How to Make Dense and Flat Perovskite Layers for >20% Efficient Solar Cells: Oriented, Crystalline Perovskite Intermediates and Their Thermal Conversion

• Published in: Bulletin of the Chemical Society of Japan Vol. 92; no. 12; pp. 1972 - 1979
• Main Authors: Ozaki, Masashi, Nakaike, Yumi, Shimazaki, Ai, Jung, Mina, Maruyama, Naoki, Yakumaru, Shinya, Rafieh, Alwani Imanah, Ekanayake, Piyasiri, Saito, Takashi, Shimakawa, Yuichi, Sasamori, Takahiro, Murata, Yasujiro, Murdey, Richard, Wakamiya, Atsushi
• Format: Journal Article
• Language: English
• Published: Tokyo The Chemical Society of Japan 15.12.2019; Chemical Society of Japan
• Subjects: Annealing; Conversion coating; Crystallites; Dimethyl sulfoxide; Energy conversion efficiency; Grain size; Materials Innovation; Perovskites; Photovoltaic cells; Reproducibility; Solar cells; Spin coating; Thermal transformations; Thin films; Mechanism; Perovskite solar cells; Solution process
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.20190241

CH3NH3PbI3 (MAPbI3) perovskite layers can be obtained by thermal annealing thin films of the intermediate dimethyl sulfoxide (DMSO) intercalated complex, MA2Pb3I8·2DMSO. In the present work, the formation, structure, and thermal transformation of the intermediate complex in both bulk and thin film form is examined in detail. The grain size and orientation of the intermediate crystallites in the solvent-intercalated thin film material is shown to directly influence the flatness of the annealed perovskite layer. Flat-lying orientation of the small needle-like intermediate crystallites is found to yield dense and flat perovskite layers. Optimized spin coating and annealing processes are developed for the formation and thermal conversion, respectively, of the intermediate film. Based on these methods, MAPbI3 perovskite solar cells with high power conversion efficiency (maximum ∼20.3%) were obtained with high reproducibility.