Tuning the A-Site Cation Composition of Lead-Free Perovskite for Efficient Mesoporous Perovskite Solar Cells.
Nguyen Bich Phuong a, Jung Hye Ri a, Nguyen Thi Thu Trang a, Yoon Seokhyun a, William Jo a
a Department of Physics, Ewha Womans University, 52, Ewhayeodaegil, Seodaemungu, , Seoul, 3760, Korea, Republic of
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Poster, Nguyen Bich Phuong, 153
Publication date: 23rd October 2018

Methylammonium tin iodide MASnI3 (MA = CH3NH3) has a similar absorption coefficient, optical conductivity, and elastic constant compared to Pb-based analogs. Based on the excellent optical and electrical properties, solar cells based on MASnI3 should have a potentially high PCE and be comparable with MAPbI3 solar cells. Most recent high-performance Sn-based perovskite solar cells are mainly based on formamidinium tin iodide FASnI3 (FA = HC(NH2)2) materials because of their better air stability than that of MASnI3. By replacing MA with FA, the extent of Sn oxidation can reduce, leading to reduce leakage current, increase recombination lifetime, and enhanced the device performance. In this study, we reveal the role of mixing the organic cation FA and MA in the crystallization of the FA1-xMAxSnI3 perovskite in the mesoporous devices. The local quality of morphology and local electrical properties were investigated by using scanning probe microscopy. The band bending at the grain boundaries is the most probable reason for the change in the electrical properties at the local surface of the FA1-xMAxSnI3 thin films. These insights and the associated engineering efforts led to a significantly improved power conversion efficiency of the FA0.75MA0.25SnI3 of 5.2%, which has been excellent efficiency for the Sn-based perovskite solar cells with regular mesoporous structure until now. 


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