Hydrophobic Polystyrene Passivation Layer for Simultaneously

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A Hydrophobic Polystyrene Passivation Layer for Simultaneously Improved Efficiency and Stability in Perovskite Solar Cells Minghua Li, Xiaoqin Yan, Zhuo Kang, Yahuan Huan, Yong Li, Ruxiao Zhang, and Yue Zhang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b04776 • Publication Date (Web): 11 May 2018 Downloaded from http://pubs.acs.org on May 13, 2018

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ACS Applied Materials & Interfaces

A Hydrophobic Polystyrene Passivation Layer for Simultaneously Improved Efficiency and Stability in Perovskite Solar Cells Minghua Li,a Xiaoqin Yan,*a Zhuo Kang,a Yahuan Huan,a Yong Li,a Ruxiao Zhanga and Yue Zhang*ab

M. Li, Prof. X. Yan, Z. Kang, Y. Huan, Y. Li, R. Zhang, Prof. Y. Zhang

State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

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

Prof. Y. Zhang

Beijing Municipal Key Laboratory of New Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, China

KEYWORDS: Polystyrene layer, interface, nonradiative recombination, carrier transfer, perovskite solar cells

1

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ABSTRACT

The major restraint for the commercialization of the high-performance hybrid metal halide perovskite solar cells is the long-term stability, especially at the infirm interface between the perovskite film and organic charge transfer layer. Recently, engineering the interface between the perovskite and spiro-OMeTAD becomes an effective strategy to simultaneously improve the efficiency and stability in the perovskite solar cells. In this work, we demonstrated that introducing an interfacial polystyrene layer between the perovskite film and spiro-OMeTAD layer can effectively improve the perovskite solar cells photovoltaic performance. The inserted polystyrene layer can passivate the interface traps and defects effectively and decrease the nonradiative recombination, leading to enhanced photoluminescence intensity and carrier lifetime, without compromising the carrier extraction and transfer. Under the optimized condition, the perovskite solar cells with the polystyrene layer achieve an enhanced average power efficiency of about 19.61% (20.46% of the best efficiency) from about 17.63% with negligible current density-voltage hysteresis. Moreover, the optimized perovskite solar cells with the hydrophobic polystyrene layer can maintain about 85% initial efficiency after two months storage in open air conditions without encapsulation.

1. Introduction Solar energy is known as the most promising energy resource on account of its potential of cleanness and renewability. Recently, there is an unprecedented rise about the new generation thin-film photovoltaic devices based on the magic hybrid metal 2


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halide perovskite materials, which have high absorption coefficients, long carrier diffusion length, and tunable band gaps.1-5 The hybrid metal halide perovskite materials are generally based on the formula of ABX3, where A is usually Rb+, Cs+, methylammonium (MA+) and formamidinium (FA+), B is the divalent metal (such as Pb2+ and Sn2+), and X is the halide element of Cl-, Br-, I-, respectively.6-8 Recently, the power conversion efficiency (PCE) of perovskite solar cells have boosted rapidly to over 22 % since 3.8 % at 2009, which exhibits strong competitiveness compared with the commercial photovoltaic technologies based on the inorganic materials, such as Si, CuInGaSe and GaAs.8-24 Many works have been reported and implemented to bring the perovskite photovoltaic from the lab to the market.25-30 However, the commercialization transformation was limited by a lot of factors, such as the toxic of lead, hysteresis behavior, device long-term stability, and the cost efficiency. At present, the high-efficiency perovskite solar cells are usually prepared based on the organic hole transporting materials (HTM), such as spiro-OMeTAD and PTAA, which need additives or dopants to enhance the electronic properties. However, it has been reported that the additives of lithium salts and 4-tert-butyl pyridine can cause intensive degradation of the perovskite materials due to the hydrophilic properties. To address this problem, some metal oxide materials, such as Al2O3, ZnO, TiO2 and ZrO2, were deposited on the perovskite materials to enhance the device performance by decreasing the interface recombination and preventing the moisture infiltration.30-34 The hydrophobic carbon nanotubes were introduced to manipulate the interface of perovskite film and spiro-OMeTAD layer, which results in less hysteresis and better stability.35-37 The Han’s group deposited a thick carbon electrode substituting the organic HTM, such as spiro-OMeTAD or PTAA, to collect the photogenerated holes and improve the device stability extremely.38-39 And other groups have demonstrated to synthesize the dopant-free hole transporting materials, in which the hydrophilic additives are removed or avoided, to separate and transfer photogenerated carrier, which results in enhanced device stability.40-42 Therefore, engineering the interface between the perovskite film and organic charge transfer layers become an effective 3



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strategy and future development to improve the perovskite solar cells stability without compromising device efficiency. In this work, we deposited an interfacial polystyrene layer between the perovskite film and spiro-OMeTAD layer to improve the perovskite solar cells efficiency and stability. The fabricated perovskite solar cells with the polystyrene layer achieve an enhanced average power conversion efficiency of 19.61% (20.46% of the best efficiency) from 17.63%, and with a negligible hysteresis. The mechanism of carrier transfer and trap-assisted recombination process are systematically investigated and characterized by steady-state and time-resolved photoluminescence and impedance spectroscopy measurements. It’s found that the polystyrene layer can passivate the traps and defects at the interface of perovskite film and spiro-OMeTAD layer and decrease the subsequent nonradiative recombination, which is responsible for the enhanced photoluminescence intensity and carrier lifetime. The reduced electronic traps induce decreased interface capacitance and enhanced build-in potential, suggesting a rapid charge separation and transfer and less carrier accumulation at the interface, which is beneficial for the suppressive hysteresis behavior. Moreover, the unencapsulated perovskite solar cells with the hydrophobic polystyrene layer present the enhanced stability of maintaining about 85% initial efficiency in contrast to 65% initial efficiency of the control device after two months storage in the ambient conditions. 2. Results and discussion

In this work, the perovskite solar cells were fabricated as a normal structure of FTO/compact-TiO2

(40

nm,

with

YCl3

treatment)/mesoporous-TiO2

(150

nm)/perovskite (450 nm)/polystyrene layer/spiro-OMeTAD (200 nm)/Ag (120 nm). Figure 1a illustrates the schematic device structure (left) and the corresponding cross-sectional SEM image (right), in which cp-TiO2 and mp-TiO2 represent the 4


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compact TiO2 layer and mesoporous TiO2 layer, respectively. The CsFAMA-based Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3

is

adopted

as

the

standard

perovskite

composition, which is confirmed as an efficient perovskite absorber. The insulating polystyrene layer (chemical formula in Figure 1b) is employed as an interfacial layer between the perovskite film and hole transporting layer of spiro-OMeTAD layer, by depositing a series concentration of polystyrene solutions in dichlorobenzene. According to the previous reports on the energy levels of different functional layers, the schematic device diagram of energy levels was further depicted in Figure 1c. With the polystyrene layer, the photogenerated holes at valence band maximum (VBM) of perovskite film can transfer to the highest occupied molecular orbital (HOMO) of spiro-OMeTAD layer by tunnel effect. On the contrary, the polystyrene layer will block the photogenerated electrons transfer to HTM layer effectively due to no energy band matching, resulting in significant combination loss at the contact of perovskite film and spiro-OMeTAD layer. Moreover, the contact angle tests were performed in Figure 1d to evaluate the wettability of the perovskite film with and without polystyrene layer. With 10 mg/ml polystyrene layer, there is a hydrophobic surface formed with an increased contact angle of about 92.5o compared with 75.1o of the pristine perovskite film, which has a beneficial effect to protect the perovskite absorber layer, due to blocking the moisture infiltration into the perovskite film from the ambient environment.

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Figure 1. (a) Schematic device structure of the perovskite solar cell (left) and the cross-sectional SEM image of the completed device (right), (b) schematic chemical formula of the polystyrene, (c) the corresponding schematic energy level diagram of perovskite film and different functional layers, and (d) contact angle tests of the perovskite films without (top) and with (down) polystyrene layer, respectively.

The characterizations of the perovskite films were performed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and UV-vis absorption spectra. In Figure S1, there is no distinct difference observed for the two uniform and pinhole-free perovskite films before the polystyrene layer coating. The XRD patterns (in Figure S2a) of the two perovskite films show similar crystallinity with a small PbI2 peak at 12.6o, in which the trace of residual PbI2 phase can passivate the defects at grain boundaries and is favorable for the device performance.43-45 In addition, the two perovskite films present almost identical UV-vis absorption spectra (see Figure S2b in supporting information) with high absorption in the measured wavelength range. As a 6


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result, it can reach a conclusion that no significant difference was observed between the two perovskite films before the interfacial layer coating, and the influences from the difference of perovskite films on the device photovoltaic performance can be ruled out.

Then, a series concentration of polystyrene layers was successfully deposited on the perovskite films, and the photographic image was captured in Figure S3. All the perovskite films exhibit similar appearance with smooth and uniform surface. The perovskite films with low concentration of polystyrene layers (< 10 mg/ml) present black surface. With polystyrene concentration further increase, the surface color gets dark yellow gradually. In Figure 2a, the SEM image shows distinct grain boundary for the pristine perovskite film. While, with polystyrene layers deposition, the grain boundary changes to be ambiguous gradually. This might come from the weak conductivity of polystyrene layer. The atomic force microscopy (AFM) in Figure 2b was additionally employed to characterize the topography of the perovskite films with different concentration of polystyrene layers. The root mean square roughness (RMS) values of the perovskite films (summarized in Table S1) decrease from 17.4 nm to 8.5 nm along with the polystyrene concentration augment, which leads to a more uniform and flat interface between the perovskite film and spiro-OMeTAD layer.

Steady-state and time-resolved photoluminescence (PL) measurements were further performed in Figure 2c and 2d to investigate the photo-physical properties and recombination behavior of perovskite films with different concentration of 7



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polystyrene layers.46-47 When the perovskite films with different concentration of polystyrene layers were deposited on glasses, a significant PL intensity increase (in Table S2) is observed for the perovskite film with 10 mg/ml polystyrene layer compared with the pristine perovskite film, which suggests a suppressive nonradiative recombination process of electron-hole pairs. Increasing the polystyrene concentration continuously, the PL intensities drop gradually. This is due that the thicker polystyrene layers induce severe nonradiative recombination. In order to confirm the carrier lifetime accurately, the time-resolved PL spectra of perovskite films are analyzed and fitted as the biexponential function: PLintensity= A1exp(-t/τ1) + A2exp(-t/τ2), and the detailed results are summarized in Table S3. According to previous reports, the fast decay (τ1) is related to bimolecular recombination of photogenerated carriers, and the slow decay (τ2) is mainly attributed to the trap-assisted carrier recombination.22 For the pristine perovskite film, the fitted results are τ1 = 29.71 ns with 21.55 % percentage, and τ2 = 284.79 ns with 78.45 % percentage, respectively. When with the 10 mg/ml polystyrene layer, the slow decay (τ2) enhances to 468.76 ns with 93.86 % percentage, indicating a prolonged slow recombination process due to the decreased nonradiative recombination. Thus, a longer carrier lifetime of 441.51 ns is obtained for the perovskite film with 10 mg/ml polystyrene layer in contrast to 229.83 ns of the pristine perovskite film, which is consistent with the steady-state PL results. Subsequently, the spiro-OMeTAD hole transporting layers were deposited on all the perovskite films to study the carrier transfer between the perovskite films and the charge transfer layers. It’s found that a significant PL density quenching (see Table S2) 8


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is observed for the perovskite film with 10 mg/ml polystyrene layer compared with the pristine perovskite film, suggesting that an effective carrier transfer from perovskite film to HTM layer. As the summarized results in Table S3, the pristine perovskite film has a decay time of 14.07 ns, which includes a fast decay (τ1) of 10.22 ns with 97.64 % percentage and a slow decay (τ2) of 173.42 ns with 2.36 % percentage, respectively. After depositing 10 mg/ml polystyrene layer, the percentage of the fast decay process enhances to about 98.54% to dominate the whole decay process. And both τ1 and τ2 decrease to 7.59 ns and 137.78 ns, respectively, leading to a reduced carrier lifetime of 9.49 ns. This indicates a high-efficiency carrier transfer and extraction from the perovskite film to the HTM layer. Therefore, it can be concluded that the polystyrene layer can combine two aspects of functions, including passivating nonradiative recombination and facilitating carrier transfer, which is a suitable candidate as interfacial modifier.

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Figure 2. Properties of the perovskite film with different concentration of polystyrene layers. (a) Top-view SEM images, (b) topographical images, (c) steady-state photoluminescence spectra, and (d) time-resolved photoluminescence spectra, respectively. The perovskite film without polystyrene layer is labeled as pristine, and the perovskite films with different concentration of polystyrene layers are labeled as 1 mg/ml, 5 mg/ml, 10 mg/ml, 15 mg/ml and 20 mg/ml, respectively.

Then, the normal mesoporous perovskite solar cells (as shown in Figure 1a) were fabricated and tested to explore the device photovoltage performance evolution along with the polystyrene concentration. In Figure 3a, the typical current density-voltage (J-V) curves were shown for the perovskite solar cells with different concentration of polystyrene layers. And the statistic results of detailed photovoltaic parameters are plotted and summarized in Figure 3b-c and Table S4. With the polystyrene concentration increasing from 0 to 10 mg/ml, the values of open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) augment from 1.136 to 1.152 V, 21.24 to 21.99 mA cm-2, 0.731 to 0.774 and 17.63 to 19.61%, respectively, which might come from good defect passivation and excellent carrier transfer. Increasing the polystyrene concentration further, the PCE drops to 18.29%, including decreased Jsc and FF of 21.53 mA cm-2 and 0.748, which is mainly due that the increased insulativity of thicker polystyrene layer impedes the carrier transfer from perovskite film to HTM. Under the optimized experimental condition, the J-V curves (in Figure 3d and Table 1) of the best perovskite solar cells with and without polystyrene layers are measured at different scan directions to study 10


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the

device

hysteresis

behavior.

The

hysteresis

index

of

h=(PCEreverse-PCEforward)/PCEreverse was introduced to evaluate the hysteresis quantitatively. A small hysteresis index of about 1.2% was obtained for the perovskite solar cell with interfacial polystyrene layer compared with about 15% for the pristine perovskite solar cell. This suppressive hysteresis behavior might result from enhanced carrier transfer and decreased interface capacitance. External quantum efficiency (EQE) spectra were further carried out and plotted in Figure 3e to confirm the enhanced Jsc. The perovskite solar cell with polystyrene layer exhibits a higher integrated Jsc of 22.16 mA cm-2 than 21.82 mA cm-2 of the control device, which have little discrepancy with the former results of J-V curves. The increased EQE at the long wavelength from about 680 nm to 780 nm is assigned to the reduced nonradiative recombination due to the traps passivation. Figure 3f presents the steady-state power output over time of the two perovskite solar cells. There is a higher steady-state power output of about 20.08% obtained for the perovskite solar cell with polystyrene layer, which exhibits a stable and continuous power output without Jsc decline over time. However, a significant Jsc decline from 19.27 mA cm-2 to 18.31 mA cm-2 over 200 s was observed for the control perovskite solar cell, which results in a lower steady-state efficiency of about 17.30%. Therefore, it comes to a conclusion that the performance of perovskite solar cells can be improved successfully by inserting an interfacial modifier of polystyrene layer between perovskite film and HTM layer.

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Figure 3. Effects of different concentration of polystyrene layers on the photovoltaic performance of the perovskite solar cells. (a) J-V curves, (b) and (c) statistic results of detailed performance parameters measured at reverse scan. The photovoltaic performance of best perovskite solar cells with and without polystyrene layer, (d) J-V curves measured at reverse and forward scan, (e) EQE spectra and integrated Jsc values, and (f) steady-state measurements of Jsc and PCE, respectively.

Table 1. Photovoltaic parameters of the best perovskite solar cells with and without polystyrene layer. Sample

Scan direction

Voc (V)

Jsc (mA cm-2)

FF

PCE (%)

RS

1.139

21.86

0.773

19.24

FS

1.068

21.86

0.700

16.35

RS

1.158

22.32

0.792

20.46

FS

1.151

22.32

0.787

20.22

Pristine

Steady-state PCE (%)

17.30

Polystyrene

20.08

In order to study the charge transfer and recombination mechanism of the perovskite solar cells, impedance spectroscopy measurements were carried out and 12


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analyzed systemically. In Figure 4a, two typical Nyquist plots of the perovskite devices with and without polystyrene layer were measured at 0.6 V bias under illumination. There are two obvious semicircles observed for all the Nyquist plots in the measured frequency range. According to the previous reports, an equivalent circuit with resistance (R) and resistance-capacitance (R-C) components was introduced, as shown in the inset of Figure 4a, to fit the obtained Nyquist plots.47-49 The first semicircle in the high-frequency range is attributed to the charge transfer and recombination between the perovskite film and charge transfer layers, and the low-frequency semicircle is mainly related to slow ion relaxation and diffusion process in the perovskite film. Figure 4b shows the obtained series resistance (Rs) values of two perovskite solar cells at different applied bias under illumination, which are determined by the intercept of the Nyquist plot and x-axis in the high-frequency range. The perovskite solar cell with polystyrene layer exhibits lower Rs values than the control device at the same bias condition, which is responsible for the increased Jsc and FF due to efficient charge transfer and extraction. While the recombination resistance (Rrec) values (in Figure 4c) are higher for the perovskite solar cell with polystyrene layer than that of the pristine perovskite device, suggesting less charge recombination loss between the perovskite film and HTM layer.

In the capacitance-frequency (C-f) plots of Figure 4d, the perovskite solar cell with polystyrene layer presents decreased capacitance compared with that of pristine perovskite solar cell in the measured frequency from 1 MHz to 1 Hz, which has favorable effect on the decreased hysteresis behavior.31, 50-51 Figure 4e illustrates the 13



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Mott-Schottky plots of the two perovskite solar cells with and without polystyrene layer. The detailed information is analyzed and summarized in Table S5 by fitting the ଵ

equation:

஼మ

ଶ

= ௤ఌఌ

బ ே೏

(ܸ − ܸ௕௜ −

௞் ௤

) , where C is the capacitance; q, ε and ε0

represent the elementary charge, dielectric constant, and vacuum permittivity; and Nd, V, Vbi, k and T are the carrier density, applied bias, build-in potential, Boltzmann constant and absolute temperature, respectively.39, 52 With the polystyrene layer, the perovskite solar cell presents increased build-in potential (Vbi) of 0.916 V and decreased carrier density (Nd) of 1.58*1016 cm-3, which can provide enhanced driving force for photogenerated carrier transfer and result in less carrier accumulation at the interface, compared with 0.885 V and 1.94*1016 cm-3 of the pristine perovskite device. Then, the values of depletion width (W) can be calculated according to the equation:

ܹ=ට

ଶఌ(௏್೔ ି௏) ௤ே೏

. As a result, the perovskite solar cell with polystyrene layer has a

longer W of 384.78 nm than 341.23 nm of the control device, which is responsible for the Voc improvement. Combining with the results of C-f and Mott-Schottky plots, the values of trap density of states (tDOS) are calculated using the equation: ܰ୘ (‫ܧ‬ఠ ) =

−

௏ౘ౟ ௗ஼ ఠ

௤ௐ ௗఠ ௞்

, where Eω represents the energy demarcation, and ω is the angular

frequency, respectively.53-55 It has been reported that the shallow trap states are related to the traps at grain boundaries, and the deep trap states are mainly assigned to the defects at the film surface.22 By comparing the two tDOS spectra in Figure 4f, the two perovskite solar cells exhibit similar shallow trap states at lower energy region (below 0.43 eV), which is due that the two perovskite absorber layers present identical photovoltaic properties (discussed early). While the tDOS drops significantly over 14


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0.43 eV of Eω for the perovskite solar cell with the polystyrene layer, which is attributed to the passivated interface between the perovskite film and HTM layer by polystyrene layer, leading to better carrier transfer and consequent device performance. Thus, it can be understood that the polystyrene layer could passivate the traps and defects at the interface between the perovskite film and HTM layer, without infiltrating into the perovskite grain boundaries to reduce traps, which is different from the fullerene derivative, such as PCBM and IDIC.56-57 Therefore, it is feasible to conclude that the improved performance of the perovskite solar cells is assigned to the favorable interface passivation effect of the polystyrene layer, decreased interface capacitance and good carrier transfer.

Figure 4. Impedance spectroscopy measurements of the perovskite solar cells with and without polystyrene layers. (a) Nyquist plots measured at 0.6 V bias under light condition, (b) and (c) plots of series resistance (Rs) and recombination resistance (Rrec) at different applied bias, (d) frequency dependent capacitance (C-f) measurements, (e) 15



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Mott-Schottky plots, (f) calculated trap density of states (tDOS) plots, respectively. The inset shows the equivalent circuit of the Nyquist plots.

In addition, the device stability tests were also carried out to compare and assess the environmental resistance of perovskite solar cells with and without polystyrene layers. As shown in Figure 5 a-d, the perovskite solar cell with polystyrene layer maintains about 85% initial PCE after stored in the ambient conditions for two months without encapsulation. While the efficiency of the pristine perovskite solar cell drops to about 65% initial PCE after two months storage. This efficiency decline is mainly due to the significant loss of Jsc and FF, which might result from the perovskite film decomposition. In order to explore the origin of the improved device stability, the contact angle tests were conducted systemically in Figure S3. It can be found that all the polystyrene-modified perovskite films regardless with and without HTM layers exhibit higher contact angle than the control films, and the contact angle values drop along with time. The contact angle of the polystyrene-modified perovskite film (with spiro-OMeTAD layer) enhances to about 92.5o (94.6o) in contrast to about 75.1o (84.9o) of the pristine perovskite film (with spiro-OMeTAD layer). After 4 min, the contact angle decreases less of about 12.7o (8.1o) for the polystyrene-modified perovskite film (with spiro-OMeTAD layer) than 16.7o (10.4o) of the pure perovskite film (with spiro-OMeTAD layer), suggesting a better environmental resistance, which is beneficial for the enhanced device stability. Moreover, Figure S4 shows the real photographic image of the perovskite solar cells with and without polystyrene layers before and after two months storage in open air conditions. The two as-prepared 16


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perovskite solar cells present almost the same appearance on the both sides. After two months storage, the Ag electrode can be easily observed from the backside for the pristine perovskite solar cell, which means the perovskite absorber has been almost decomposed. As for the polystyrene-modified perovskite solar cell, it can be found that the device color is still black and opaque, and Ag electron can't be observed from backside view, which is attributed to the well protection from the polystyrene layer. Hence, it’s obvious that the polystyrene layer is a useful protection for the perovskite films due to the good hydrophobic properties.

Figure 5. Stability tests of the perovskite solar cells with and without polystyrene layers in ambient conditions without encapsulation. Plots of (a) Normalized PCE, (b) normalized Voc, (c) normalized Jsc, and (d) normalized FF, respectively.

3. Conclusion

In summary, the photovoltaic performance of the perovskite solar cells was improved successfully by depositing an interfacial polystyrene layer between the 17



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perovskite film and spiro-OMeTAD layer. The inserted polystyrene layer can enhance the photoluminescence intensity and carrier lifetime effectively by reducing the nonradiative recombination, and facilitates the carrier extraction and transfer due to the passivated traps and defects at the interface between the perovskite film and HTM layer. Under optimized experimental condition, the perovskite solar cells with polystyrene layer achieve a best efficiency of about 20.46% (20.22% at forward scan) and a steady-state power output of about 20.08%. With the polystyrene layer, the efficiency of perovskite solar cells maintains a higher initial efficiency of about 85% than 65% of the control device after two months storage in open air conditions, which is attributed to the good hydrophobic property of the polystyrene layer. Therefore, the introduction of polystyrene layer between the perovskite film and HTM layer provides a new and useful route to prepare high-efficiency and stable photovoltaic devices, even with other perovskite materials or device structures.

4. Experimental Section

Materials Preparation: Without specially noted, all chemicals were purchased from Sigma-Aldrich and used as received. The titanium butoxide (98%) was purchased from Aladdin. The YCl3 powder (99.9%) and diethanolamine (99%) were purchased from Alfa Aesar. FAI, MABr, PbI2 and PbBr2 were purchased from Xi’an Polymer Light Technology Corp.

Precursor preparation: The precursor of compact TiO2 layer was prepared by dissolving 0.25M titanium butoxide with 5 mol% YCl3 in ethanol with 2 vol% 18


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diethanolamine.58 The perovskite precursor was made by mixing 1.1 M PbI2, 1 M FAI, 0.22 M PbBr2, 0.2 M MABr and 50 ul CsI (1.5 M in DMSO) in anhydrous DMF: DMSO (4:1). The hole transporting layer solution was prepared by dissolving 72.3 mg spiro-OMeTAD, 17.5 ul bis(trifluoromethylsulfonyl)imide lithium (520 mg in 1 ml acetonitrile) and 28.8 ul 4-tert-butylpyridine. The polystyrene solution was prepared from 1 mg/ml to 20 mg/ml dissolved in dichlorobenzene.

Device Fabrication: The compact TiO2 layer was prepared by spin-coating the compact TiO2 precursor at 2500 rpm for 30 s on the precleaned FTO substrates. After drying at 125 oC for 5 min, the mesoporous TiO2 scaffold was spin coated using Dyesol 30NRD (150 mg/ml in ethanol) at 5000 rpm for 30 s, following by sintering at 500 oC for 30 min in the furnace. The perovskite precursor was spin coated on the prepared substrates at 1000 rpm and 6000 rpm for 10 s and 30 s, respectively, and 100 ul chlorobenzene was dropped at 10 s of the second spinning programme. After annealing at 100oC for 30 min, a thin polystyrene layer was deposited on the perovskite films by spinning coating at 4000 rpm for 30 s. Then, all the perovskite films with and without polystyrene layers were annealed at 100oC for another 30 min. The spiro-OMeTAD were deposited at 4000 rpm for 30 s. Finally, about 120 nm of Ag layer was thermal evaporated to complete the device. The device active area was 0.12 cm2.

Film and Device Characterization: The SEM images was investigated using a Field Emission Scanning Electron Microscope (FEI, Quanta 3D). The optical absorption 19



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spectra were measured by UV/vis spectrophotometer (Shimadzu, UV-3600). The XRD characteristic was measured by Rigaku DMAX-RB equipped with Cu-Kα X-ray radiation source. Steady-state photoluminescence spectra were measured using Horiba JY-HR800 with an excitation of 532 nm. The time-resolved photoluminescence spectra were measured at 765 nm by Edinburgh Instruments (FLS980) with an excitation of 470 nm. The photovoltaic curves were measured under simulated AM 1.5G irradiation (100 mW cm-2) using a Xenon-lamp solar simulator (Oriel, 911A). A Si-reference cell citified by NIST was used to calibrate the lamp light. The J-V curves and impedance spectroscopy were performed using an electrochemical work station (CHI 660E) in the ambient atmosphere. The impedance spectroscopy measurements were carried out under different applied bias at 20 mV perturbation between the range of 1 MHz to 1 Hz under light and dark condition. The energy demarcation (Eω) was determined by the angular frequency (ω) as the equation: Eω=kT•ln(ω0/ω), where ω0 represents the attempt-to-escape frequency. The EQE spectra were recorded by Stanford Research Systems model SR830 DSP lock-in amplifier coupled with WDG3 monochromator and 500 W xenon lamp. The contact angle measurements were performed using KRUSS (DSA 100). The perovskite solar cells were stored in the ambient conditions of about 30%- 50% humidity for two months to test the device stability.

ASSOCIATED CONTENT

Supporting Information. 20


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The following files are available free of charge.

The SEM images, XRD patterns and UV-vis absorption spectra survey spectra of the perovskite films, the contact angle tests, and the photographic image of the perovskite solar cells with and without polystyrene layers. Film roughness results, detailed parameters of the steady-state and time-resolved PL spectra, statistic performance parameters of the device with different concentration of polystyrene layers, and the fitting results of Mott-schottky plots.

AUTHOR INFORMATION

Corresponding Author

X. Yan, Email: [email protected]；[email protected] ACKNOWLEDGMENT This work was supported by National Natural Science Foundation of China (No. 51772024, 51372023 and 51702014), the National Key Research and Development Program of China (No. 2016YFA0202701), the National Major Research Program of China (No. 2013CB932601), the Program of Introducing Talents of Discipline to Universities (B14003), Beijing Municipal Science & Technology Commission, the Fundamental Research Funds for Central Universities. REFERENCES (1) Liu, M.; Johnston, M. B.; Snaith, H. J. Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395-398. (2) Kim, H.-S.; Im, S. H.; Park, N.-G. Organolead Halide Perovskite: New Horizons in Solar Cell Research. J. Phys. Chem. C 2014, 118, 5615-5625. (3) Park, N.-G. Organometal Perovskite Light Absorbers toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell. J. Phys. Chem. Lett. 2013, 4, 2423-2429. (4) Baikie, T.; Fang, Y.; Kadro, J. M.; Schreyer, M.; Wei, F.; Mhaisalkar, S. G.; Graetzel, M.; White, T. J. Synthesis and Crystal Chemistry of the Hybrid Perovskite (Ch3nh3)Pbi3 for Solid-State Sensitised Solar Cell Applications. J. Mater. Chem. A 21



Page 22 of 27

2013, 1, 5628-5641. (5) Bisquert, J. The Swift Surge of Perovskite Photovoltaics. J. Phys. Chem. Lett. 2013, 4, 2597-2598. (6) Eperon, G. E.; Stranks, S. D.; Menelaou, C.; Johnston, M. B.; Herz, L. M.; Snaith, H. J. Formamidinium Lead Trihalide: A Broadly Tunable Perovskite for Efficient Planar Heterojunction Solar Cells. Energy Environ. Sci. 2014, 7, 982-988. (7) Saliba, M.; Matsui, T.; Seo, J. Y.; Domanski, K.; Correa-Baena, J. P.; Nazeeruddin, M. K.; Zakeeruddin, S. M.; Tress, W.; Abate, A.; Hagfeldt, A.; Gratzel, M. Cesium-Containing Triple Cation Perovskite Solar Cells: Improved Stability, Reproducibility and High Efficiency. Energy Environ. Sci. 2016, 9, 1989-1997. (8) Saliba, M.; Matsui, T.; Domanski, K.; Seo, J. Y.; Ummadisingu, A.; Zakeeruddin, S. M.; Correa-Baena, J. P.; Tress, W. R.; Abate, A.; Hagfeldt, A. Incorporation of Rubidium Cations into Perovskite Solar Cells Improves Photovoltaic Performance. Science 2016, 354, 206. (9) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050-6051. (10) Kim, H.-S.; Lee, C.-R.; Im, J.-H.; Lee, K.-B.; Moehl, T.; Marchioro, A.; Moon, S.-J.; Humphry-Baker, R.; Yum, J.-H.; Moser, J. E.; Grätzel, M.; Park, N.-G. Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%. Sci. Rep. 2012, 2, 591-597. (11) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites. Science 2012, 338, 643-647. (12) Burschka, J.; Pellet, N.; Moon, S.-J.; Humphry-Baker, R.; Gao, P.; Nazeeruddin, M. K.; Gratzel, M. Sequential Deposition as a Route to High-Performance Perovskite-Sensitized Solar Cells. Nature 2013, 499, 316-319. (13) 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. Nat. Mater. 2014, 13, 897-903. (14) 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. (15) Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. Compositional Engineering of Perovskite Materials for High-Performance Solar Cells. Nature 2015, 517, 476-480. (16) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. High-Performance Photovoltaic Perovskite Layers Fabricated through Intramolecular Exchange. Science 2015, 348, 1234-1237. (17) Nie, W.; Tsai, H.; Asadpour, R.; Blancon, J.-C.; Neukirch, A. J.; Gupta, G.; Crochet, J. J.; Chhowalla, M.; Tretiak, S.; Alam, M. A.; Wang, H.-L.; Mohite, A. D. High-Efficiency Solution-Processed Perovskite Solar Cells with Millimeter-Scale Grains. Science 2015, 347, 522-525. (18) Bi, D.; Yi, C.; Luo, J.; Décoppet, J.-D.; Zhang, F.; Zakeeruddin, Shaik M.; Li, X.; 22


Page 23 of 27 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


Hagfeldt, A.; Grätzel, M. Polymer-Templated Nucleation and Crystal Growth of Perovskite Films for Solar Cells with Efficiency Greater Than 21%. Nature Energy 2016, 1, 16142. (19) Li, X.; Bi, D.; Yi, C.; Décoppet, J. D.; Luo, J.; Zakeeruddin, S. M.; Hagfeldt, A.; Grätzel, M. A Vacuum Flash-Assisted Solution Process for High-Efficiency Large-Area Perovskite Solar Cells. Science 2016, 353, 58. (20)Tan, H.; Jain, A.; Voznyy, O.; Lan, X.; Fp, G. D. A.; Fan, J. Z.; Quinterobermudez, R.; Yuan, M.; Zhang, B.; Zhao, Y. Efficient and Stable Solution-Processed Planar Perovskite Solar Cells Via Contact Passivation. Science 2017, 355, 722. (21) Chen, H.; Ye, F.; Tang, W.; He, J.; Yin, M.; Wang, Y.; Xie, F.; Bi, E.; Yang, X.; Grätzel, M.; Han, L. A Solvent- and Vacuum-Free Route to Large-Area Perovskite Films for Efficient Solar Modules. Nature 2017, 550, 92. (22) Zheng, X.; Chen, B.; Dai, J.; Fang, Y.; Bai, Y.; Lin, Y.; Wei, H.; Zeng, Xiao C.; Huang, J. Defect Passivation in Hybrid Perovskite Solar Cells Using Quaternary Ammonium Halide Anions And cations. Nature Energy 2017, 2, 17102. (23) Shin, S. S.; Yeom, E. J.; Yang, W. S.; Hur, S.; Kim, M. G.; Im, J.; Seo, J.; Noh, J. H.; Seok, S. I. Colloidally Prepared La-Doped Basno3 Electrodes for Efficient, Photostable Perovskite Solar Cells. Science 2017, 356, 167. (24) Yang, W. S.; Park, B.-W.; Jung, E. H.; Jeon, N. J.; Kim, Y. C.; Lee, D. U.; Shin, S. S.; Seo, J.; Kim, E. K.; Noh, J. H.; Seok, S. I. Iodide Management in Formamidinium-Lead-Halide–Based Perovskite Layers for Efficient Solar Cells. Science 2017, 356, 1376-1379. (25) Rong, Y.; Liu, L.; Mei, A.; Li, X.; Han, H. Beyond Efficiency: The Challenge of Stability in Mesoscopic Perovskite Solar Cells. Adv. Energy Mater. 2015, 5, 1501066. (26) Leijtens, T.; Eperon, G. E.; Noel, N. K.; Habisreutinger, S. N.; Petrozza, A.; Snaith, H. J. Stability of Metal Halide Perovskite Solar Cells. Adv. Energy Mater. 2015, 5, 1500963. (27) Stoumpos, C. C.; Kanatzidis, M. G. Halide Perovskites: Poor Man's High-Performance Semiconductors. Adv. Mater. 2016, 28, 5778-5793. (28) 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, 768-771. (29) Hou, Y.; Du, X.; Scheiner, S.; Mcmeekin, D. P.; Wang, Z.; Li, N.; Killian, M. S.; Chen, H.; Richter, M.; Levchuk, I. A Generic Interface to Reduce the Efficiency-Stability-Cost Gap of Perovskite Solar Cells. Science 2017, 358, 1192-1197. (30) Chen, W.; Wu, Y.; Yue, Y.; Liu, J.; Zhang, W.; Yang, X.; Chen, H.; Bi, E.; Ashraful, I.; Grätzel, M.; Han, L. Efficient and Stable Large-Area Perovskite Solar Cells with Inorganic Charge Extraction Layers. Science 2015, 350, 944-948. (31) Koushik, D.; Verhees, W. J. H.; Kuang, Y.; Veenstra, S.; Zhang, D.; Verheijen, M. A.; Creatore, M.; Schropp, R. E. I. High-Efficiency Humidity-Stable Planar Perovskite Solar Cells Based on Atomic Layer Architecture. Energy Environ. Sci. 2017, 10, 91-100. (32) You, J.; Meng, L.; Song, T. B.; Guo, T. F.; Yang, Y. M.; Chang, W. H.; Hong, Z.; 23



Page 24 of 27

Chen, H.; Zhou, H.; Chen, Q. Improved Air Stability of Perovskite Solar Cells Via Solution-Processed Metal Oxide Transport Layers. Nat. Nanotechnol. 2016, 11, 75-81. (33) Chen, W.; Xu, L.; Feng, X.; Jie, J.; He, Z. Metal Acetylacetonate Series in Interface Engineering for Full Low-Temperature-Processed, High-Performance, and Stable Planar Perovskite Solar Cells with Conversion Efficiency over 16% on 1 Cm2 Scale. Adv. Mater. 2017, 29, 1603923. (34) Yue, S.; Liu, K.; Xu, R.; Li, M.; Azam, M.; Ren, K.; Liu, J.; Sun, Y.; Wang, Z.; Cao, D.; Yan, X.; Qu, S.; Lei, Y.; Wang, Z. Efficacious Engineering on Charge Extraction for Realizing Highly Efficient Perovskite Solar Cells. Energy Environ. Sci. 2017, 10, 2570-2578. (35) Aitola, K.; Sveinbjörnsson, K.; Baena, J. P. C.; Kaskela, A.; Abate, A.; Tian, Y.; Johansson, E. M. J.; Grätzel, M.; Hagfeldt, A.; Boschloo, G. Carbon Nanotube-Based Hybrid Hole-Transporting Material and Selective Contact for High Efficiency Perovskite Solar Cells. Energy Environ. Sci. 2016, 9, 461-466. (36) Ihly, R.; Dowgiallo, A. M.; Yang, M.; Schulz, P.; Stanton, N.; Reid, O. G.; Ferguson, A.; Zhu, K.; Berry, J. J.; Blackburn, J. Efficient Charge Extraction and Slow Recombination in Organic-Inorganic Perovskites Capped with Semiconducting Single-Walled Carbon Nanotubes. Energy Environ. Sci. 2016, 9, 1439-1449. (37) Tiong, V. T.; Pham, N. D.; Wang, T.; Zhu, T.; Zhao, X.; Zhang, Y.; Shen, Q.; Bell, J.; Hu, L.; Dai, S.; Wang, H. Octadecylamine-Functionalized Single-Walled Carbon Nanotubes for Facilitating the Formation of a Monolithic Perovskite Layer and Stable Solar Cells. Adv. Funct. Mater. 28, 1705545. (38) Mei, A.; Li, X.; Liu, L.; Ku, Z.; Liu, T.; Rong, Y.; Xu, M.; Hu, M.; Chen, J.; Yang, Y.; Grätzel, M.; Han, H. A Hole-Conductor–Free, Fully Printable Mesoscopic Perovskite Solar Cell with High Stability. Science 2014, 345, 295-298. (39) Liu, L.; Mei, A.; Liu, T.; Jiang, P.; Sheng, Y.; Zhang, L.; Han, H. Fully Printable Mesoscopic Perovskite Solar Cells with Organic Silane Self-Assembled Monolayer. J. Am. Chem. Soc. 2015, 137, 1790-1793. (40) Ganesan, P.; Fu, K.; Gao, P.; Raabe, I.; Schenk, K.; Scopelliti, R.; Luo, J.; Wong, L. H.; Gratzel, M.; Nazeeruddin, M. K. A Simple Spiro-Type Hole Transporting Material for Efficient Perovskite Solar Cells. Energy Environ. Sci. 2015, 8, 1986-1991. (41) Kim, G.-W.; Kang, G.; Kim, J.; Lee, G.-Y.; Kim, H. I.; Pyeon, L.; Lee, J.; Park, T. Dopant-Free Polymeric Hole Transport Materials for Highly Efficient and Stable Perovskite Solar Cells. Energy Environ. Sci. 2016, 9, 2326-2333. (42) Liu, Y.; Hong, Z.; Chen, Q.; Chen, H.; Chang, W.-H.; Yang, Y.; Song, T.-B.; Yang, Y. Perovskite Solar Cells Employing Dopant-Free Organic Hole Transport Materials with Tunable Energy Levels. Adv. Mater. 2016, 28, 440-446. (43) Roldán-Carmona, C.; Gratia, P.; Zimmermann, I.; Grancini, G.; Gao, P.; Graetzel, M.; Nazeeruddin, M. K. High Efficiency Methylammonium Lead Triiodide Perovskite Solar Cells: The Relevance of Non-Stoichiometric Precursors. Energy Environ. Sci. 2015, 8, 3550-3556. (44) Jacobsson, T. J.; Correabaena, J. P.; Halvani, A. E.; Philippe, B.; Stranks, S. D.; 24


Page 25 of 27 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


Bouduban, M. E.; Tress, W.; Schenk, K.; Teuscher, J.; Moser, J. E. Unreacted Pbi2 as a Double-Edged Sword for Enhancing the Performance of Perovskite Solar Cells. J. Am. Chem. Soc. 2016, 138, 10331-10343. (45) Jiang, Q.; Chu, Z.; Wang, P.; Yang, X.; Liu, H.; Wang, Y.; Yin, Z.; Wu, J.; Zhang, X.; You, J. Planar-Structure Perovskite Solar Cells with Efficiency Beyond 21%. Adv. Mater. 2017, 29, 1703852. (46) Zhang, W.; Pathak, S.; Sakai, N.; Stergiopoulos, T.; Nayak, P. K.; Noel, N. K.; Haghighirad, A. A.; Burlakov, V. M.; deQuilettes, D. W.; Sadhanala, A.; Li, W.; Wang, L.; Ginger, D. S.; Friend, R. H.; Snaith, H. J. Enhanced Optoelectronic Quality of Perovskite Thin Films with Hypophosphorous Acid for Planar Heterojunction Solar Cells. Nat. Commun. 2015, 6, 10030. (47) Li, M.; Yan, X.; Kang, Z.; Liao, X.; Li, Y.; Zheng, X.; Lin, P.; Meng, J.; Zhang, Y. Enhanced Efficiency and Stability of Perovskite Solar Cells Via Anti-Solvent Treatment in Two-Step Deposition Method. ACS Appl. Mater. Interfaces 2017, 9, 7224-7231. (48) Liu, J.; Gao, C.; He, X.; Ye, Q.; Ouyang, L.; Zhuang, D.; Liao, C.; Mei, J.; Lau, W. Improved Crystallization of Perovskite Films by Optimized Solvent Annealing for High Efficiency Solar Cell. ACS Appl. Mater. Interfaces 2015, 7, 24008-24015. (49) Liu, Y.; Bag, M.; Renna, L. A.; Page, Z. A.; Kim, P.; Emrick, T.; Venkataraman, D.; Russell, T. P. Understanding Interface Engineering for High-Performance Fullerene/Perovskite Planar Heterojunction Solar Cells. Adv. Energy Mater. 2016, 6, 1501606. (50) Kim, H.-S.; Jang, I.-H.; Ahn, N.; Choi, M.; Guerrero, A.; Bisquert, J.; Park, N.-G. Control of I–V Hysteresis in Ch3nh3pbi3 Perovskite Solar Cell. J. Phys. Chem. Lett. 2015, 6, 4633-4639. (51) Li, L.; Wang, F.; Wu, X.; Yu, H.; Zhou, S.; Zhao, N. Carrier-Activated Polarization in Organometal Halide Perovskites. J. Phys. Chem. C 2016, 120, 2536-2541. (52) Li, W.; Zhang, W.; Reenen, S. V.; 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 Environ. Sci. 2016, 9, 490-498. (53) Lee, J. W.; Kim, D. H.; Kim, H. S.; Seo, S. W.; Cho, S. M.; Park, N. G. Formamidinium and Cesium Hybridization for Photo ‐

and Moisture ‐ Stable

Perovskite Solar Cell. Adv. Energy Mater. 2015, 5, 1501310. (54) Park, I. J.; Seo, S.; Park, M. A.; Lee, S.; Kim, D. H.; Zhu, K.; Shin, H.; Kim, J. Y. Effect of Rubidium Incorporation on the Structural, Electrical, and Photovoltaic Properties of Methylammonium Lead Iodide-Based Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 41898-41905. (55) Dong, H.; Wu, Z.; Xi, J.; Xu, X.; Zuo, L.; Lei, T.; Zhao, X.; Zhang, L.; Hou, X.; Jen, A. K. Y. Pseudohalide-Induced Recrystallization Engineering for Ch3nh3pbi3 Film and Its Application in Highly Efficient Inverted Planar Heterojunction Perovskite Solar Cells. Adv. Funct. Mater. 2017, 1704836. 25



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(56) Shao, Y.; Xiao, Z.; Cheng, B.; Yuan, Y.; Huang, J. Origin and Elimination of Photocurrent Hysteresis by Fullerene Passivation in Ch3nh3pbi3 Planar Heterojunction Solar Cells. Nat. Commun. 2014, 5, 5784. (57) Lin, Y.; Liang, S.; Dai, J.; Deng, Y.; Yang, W.; Yang, B.; Zheng, X.; Wang, J.; Fang, Y.; Wei, H. Π‐Conjugated Lewis Base: Efficient Trap‐Passivation and Charge‐ Extraction for Hybrid Perovskite Solar Cells. Adv. Mater. 2017, 29, 1604545. (58) Li, M.; Huan, Y.; Yan, X.; Kang, Z.; Guo, Y.; Li, Y.; Liao, X.; Zhang, R.; Zhang, Y. Efficient Yttrium(Iii) Chloride-Treated Tio2 Electron Transfer Layers for Performance-Improved and Hysteresis-Less Perovskite Solar Cells. ChemSusChem 2017, 11, 171-177.

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ToC

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Hydrophobic Polystyrene Passivation Layer for Simultaneously

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