Accelerated Lifetime Testing of Organic–Inorganic Perovskite Solar

Letter www.acsami.org

Accelerated Lifetime Testing of Organic−Inorganic Perovskite Solar Cells Encapsulated by Polyisobutylene Lei Shi,† Trevor L. Young,† Jincheol Kim,† Yun Sheng,‡ Lei Wang,‡ Yifeng Chen,‡ Zhiqiang Feng,‡ Mark J. Keevers,† Xiaojing Hao,† Pierre J. Verlinden,‡ Martin A. Green,† and Anita W. Y. Ho-Baillie*,† †

The Australian Centre for Advanced Photovoltaics (ACAP), School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052, Australia ‡ Trina Solar, No.2 Trina Road, Trina PV Industrial Park, Xinbei District, Changzhou, Jiangsu 213031, China S Supporting Information *

ABSTRACT: Metal halide perovskite solar cells (PSCs) have undergone rapid progress. However, unstable performance caused by sensitivity to environmental moisture and high temperature is a major impediment to commercialization of PSCs. In the present work, a lowtemperature, glass−glass encapsulation technique using high performance polyisobutylene (PIB) as the moisture barrier is investigated on planar glass/FTO/TiO2/FAPbI3/PTAA/gold perovskite solar cells. PIB was applied as either an edge seal or blanket layer. Electrical connections to the encapsulated PSCs were provided by either the FTO or Au layers. Results of a “calcium test” demonstrated that a PIB edge-seal effectively prevents moisture ingress. A shelf life test was performed and the PIBsealed PSC was stable for at least 200 days. Damp heat and thermal cycling tests, in compliance with IEC61215:2016, were used to evaluate different encapsulation methods. Current−voltage measurements were performed regularly under simulated AM1.5G sunlight to monitor changes in PCE. The best results we have achieved to date maintained the initial efficiency after 540 h of damp heat testing and 200 thermal cycles. To the best of the authors’ knowledge, these are among the best damp heat and thermal cycle test results for perovskite solar cells published to date. Given the modest performance of the cells (8% averaged from forward and reverse scans) especially with the more challenging FAPbI3 perovskite material tested in this work, it is envisaged that better stability results can be further achieved when higher performance perovskite solar cells are encapsulated using the PIB packaging techniques developed in this work. We propose that heat rather than moisture was the main cause of our PSC degradation. Furthermore, we propose that preventing the escape of volatile decomposition products from the perovskite solar cell materials is the key for stability. PIB encapsulation is a very promising packaging solution for perovskite solar cells, given its demonstrated effectiveness, ease of application, low application temperature, and low cost. KEYWORDS: perovskite solar cell, low cost encapsulation, stability, IEC environmental test, accelerated test

■

INTRODUCTION Although the past few years have seen the emergence1 and rapid development2 of PSCs with phenomenal growth in power conversion efficiency (PCE) to the recently independently certified record of 22.1%,3 cell instability remains a major barrier to commercialization. Poor thermal stability limits the maximum fabrication, encapsulation, and operational temperatures of a solar cell. Both the perovskite absorber and the hole transport layer (HTL) have been found to degrade at elevated temperature.4 Cesium (Cs) and formamidinium (FA = HC(NH2)2+)-based cells have been shown to have higher thermal stability than methylammonium (MA = CH3NH3+) based cells.4−7 Another major instability factor is the decomposition of perovskite absorbers, e.g., MAPbI3 and FAPbI3, upon exposure to moisture.8−11 Addition of Rubidium © 2017 American Chemical Society

(Rb) and the use of layered perovskite can improve moisture stability.12,13 Various interface and/or protective layers has been demonstrated to reduce moisture ingress into the device such as epoxy/Ag paint,14 ZnO,15 carbon,16,17 Cr2O3,18 Cr,19 Al2O3,20,21 MoO3,22 and ITO.23 Bush et al. demonstrated the first stability testing that passed damp heat of IEC61215:2016 by using ITO as the capping layer and glass/EVA/butyl rubber as the packaging materials.24 The PSCs involved had steady efficiencies at about 10%. However, most stability testing including those exceeding 1000 h25,26 were conducted in uncontrolled conditions or under nonstandardized testing Received: May 29, 2017 Accepted: July 12, 2017 Published: July 12, 2017 25073

DOI: 10.1021/acsami.7b07625 ACS Appl. Mater. Interfaces 2017, 9, 25073−25081

Letter

ACS Applied Materials & Interfaces

processing temperature and cost. PIB can be applied as an edge sealant at low temperatures (room temperature to 160 °C). It has been widely used as a spacer between double-glazed windowpanes. PIB has a very low water vapor transmission rate (WVTR), 1 × 10−2 to 1 × 10−3 g/(m2 day) compared to 16 g/ (m2 day) for UV-cured epoxy and 28 g/(m2 day) for EVA (see Table 1). In the photovoltaics industry, PIB is used to edge-seal CIGS thin-film glass/glass modules.28 It has been reported that a 10 mm wide PIB edge seal can stop moisture ingress under damp heat testing (85 °C, 85% RH) for more than 1000 h.32 The low water vapor transmission rate, low application temperature, and low cost of PIB could make it an ideal encapsulant or edge sealant for PSCs. In this work, glass/PIB/glass encapsulation methods were investigated to evaluate their effectiveness in improving the stability of PSCs for the first time. The perovskite solar cells used in this work have a structure of glass/FTO/c-TiO2/ FAPbI3/PTAA/gold as a continuation of previous work which takes advantage of the simplicity of the cell structure and the better thermal stability than conventional MAPbI3/spiroOMeTAD based PSC.4 The PCE (average of Jsc → Voc and Voc → Jsc scans) is typically in the range of 8−9% with observable hysteresis (Table S1). Two accelerated lifetime tests, damp heat (DH) and thermal cycling (TC), were performed according to IEC61215:2016, which is the widely accepted standard for commercial PV modules. Exposure of the encapsulated devices to ambient temperature and humidity was also studied. Glass/EVA/glass and glass/UV-cured epoxy/ glass encapsulation schemes were also investigated, for comparison.

regimes. This makes it difficult for the various device stabilization strategies to be compared in a meaningful way. Thin-film devices such as copper−indium−gallium−selenide (CIGS) solar cells and organic light emitting diodes (OLED) degrade upon exposure to environmental air and water.27−29 The fact that commercial solutions existing for encapsulating and stabilizing these thin-film devices implies that similar commercially viable solutions might be developed for perovskite solar cells as well. UV-cured epoxy, which is widely used in commercial OLED products, has been used to encapsulate research type PSCs.30,31 It is, however, much more expensive than the common encapsulant (ethylene-vinyl acetate (EVA) plus butyle edge sealant) used in commercial thin film (e.g., CIGS) photovoltaic modules (see Table 1). In addition to a Table 1. Properties and Prices of PIB, EVA, and UV-Curable Epoxy for a Typical Glass−glass Encapsulated Thin-Film Solar Modulea PIB WVTR (g/(m2 day)) application temperature (°C) material cost when used as an edge sealant (US$) material cost when used as an encapsulant (US$)

EVA

UV-cured epoxy

1 × 10−2 to 1 × 10−3 RT to 160 0.22

28

16

140−150 NA

RT 145

6.8

3.3

N/A

a

See the Supporting Information for a detailed description. Modules area = 0.94 m2; RT = room temperature.

■

low-cost encapsulant, PSCs also require a low-temperature encapsulation process because of their low thermal tolerance, which is below 200 °C for all PSCs that use organic cation (e.g., MA and/or FA) as well as organic HTL (e.g., spiro-OMeTAD (2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobi fl u o r e n e ) o r PT A A ( p o ly [ b i s ( 4 - p h e n y l ) ( 2 , 4 , 6 trimethylphenyl)amine])). High performance PIB based moisture barrier meets both above requirements in terms of

EXPERIMENTAL SECTION

The perovskite solar cells were fabricated according to the procedures outlined below and detailed in the Supporting Information. PIB, which is supplied as a tape, was first cut into the desired width and applied to the 1 mm thick cover glass. The cover glass with PIB was then applied over the perovskite solar cell. The whole structure was finally hotpressed in a solar module laminator with a background pressure of

Figure 1. Cross-sectional schematics and plan-view photographs from the FTO glass side of PSCs encapsulated by three methods (not to scale). In method 1, PIB is applied over a thin gold film, which is the positive electrical feedthrough for the cell. In methods 2 and 3, both electrical feedthroughs are provided by the FTO layer. Methods 1 and 2 use PIB as an edge seal, whereas in method 3, PIB blankets the entire area under the cover glass. 25074

DOI: 10.1021/acsami.7b07625 ACS Appl. Mater. Interfaces 2017, 9, 25073−25081

Letter

ACS Applied Materials & Interfaces Table 2. Specification of the Two IEC61215:2016 Tests Carried out in This Work

a

tests

conditions

duration

settlement time (h)a

damp heat (DH) thermal cycling (TC)

85 °C, 85% RH −40 to 85 °C dwell 15 min @ −40 and 85 °C

up to 1000 h up to 200 cycles

2−4 >1

The settlement time is a relaxation period following exposure to the test conditions, before the solar cells are remeasured.

300−400 mTorr for 10 min at 90 °C which is sufficiently high to facilitate the encapsulation process including bonding and the removal of air bubbles with minimum thermal stress on the cells during the encapsulation process before the IEC tests (with maximum temperature at 85 °C). The encapsulated devices were then stored in dry air (540 h 35 cycles 75 cycles >200 cycles

200 h 300 h N/A 54 cycles >200 cycles N/A

Jsc (58%) and FF (42%) FF (82%) N/A Jsc (45%) and FF (45%) FF (100%) N/A

no. of samples a

2 3 3 2 4 4

One of these two samples degraded severely in the first couple hours of the test and hence its result is not included in Figure 2. bRelative contribution at T50. a

25079

DOI: 10.1021/acsami.7b07625 ACS Appl. Mater. Interfaces 2017, 9, 25073−25081

Letter

ACS Applied Materials & Interfaces

(18) Kaltenbrunner, M.; Adam, G.; Głowacki, E. D.; Drack, M.; Schwödiauer, R.; Leonat, L.; Apaydin, D. H.; Groiss, H.; Scharber, M. C.; White, M. S.; Sariciftci, N. S.; Bauer, S. Flexible High Power-PerWeight Perovskite Solar Cells with Chromium Oxide−Metal Contacts for Improved Stability in Air. Nat. Mater. 2015, 14, 1032−1039. (19) Guerrero, A.; You, J.; Aranda, C.; Kang, Y. S.; Garcia-Belmonte, G.; Zhou, H.; Bisquert, J.; Yang, Y. Interfacial Degradation of Planar Lead Halide Perovskite Solar Cells. ACS Nano 2016, 10, 218−224. (20) Dong, X.; Fang, X.; Lv, M.; Lin, B.; Zhang, S.; Ding, J.; Yuan, N. Improvement of the Humidity Stability of Organic−Inorganic Perovskite Solar Cells using Ultrathin Al2O3 Layers Prepared by Atomic Layer Deposition. J. Mater. Chem. A 2015, 3, 5360−5367. (21) Guarnera, S.; Abate, A.; Zhang, W.; Foster, J. M.; Richardson, G.; Petrozza, A.; Snaith, H. J. Improving the Long-Term Stability of Perovskite Solar Cells with a Porous Al2O3 Buffer Layer. J. Phys. Chem. Lett. 2015, 6, 432−437. (22) Hou, F.; Su, Z.; Jin, F.; Yan, X.; Wang, L.; Zhao, H.; Zhu, J.; Chu, B.; Li, W. Efficient and Stable Planar Heterojunction Perovskite Solar Cells with a MoO3/PEDOT:PSS Hole Transporting Layer. Nanoscale 2015, 7, 9427−9432. (23) Bush, K. A.; Bailie, C. D.; Chen, Y.; Bowring, A. R.; Wang, W.; Ma, W.; Leijtens, T.; Moghadam, F.; McGehee, M. D. Thermal and Environmental Stability of Semi-transparent Perovskite Solar Cells for Tandems Enabled by a Solution-processed Nanoparticle Buffer Layer and Sputtered ITO Electrode. Adv. Mater. 2016, 28, 3937−3943. (24) Bush, K. A.; Palmstrom, A. F.; Yu, Z. J.; Boccard, M.; Cheacharoen, R.; Mailoa, J. P.; Mcmeekin, D. P.; Hoye, R. L. Z.; Bailie, C. D.; Leijtens, T.; Peters, I. M.; Minichetti, M. C.; Rolston, N.; Prasanna, R.; Sofia, S.; Harwood, D.; Ma, W.; Moghadam, F.; Snaith, H. J.; Buonassisi, T.; Holman, Z. C.; Bent, S. F.; Mcgehee, M. D. 23.6%-efficient Monolithic Perovskite-Silicon Tandem Solar Cells with Improved Stability. Nat. Energy 2017, 2, 17009. (25) Yang, D.; Yang, Z.; Qin, W.; Zhang, Y.; Liu, S. F.; Li, C. Alternating Precursor Layer Deposition for Highly Stable Perovskite Films Towards Efficient Solar Cells using Vacuum Deposition. J. Mater. Chem. A 2015, 3, 9401−9405. (26) Tripathi, N.; Yanagida, M.; Shirai, Y.; Masuda, T.; Han, L.; Miyano, K. Hysteresis-free and Highly Stable Perovskite Solar Cells Produced via a Chlorine-mediated Interdiffusion Method. J. Mater. Chem. A 2015, 3, 12081−12088. (27) Olsen, L.; Kundu, S.; Gross, M.; Joly, A.Damp Heat Effects on CIGSSe and CdTe Cells Proceedings of the Department of Energy SETP Review Meeting; Denver, CO, April 17−19, 2007 ; Department of Energy: Washington, D.C., 2007. (28) Sundaramoorthy, R.; Pern, F. J.; Gessert, T. Preliminary DampHeat Stability Studies of Encapsulated CIGS Solar Cells. Proc. SPIE 7773, Reliab. Photovolt. Cells, Modul. Components, Syst. III 2010, 77730Q. (29) Jorgensen, M.; Norrman, K.; Krebs, F. C. Stability/Degradation of Polymer Solar Cells. Sol. Energy Mater. Sol. Cells 2008, 92, 686−714. (30) Han, Y.; Meyer, S.; Dkhissi, Y.; Weber, K.; Pringle, J.; Bach, U.; Spiccia, L.; Cheng, Y.-B. Degradation Observations of Encapsulated Planar CH3NH3PbI3 Perovskite Solar Cells at High Temperatures and Humidity. J. Mater. Chem. A 2015, 3, 8139−8147. (31) Matteocci, F.; Cina, L.; Lamanna, E.; Cacovich, S.; Divitini, G.; Midgley, P. A.; Ducati, C.; Di Carlo, A. Encapsulation for Long-Term Stability Enhancement of Perovskite Solar Cells. Nano Energy 2016, 30, 162−172. (32) Kempe, M. D.; Panchagade, D.; Reese, M. O.; Dameron, A. A. Modeling Moisture Ingress Through Polyisobutylene based Edgeseals. Prog. Photovoltaics 2015, 23, 570−581. (33) Adams, J.; Salvador, M.; Lucera, L.; Langner, S.; Spyropoulos, G. D.; Fecher, F. W.; Voigt, M. M.; Dowland, S. A.; Osvet, A.; Egelhaaf, H. J.; Brabec, C. J. Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance. Adv. Energy Mater. 2015, 5, 1501065. (34) Shao, Y.; Xiao, Z.; Bi, C.; Yuan, Y.; Huang, J. Origin and Elimination of Photocurrent Hysteresis by Fullerene Passivation in

Facility (AMMRF) and Cho Fai Jonathan Lau for SEM imaging.

■

REFERENCES

(1) Green, M. A.; Ho-Baillie, A.; Snaith, H. J. The Emergence of Perovskite Solar Cells. Nat. Photonics 2014, 8, 506−514. (2) Green, M. A.; Ho-Baillie, A. W.-Y. Perovskite Solar Cells: The Birth of a New Era in Photovoltaics. ACS Energy Lett. 2017, 2, 822− 830. (3) Green, M. A.; Emery, K.; Hishikawa, Y.; Warta, W.; Dunlop, E. D.; Levi, D. H.; Ho-Baillie, A. W. Y. Solar Cell Efficiency Tables (version 49). Prog. Photovoltaics 2017, 25, 3−13. (4) Kim, J.; Park, N.; Yun, J. S.; Huang, S.; Green, M. A.; Ho-Baillie, A. W. Y. An Effective Method of Predicting Perovskite Solar Cell Lifetime−Case Study on Planar CH3NH3PbI3 and HC(NH2)2PbI3 Perovskite Solar Cells and Hole Transfer Materials of Spiro-OMeTAD and PTAA. Sol. Sol. Energy Mater. Sol. Cells 2017, 162, 41−46. (5) Kim, J.; Yun, J. S.; Wen, X.; Soufiani, A. M.; Lau, C.-F. J.; Wilkinson, B.; Seidel, J.; Green, M. A.; Huang, S.; Ho-Baillie, A. W.-Y. Nucleation and Growth Control of HC(NH2)2PbI3 for Planar Perovskite Solar Cell. J. Phys. Chem. C 2016, 120, 11262−11267. (6) Lau, C. F. J.; Deng, X.; Ma, Q.; Zheng, J.; Yun, J. S.; Green, M. A.; Huang, S.; Ho-Baillie, A. W. Y. CsPbIBr2 Perovskite Solar Cell by Spray-Assisted Deposition. ACS Energy Lett. 2016, 1, 573−577. (7) Ma, Q.; Huang, S.; Wen, X.; Green, M. A.; Ho-Baillie, A. W. Y. Hole Transport Layer Free Inorganic CsPbIBr2 Perovskite Solar Cell by Dual Source Thermal Evaporation. Adv. Energy Mater. 2016, 6, 1502202. (8) Christians, J. A.; Miranda Herrera, P. A.; 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. (9) 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. (10) Noh, J. H.; Im, S. H.; Heo, J. H.; Mandal, T. N.; Seok, S. Il. Chemical Management for Colorful, Efficient, and Stable Inorganic − Organic Hybrid Nanostructured Solar Cells. Nano Lett. 2013, 13, 1764−1769. (11) Ito, S. Research Update: Overview of Progress About Efficiency and Stability on Perovskite Solar Cells. APL Mater. 2016, 4, 091504. (12) Tsai, H.; Nie, W.; Blancon, J.-C.; Stoumpos, C. C.; Asadpour, R.; Harutyunyan, B.; Neukirch, A. J.; Verduzco, R.; Crochet, J. J.; Tretiak, S.; Pedesseau, L.; Even, J.; Alam, M. A.; Gupta, G.; Lou, J.; Ajayan, P. M.; Bedzyk, M. J.; Kanatzidis, M. G.; Mohite, A. D. Highefficiency Two-dimensional Ruddlesden−Popper perovskite Solar Cells. Nature 2016, 536, 312−316. (13) Zhang, M.; Yun, J. S.; Ma, Q.; Zheng, J.; Lau, C.-F. J.; Deng, X.; Kim, J.; Kim, D.; Seidel, J.; Green, M. A.; Huang, S.; Ho-Baillie, A. W.Y. High Efficiency Rubidium Incorporated Perovskite Solar Cells by Gas Quenching. ACS Energy Lett. 2017, 2, 438−444. (14) Wei, Z.; Zheng, X.; Chen, H.; Long, X.; Wang, Z.; Yang, S. A Multifunctional C + Epoxy/Ag-paint Cathode Enables Efficient and Stable Operation of Perovskite Solar Cells in Watery Environments. J. Mater. Chem. A 2015, 3, 16430−16434. (15) You, J.; Meng, L.; Song, T.-B.; Guo, T.-F.; Yang, Y.; Chang, W.H.; Hong, Z.; Chen, H.; Zhou, H.; Chen, Q.; Liu, Y.; De Marco, N.; Yang, Y. Improved Air Stability of Perovskite Solar Cells via SolutionProcessed Metal Oxide Transport Layers. Nat. Nanotechnol. 2015, 11, 75−81. (16) Habisreutinger, S. N.; Leijtens, T.; Eperon, G. E.; Stranks, S. D.; Nicholas, R. J.; Snaith, H. J. Carbon Nanotube/Polymer Composites as a Highly Stable Hole Collection Layer in Perovskite Solar Cells. Nano Lett. 2014, 14, 5561−5568. (17) 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. 25080

DOI: 10.1021/acsami.7b07625 ACS Appl. Mater. Interfaces 2017, 9, 25073−25081

Letter

ACS Applied Materials & Interfaces CH3NH3PbI3 Planar Heterojunction Solar Cells. Nat. Commun. 2014, 5, 5784. (35) Li, X.; Tschumi, M.; Han, H.; Babkair, S. S.; Alzubaydi, R. A.; Ansari, A. A.; Habib, S. S.; Nazeeruddin, M. K.; Zakeeruddin, S. M.; Grätzel, M. Outdoor Performance and Stability under Elevated Temperatures and Long-Term Light Soaking of Triple-Layer Mesoporous Perovskite Photovoltaics. Energy Technol. 2015, 3, 551. (36) 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. (37) Deng, X.; Wen, X.; Lau, J.; Young, T.; Yun, J.; Green, M.; Huang, S.; Ho-Baillie, A. W. Y. Electric Field Induced Reversible and Irreversible Photoluminescence Responses in Methylammonium Lead Iodide Perovskite. J. Mater. Chem. C 2016, 4, 9060−9068. (38) Soufiani, A. M.; Hameiri, Z.; Meyer, S.; Lim, S.; Tayebjee, M. J. Y.; Yun, J. S.; Ho-Baillie, A.; Conibeer, G. J.; Spiccia, L.; Green, M. A. Lessons Learnt from Spatially Resolved Electro- and Photoluminescence Imaging: Interfacial Delamination in CH3NH3PbI3 Planar Perovskite Solar Cells upon Illumination. Adv. Energy Mater. 2017, 7, 1602111. (39) Bailie, C. D.; Unger, E. L.; Zakeeruddin, S. M.; Grätzel, M.; McGehee, M. D. Melt-infiltration of Spiro-OMeTAD and Thermal Instability of Solid-State Dye-Sensitized Solar Cells. Phys. Chem. Chem. Phys. 2014, 16, 4864. (40) Stoumpos, C. C.; Malliakas, C. D.; Kanatzidis, M. G. Organic Tin and Lead Iodide Perovskites with Organic Cations: Unique Semiconductors, with Phase Transitions and Near-Infrared Photoluminescent Properties. Inorg. Chem. 2013, 52, 9019−9038. (41) Koh, T. M.; Fu, K.; Fang, Y.; Chen, S.; Sum, T. C.; Mathews, N.; Mhaisalkar, S. G.; Boix, P. P.; Baikie, T. Formamidinium-Containing Metal-Halide: An Alternative Material for Near-IR Absorption Perovskite Solar Cells. J. Phys. Chem. C 2014, 118, 16458. (42) Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. Il. Compositional Engineering of Perovskite Materials for High-performance Solar Cells. Nature 2015, 517, 476−480. (43) Yi, C.; Luo, J.; Meloni, S.; Boziki, A.; Ashari-Astani, N.; Grätzel, C.; Zakeeruddin, S. M.; Röthlisberger, U.; Grätzel, M. Entropic Stabilization of Mixed A-Cation ABX3 Metal Halide Perovskites for High Performance Perovskite Solar Cells. Energy Environ. Sci. 2016, 9, 656−662. (44) Pool, V. L.; Dou, B.; Van Campen, D. G.; Klein, T. R.; Barnes, F. S.; Shaheen, S. E.; Ahmad, M. I.; Van Hest, M. F. A. M.; Toney, M. F. Thermal Engineering of FAPbI3 Perovskite Material via Radiative Thermal Annealing and in situ XRD. Nat. Commun. 2017, 8, 14075. (45) Smecca, E.; Numata, Y.; Deretzis, I.; Pellegrino, G.; Boninelli, S.; Miyasaka, T.; La Magna, A.; Alberti, A. Stability of Solution-processed MAPbI3 and FAPbI3 Layers. Phys. Chem. Chem. Phys. 2016, 18, 13413−13422. (46) Wang, S.; Sina, M.; Parikh, P.; Uekert, T.; Shahbazian, B.; Devaraj, A.; Meng, Y. S. Role of 4-tert-Butylpyridine as a Hole Transport Layer Morphological Controller in Perovskite Solar Cells. Nano Lett. 2016, 16, 5594−5600.

25081

DOI: 10.1021/acsami.7b07625 ACS Appl. Mater. Interfaces 2017, 9, 25073−25081