage sweep rate was 20 mV s-1 and the sweep direction was both from reverse direction (Voc to Jsc) and forward direction (Jsc to Voc). (b) Corresponding EQE measurements and steady-state current density as the time variation. 2

Table 2. The photovoltaic parameters extracted from Figure 3a Samples

Voc (V)

Jsc (mA/cm2)

FF (%)

PCE (%)

AV-PCE (%)

F-PSCs and RS F-PSCs and FS G-PSCs and RS G-PSCs and FS

0.95 0.94 1.05 1.05

19.82 19.73 21.45 21.25

70.5 69.8 71.8 69.8

13.27 12.95 16.18 15.58

11.69 11.39 14.66 14.05

Apart from PCE, the challenges for F-PSCs development were basically made up of two aspects. One was that their performance usually gravely lagged behind that of G-PSCs.18,20 Even though the identical technological process was performed, there also existed enormous difference in device performance. It is therefore that we also compared the optimal device performance for F-PSCs and G-PSCs in our case, respectively. The other one was that hysteresis in J-V curves under different bias sweep directions emerged as an important issue in the accurate characterization of F-PSCs.35,36 In order to further observe these problems in our F-PSCs, we scanned the representative devices both from the reverse direction (Voc to Jsc) and forward direction (Jsc to Voc) and the corresponding photovoltaic parameters were summarized in Table 2. As shown in Figure 3a (or Table 2), the results highlighted no significant hysteresis was observed in both devices, indicating good reliability of the obtained data. Besides, it could be noted that the highest PCEs of F-PSCs and G-PSCs were 13.27% and 16.18% respectively, which clearly stated a weak PCE gap between two types of devices. Moreover, to further probe the device performance under more realistic conditions, the steady-state power output for F-PSCs and G-PSCs were also probed, respectively. The devices were kept at the maximum power point (as determined from the J-V curves from Figure 3a) and the photocurrents were recorded as a function of time (shown in Figure 3b). The stabilized photocurrent of G-PSCs was found to be 21.39 mA/cm2, whereas it was



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

measured to be 20.68 mA/cm2 for F-PSCs. This observation, alone with AV-PCE value (shown in Table 2), reinforced the idea that the optimal F-PSCs here obtained a decent exhibition with diminutive difference of device performance between F-PSCs and G-PSCs. Here, we believed that the weak PCE difference might be mainly caused by two aspects. First of all, the conductivity measurements for PET and glass substrates were carried out. As shown in Figure S1 and Figure S2, a higher conductivity for glass/ITO substrate facilitated the decrease of device series resistance, and thereby resulting in higher FF. Secondly, the perovskite quality grown on glass based substrate had larger grain size compared to that grown on PET based substrate (shown in Figure S3)., which should be attributed to the inferior substrate surface morphology of PET/ITO determined by AFM measurements (shown in Figure S4 and Figure S5). Combined with the above discussions, it was assumed that suitable H2O incorporated into perovskite precursor solution did only strongly influence the composition and optical absorption of the remnant CH3NH3PbI3-xClx films. On the contrary, while controlling the VRH O/DMF in the range of 0.1% to 0.5%, the improvement of FF 2

with VRH O/DMF increasing should be ascribed to enhanced perovskite quality. As we know, a 2

favorable CH3NH3PbI3-xClx film that possess suitable thickness, pinhole-free morphology, high-crystalline, and large grain size, often plays a crucial role in PSCs perovskite. Therefore, it was implied that VRH O/DMF =0.5% could provide a positive effect on perovskite quality. 2


Page 10 of 24

Page 11 of 24

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


Figure 4. Atomic force microscope (AFM) images of the CH3NH3PbI3-xClx films upon PET/ITO/PEDOT:PSS substrates with increasing the VRH O/DMF value from 0% to 0.9%. 2

Figure 5. Scanning electron microscope (SEM) images of the CH3NH3PbI3-xClx upon PET/ITO/PEDOT:PSS substrate with increasing the VRH O/DMF value from 0% to 0.9%. Their high resolution images were shown as insets. 2

To substantiate our assumption about the reason for F-PSCs performance enhancement, the surface morphologies of CH3NH3PbI3-xClx based on various VRH O/DMF were primarily 2

investigated. As shown in Figure 4, the AFM images of perovskite films revealed that the root-mean-square (RMS) roughness of perovskite films originally decreased and then increased with the raise of VRH O/DMF. A smoother perovskite surface was a better foundation for the 2

subsequent PCBM growth contributing to the improvement of PCBM morphology. Also, a smoother perovskite surface could form a better electronic contact with the upper PCBM layer due



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

Page 12 of 24

to the decreased interfacial defect state density. Obviously, the RMS of CH3NH3PbI3-xClx film fabricated by VRH O/DMF=0.5% had the optimal result around 16 nm, consistent with the above 2

discussion. Meanwhile, the grain size variation was further investigated by the cross section images derived from corresponding AFM linecuts. It was estimated that the grain size of perovskite films were increased from 705.5nm to 2.6 um with the variation of VRH O/DMF=0%-0.5%, alone with continuous grain morphology. However, for VRH O/DMF>0.5%, 2

2

the continuity of perovskite film was ruined. It implied that VRH O/DMF=0.5% was indeed a strict 2

condition for the fabrication of well performed perovskite film, agreeing well with the results displayed in Table 1. In addition, the morphology variation for perovskite films with the change of VRH O/DMF was further validated by SEM (shown in Figure 5). It was disclosed that 2

CH3NH3PbI3-xClx films were continuous and fully covered on PET/PEDOT:PSS when VRH O/DMF 2

was less than 0.5%. Nevertheless, while the VRH O/DMF exceeded 0.7%, some holes on the films 2

were initially observed, which contributed to the poor continuity observed in AFM image. Combined with the results exhibited in Figure 4 and Figure 5, the CH3NH3PbI3-xClx film with the best quality (largest grains, a very smooth surface and no pinholes) was obtained when the VRH O/DMF was kept at 0.5%. Large perovskite crystallite exhibited a reduced area of grain 2

boundaries, and thereby causing the overall density of defect states was low. Much of the carrier recombination through defects via non-radiative mean was suppressed and whereas emission originating from band-to-band recombination was strengthened.


Page 13 of 24

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


Figure 6. (a) Absorbance spectra of CH3NH3PbI3-xClx films as a function of VRH O/DMF variation; (b) Corresponding steady-state photoluminescence (PL) spectra. 2

Furthermore, the UV/Vis absorption spectra and steady-state photoluminescence (PL) measurements were carried out to figure out the decreased defect state density in CH3NH3PbI3-xClx films via H2O-assisted deposition. As shown in Figure 6a, the absorption intensities of films in the visible light range were all qualitatively similar, consisting of intense absorption bands below 500 nm and a sharp band edge feature at 780 nm. With increasing VRH O/DMF value in the range of 0.7% to 0.9%, a small but steady decrease in the optical density of 2

the films was observed, exhibiting a same tendency with the EQE variation. It should be attributed to the presence of some pinholes causing the increase of optical transmission. However, when the VRH O/DMF was in the range of 0%-0.5%, the absorption characteristics of perovskite films was not 2

seriously affected, suggesting that the improved device performance did not contribute to the increased optical absorption. Therefore, the effect of the film thickness on the variation of the photovoltaic could be ruled out. Besides, the enhanced PL spectra of CH3NH3PbI3-xClx films (shown in Figure 6b) indicated that the non-radiative carrier recombination was significantly suppressed in the bulk of CH3NH3PbI3-xClx films to some extent. When VRH O/DMF was less than 2

0.5%, their absorption characteristic was nearly approaching. Having eliminated the influence of optical absorption on PL intensity, it was therefore that the enhanced fluorescence should be



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

Page 14 of 24

attributed to the reduced non-radiative recombination. For VRH O/DMF=0.7% or 0.9%, the decline 2

PL intensity might correlate with two considerations. Firstly, their corresponding absorption was lower. Besides, the high VRH O/DMF value indeed deteriorated the perovskite film. In a word, it 2

suggested that the bulk defect in perovskite films could be reduced compared to the reference sample while VRH O/DMF was 0.5%. 2

Figure 7. The normalized X-ray diffraction (XRD) pattern of the CH3NH3PbI3-xClx upon PET/ITO/PEDOT:PSS substrate as the function of VRH O/DMF value ranging from 0% to 0.9%. (a) Before annealing; (b) After annealing. 2

Figure 8. Schematic illustration of the different morphology development for CH3NH3PbI3-xClx films with and without H2O additive. To better clarify the effects of H2O additive on the perovskite morphology and why such a distinct change occurs in PL spectroscopy, XRD of the studied CH3NH3PbI3-xClx thin films was investigated to analyze phase composition before and after thermal annealing. As shown in Figure 。

7a, for the pre-deposited wet perovskite films, all the films showed diffraction signals at 14.11


Page 15 of 24

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


。

and 28.43 belonging to (110) and (220) planes of the tetragonal perovskite phase. However, by further observation, diffraction peaks at 13.99

。

and 28.18

。

close to tetragonal perovskite phase

were also obviously noted. In stark contrast, these diffraction signals completely vanished when the wet film suffered from thermal annealing process (shown in Figure 7b). As we know, the introduction of Cl ingredient usually possessed distinctly slow crystallization compared with pure PbI2 system.3,12,16,17 Hence, we here denoted the two diffraction peaks as an indication of intermediate phase during the formation of CH3NH3PbI3-xClx to slow down the crystallization rate of perovskite film and control morphology. And the result displayed in Figure 7a indicated the coexistence of intermediate and perovskite crystallites in the as-cast wet films. Unfortunately, the detailed composition of intermediate phase was still ambiguous, which did not be similar to the result reported by Zhou et al. or other reported finding for the best of our knowledge.3 。

Furthermore, when the VRH O/DMF was 0.9%, there obviously existed PbI2 phase at 12.11 , 2

implying the presence of perovskite degeneration. This could be related with a fact that high moisture resulted in the formation of (CH3NH3)4PbI6 2H2O that irreversibly degraded the ●

perovskite film.34,37 Instead, after thermal annealing (shown in Figure 7b), the signals associated with the intermediate phase diminished, indicating that the intermediate phase was also completely converts to the crystalline perovskite phase upon thermal annealing. Also, diffraction signals were analogous to the phase composition of the reference sample while VRH O/DMF value 2

was less than 0.7%. However, for sample with VRH O/DMF=0.7%, the inexistence of other impurity 2

phases independent of perovskite are observed. With respect to the sample with VRH O/DMF=0.9%, 2

residual PbI2 composition was highlighted due to the degradation of CH3NH3PbI3-xClx. As a consequence, it was assumed that there was no large influence of suitable H2O additive on the



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

phase purity of the remnant CH3NH3PbI3-xClx films. Based on the above observations, the underlying mechanism of perovskite formation in our system was proposed. For the as-cast perovskite thin film, the solvent still remained and intermediate phase precipitated as the solvent slowly evaporated. After thermal annealing, the intermediate phase in original films volatilized resulting in the fully formation of crystalline perovskite. However, compared to the reference sample, H2O was added in situ during spin-coating. And H2O rich regions were chiefly located in the grain boundary of films according to the previous reports.12 Due to the strong hydroscopic nature of CH3NH3I+ (MA+), it could occur that the diffusion of ions in as-cast film accumulated toward grain boundary, and thereby merging adjacent grains together. On the other hands, the additive of H2O may lead to the formation CH3NH3PbI3-xClx H2O, a monohydrate phase during the process of spin-coating.37 And the ●

monohydrate phase would recrystallize and fully transform the perovskite phase after thermal annealing. Obviously, this process needed additional time to remove H2O molecule, which made the recrystallization process quickly quench. These two effects could effectively control the crystallization rate of CH3NH3PbI3-xClx film, yielding uniform and densely-packed highly crystalline perovskite grains. The detailed crystallization distinction between CH3NH3PbI3-xClx films with and without H2O was proposed in Figure 8. It seemed that the moisture was one of the key components for preparing high quality, thick CH3NH3PbI3-xClx films. Although a universal challenge had been disclosed that moisture conditions caused a fatal influence on the crystallization and stability of perovskite materials,38,39 a fact that incorporating suitable water additives into the perovskite precursor solution indeed leaded to an improved CH3NH3PbI3-xClx perovskite quality was demonstrated.


Page 16 of 24

Page 17 of 24

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


Figure 9. (a) F-PSCs based on VRH O/DMF=0.5% stability measurement stored in air in dark as a function of storing time; (b) Corresponding power conversion efficiency of F-PSCs versus bending curvature. 2

Finally, we further tested the optimal F-PSCs concerning their stability against stored time and bending deformation. As shown in Figure 9a, the stability of controlled F-PSCs stored in ambient atmosphere was recorded by measuring the device under illumination with 35% humidity and without encapsulation. The traced cell showed good durability over 7 days, suggesting that the devices stored in the dark at room temperature were relatively stable, with a PCE drop of only 50% for 1 week. Additionally, it was also demonstrated that maintaining >90% of its original efficiency was received after maximal bending deformation (shown in Figure 9b). It did not suffer from cracking and shut down the cells’ performance at higher bending (20mm bending curvature), implying that PET provided higher flexibility during high bending. Moreover, when bending the F-PSCs exceeded 50 times, its efficiency still could still reach a considerable value that maintaining >85% of its original efficiency. All those findings suggested that F-PSCs based on VRH O/DMF=0.5% displayed an excellent stability. 2

█

CONCLUSION In this work, we optimize the CH3NH3PbI3-xClx during the spin-coating of a perovskite

precursor solution utilizing H2O additive. It is demonstrate that H2O-assisted perovskite deposition has critical influence on transformation pathway via its effect on merging grain boundary of the



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

pre-deposited film and putting off the recrystallization rate of intermediate phase. Specifically, the F-PSCs utilizing VRH O/DMF=0.5% yields a promising PCE over 13% with higher Jsc and FF. Our 2

results provide a promising route for high-efficient F-PSCs fabrication. █

ASSOCIATED CONTENT

Supporting information The Hall measurement for PET/ITO and Glass/ITO substrates. SEM images of the CH3NH3PbI3-xClx film prepared on PET/ITO substrate and Glass/ITO substrate, respectively. AFM images of the PET/ITO and Glass/ITO substrates.

Notes The authors declare no competing financial interest. █

ACKNOWLEDGEMENTS We appreciate financial support from the National Natural Science Foundation of China (Grant

No. 61504068) and Natural Science Foundation of Tianjin (Grant No. 16JCYBJC16800). █

REFERENCES

(1) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. Solvent Engineering for High-Performance Inorganic-Organic Hybrid Perovskite Solar Cells. Nat. Mater., 2014, 13, 897-903. (2) Lin, Q.; Armin, A.; Nagril, R. C. R.; Burn, P. L.; Meredith, P. Electro-Optical of Perovskite Solar Cells. Nature Photonics, 2015, 9,106-112. (3) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T. B.; Duan, H. S.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science, 2014, 345, 542-546. (4) Quarti, C.; Mosconi, E.; Ball, J. M.; D’lnnocenzo, V.; Tao, C.; Pathak, S.; Snaith, H. J.; Petrozza, A.; Angelis, F. D. Structural and Optical Properties of Methylammonium Lead


Page 18 of 24

Page 19 of 24

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


Iodide Across the Tetragonal to Cubic Phase Transition: Implications for Perovskite Solar Cells. Energy Environ. Sci., 2016, 9, 155-163. (5) Du, Y. Y.; Cai, H.; Wu, Y.; Xing, Z.; Li, Z.; Xu, J.; Huang, L.; Ni, J.; Li, J.; Zhang, J. Enhanced Planar Perovskite Solar Cells With Efficiency Exceeding 16% via Reducing the Oxygen Vacancy Defect State in Titanium Oxide Electrode. Phys. Chem. Chem. Phys., DOl: 10. 1039/C7CP01936J. (6) Du, Y. Y.; Cai, H.; Wen, H.; Wu, Y.; Huang, L.; Ni, J.; Li, J. Zhang, J. Novel Combination of Efficient Perovskite Solar Cells with Low Temperature Processed Compact TiO2 Layer via Anodic Oxidation. ACS Appl. Mater. Interfaces, 2016, 8, 12836-12842. (7) Guo, N.; Zhang, T.; Li, G.; Xu, F.; Qian, X.; Zhao, Y. A Simple Fabrication of CH3NH3PbI3 Perovskite for Solar Cells Using Low-purity PbI2. J. Semicond., 2017, 38, 014004. (8) Kojima A, Teshima K, Shirai Y, Miyasaka T, Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells, J. Am. Chem. Soc., 2009, 131 (17): 6050– 6051. (9) Tan, H.; Jain, A.; Voznyy, O.; Lan, X.; Arquer, F. P. G.; Fan, J. Z.; Quintero-Bermudez, R.; Yuan, M.; Zhang, B.; Zhao, Y.; Fan, F.; Li, P.; Quan, L. N.; Zhao, Y.; Lu, Z.; Yang, Z.; Hoogland, S.; Sargent, E. H. Efficient and Stable Solution-Processed Planar Perovskite Solar Cells via Contact Passivation. Science, 2017, 355, 722-726. (10) W. S. Yang, B. W. Park, E. H. Jung, N. J. Jeon, Y. C. Kim, D. U. Lee, S. S. Shin, J. Seo, E. K. Kim, J. H. Noh, S. Seok. Iodide management in formamidinium-lead-halide-based perovskite layers for efficient solar cells. Science 356 (2017) 1376-1379. (11) Du, Y. Y.; Cai, H.; Ni, J.; Li, J.; Yu, H.; Sun, X.; Wu, Y.; Wen, H.; Zhang, J. Air-Processed,



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

Efficient CH3NH3PbI3-xClx Perovskite Solar Cells with Organic Polymer PTB7 as a Hole-transport Layer. RSC Adv., 2015, 5, 66981-66987. (12) Chiang, C. H.; Nazeeruddin, M. K.; Gratzel, M.; Wu, C. G. The Synergistic Effect of H2O and DMF Towards Stable and 20% Efficiency Inverted Perovskite Solar Cells. Energy Environ. Sci., 2017, 10, 808-817. (13) Rong, Y.; Tang, Z.; Zhao, Y.; Zhong, X.; Venkatesan, S.; Graham, H.; Patton, M.; Jing, Y.; Guloy, A. M.; Yao, Y. Solvent Engineering Towards Controlled Grain Growth in Perovskite Planar Heterojunction Solar Cells. Nanoscale, 2015, 7, 10595-10599. (14) Li, X.; Bi, D.; Yi, C.; Decoppet, J. D.; Luo, J.; Zakeeruddin, S. M.; Hagfeldt, A.; Gratzel, M. A vacuum Flash-Assisted Solution Process for High-efficiency Large-area Perovskite Solar Cells. Science, 2016, 353, 58-62. (15) Gonzalez-Pedro, V.; Juare-Perez, E. J.; Arsyad, W.; Barea, E. M.; Fabregat-Santiago, F.; Mora-Sero, I.; Bisquert, J. General Working Principles of CH3NN3PbX3 Perovskite Solar Cells. Nano Lett., 2014, 14, 888-893. (16) Xu, F.; Zhang, T.; Li, G.; Zhao, Y. Synergetic Effect of Chloride Doping and CH3NH3PbCl3 on CH3NH3PbI3-xClx Perovskite-Based Solar Cells. ChemSusChem., 2017, 10, 2365-2369. (17) Li, Y.; Zhang, T.; Xu, F.; Wang, Y.; Li, G.; Yang, Y.; Zhao, Y. CH3NH3Cl Assisted Solvent Engineering for Highly Crystallized and Large Grain Size Mixed-Composition (FAPbI3)0.85(MAPbBr3)0.15 Perovskites. Crystals, 2017, 7, 272. (18) You, J.; Hong, Z.; Yang, M.; Chen, Q.; Cai, M.; Song, T. B.; Chen, C. C.; Lu, S.; Liu, Y.; Zhou, H.; Yang, Y. Low-Temperature Solution-Processed Perovskite Solar Cells with High Efficiency and Flexibility. ACS Nano. 2014, 8, 1674-1680.


Page 20 of 24

Page 21 of 24

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


(19) Roldan-Carmona, C.; Malinkiewicz, O.; Soriano, A.; Espallargas, G. M.; Garcia, A.; Reinecke, P.; Kroyer, T.; Dar, M. I.; Nazeeruddin, M. K.; Bolink, H. J. Flexible High Efficiency Perovskite Solar Cells. Energy Environ. Sci., 2014, 7, 994. (20) Chen, Y.; Chen, T.; Dai, L. Layer-by-Layer Growth of CH3NH3PbI3-xClx for Highly Efficient Planar Heterojunction Perovskite Solar Cells. Adv. Mater., 2015, 27, 1053-1059. (21) Liu, X.; Chueh, C. C.; Zhu, Z.; Jo, S. B.; Sun, Y.; Jen, A. K. Y. Highly Crystalline Zn2SnO4 Nanoparticles as Efficient Electron-Transporting Layers Toward Stable Inverted and Flexible Conventional Perovskite Solar Cells. J. Mater. Chem. A, 2016, 4, 15294-15301. (22) Ha, J.; Kim, H.; Lee, H.; Lim, K. G.; Lee, T. W.; Yoo, S. Device Architecture for Efficient, Low-hysteresis Flexible Perovskite Solar Cells: Replacing TiO2 with C60 Assisted by Polyethylenimine Ethoxylated Interfacial Layers. Solar Energy Material & Solar Cells., 2017, 161, 338-346. (23) Nejand, B. A.; Nazari, P.; Gharibzadeh, S.; Ahmadi, V.; Moshaii, A. All-Inorganic Large-Area Low-Cost and Durable Flexible Perovskite Solar Cells Using Copper Foil as a Substrate. Chem. Commun., 2017, 53, 747. (24) Yoon, J.; Sung, H.; Lee, G.; Cho, W.; Ahn, N.; Jung, H. S.; Choi, M. Superflexible, High-efficiency Perovskite Solar Cells Utilizing Graphene Electrodes: Towards Future Foldable Power Sources. Energy Environ. Sci., 2017, 10, 337-345. (25) Li, Y.; Meng, L.; Yang, Y.; Xu, G.; Hong, Z.; Chen, Q.; You, J.; Li, G.; Yang, Y.; Li, Y. High-efficiency Robust Perovskite Solar Cells on Ultrathin Flexible Substrates. Nat Commun., 2016, 7, 10214. (26) Du, Y. Y.; Cai, H.; Wen, H.; Wu, Y.; Li, Z.; Xu, J.; Huang, L.; Ni, J.; Li, J.; Zhang, J.



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

Revealing the Unfavorable Role of Superfluous CH3NH3PbI3 Grain Boundary Traps in Perovskite Solar Cells on Carrier Collection. RSC Adv., 2016, 6, 83264. (27) Bi, D.; Tress, W.; Dar, M. I.; Gao, P.; Luo, J.; Renevier, C.; Schenk, K.; Abate, A.; Giordano, F.; Baena, J. P. C.; Decoppet, J. D.; Zakeeruddin, S. M.; Nazeeruddin, M. K.; Gratzel, M.; Hagfeldt, A. Efficient Luminescent Solar Cells Based on Tailored Mixed-Cation Perovskite. Science, 2016, 2, e1501170. (28) Shao, Y.; Xiao, Z.; Bi, C.; Yuan, Y.; Huang, J. Origin and Elimination of Photocurrent Hysteresis by Fullerene Passivation in CH3NH3PbI3 Planar Heterojunction Solar Cell. Nat. Commun., 2014, 5, 5784. (29) Liang, P. W.; Liao, C. Y.; Chueh, C. C.; Zuo, F.; Williams, S. T.; Xin, X. K.; Lin, J.; Jen, A. K. Additive Enhanced Crystallization of Solution-Processed Perovskite for Highly Efficient Planar-Heterojunction Solar Cell. Adv. Mater., 2014, 26, 3748-3754. (30) Zuo, C.; Ding, L. An 80.11% FF record achieved for perovskite solar cells by using the NH4Cl additive. Nanoscale, 2014, 6, 9935-9938. (31) Qin, C.; Matsushima, T.; Fujihara, T.; Adachi, C. Multifunctional Benzoquinone Additive for Efficient and Stable Planar Perovskite Solar Cells. Adv. Mater., 2017, 29. (32) You, J.; Yang, Y.; Hong, Z.; Song, T. B.; Meng, L.; Liu, Y.; Jiang, C.; Zhou, H.; Chang, W. H.; Li, G.; Yang, Y. Moisture Assisted Perovskite Film Growth For High Performance Solar Cells. Appl Phys Lett., 2014, 105, 183902. (33) Liu, Z.; Shi, T.; Tang, Z.; Sun, B.; Liao, G. Using a Low-temperature Carbon Electrode for Preparing Hole-Conductor-Free Perovskite Heterojunction Solar Cells Under High Relative Humidity. Nanoscale, 2016, 8, 7017.


Page 22 of 24

Page 23 of 24

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


(34) Song, Z.; Abate, A.; Watthage, S.C.; Liyanage, G. K.; Phillips, A. B.; Steiner, U.; Graetzel, M.; Heben, M. J. Perovskite Solar Cells Stability in Humid Air: Partially Reversible Phase Transitions in the PbI2-CH3NH3I-H2O System. Adv. Energy Mater. 2016, 6, 1600846. (35) Chen, H. W.; Sakai, N.; Ikegami, M.; Miyaska, T. Emergence of Hysteresis and Transient Ferroelectric Response in Organo-Lead Halide Perovskite Solar Cells. J. Phys. Chem. Lett., 2015, 6, 164-169. (36) Wu, C. G.; Chiang, C. H.; Tseng, Z. L.; Nazeeruddin, M. K.; Hagfeldt, A.; Gratzel, M. High Efficiency Stable Inverted Perovskite Solar Cells Without Current Hysteresis. Energy Environ. Sci., 2015, 8, 2725-2733. (37) Yang, J.; Siempelkamp, B. D.; Liu, D.; Kelly, T. L. Investigation of CH3NH3PbI3 Degradation Rates and Mechanisms in Controlled Humidity Environments Using in Situ Techniques. ACS Nano, 2015, 9, 1955-1963. (38) Christians, J. A.; Herrera, P. A. M.; Kamat, P. V. Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite upon Controlled Exposure to Humidified Air. J. Am. Chem. Soc., 2015, 137, 1530-1538. (39) Wozny, S.; Yang, M.; Nardes, A. M.; Mercado, C. C.; Ferrere, S.; Reese, M. O.; Zhou, W.; Zhu, K. Controlled Humidity Study on the Formation of Higher Efficiency Formamidinium Lead Triiodide-Based Solar Cells. Chem. Mater., 2015, 27, 4814-4820.



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

Table Of Contents (TOC) graphic：：

Synopsis: The enhanced stability and efficiency of F-PSCs are achieved by incorporating controlled H2O additive into perovskite precursor solution.


Page 24 of 24

Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13

Recommend Documents