First-principles calculations of defect structures in Sn perovskite solar cell materials
Mai Otake a, Suzune Omori a, Masanori Kaneko b, Giacomo Giorgi c, Koichi Yamashita b, Azusa Muraoka a
a Japan Women's University, 2-8-1,Mejirodai,Bunkyo-ku, Tokyo, Japan
b Yokohama City University
c The University of Perugia
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP24)
Tokyo, Japan, 2024 January 21st - 23rd
Organizers: Qing Shen and James Ryan
Poster, Mai Otake, 099
Publication date: 18th October 2023

Among perovskite solar cells, which are the next generation of solar cells, Sn perovskite solar cells have the advantages of being free of toxic lead and having high thermal stability, but low photoelectric conversion efficiency is an issue. One of the main reasons for this is "defects”. When defects exist in the crystal, deep levels, or defect levels, are generated in the band gap. These defect levels trap carriers and induce recombination, leading to a decrease in energy exchange efficiency.[1][2] In this study, we analyzed the defect structures of FASnI3 and FA2SnGeI6, which contain FA with high thermal stability, and MASnI3 and MA2SnGeI6, which contain MA, whose photoelectric conversion efficiency has been increasing recently, by calculating defect levels and defect formation energy by structural optimization, band structure, density of states, dielectric constant, and chemical potential using first principles calculation to find a clue for improving energy conversion efficiency.

As a result, it was found that in FASnI3 and FA2SnGeI6 containing FA molecules, the chemical potentials were set to I-poor and Sn-rich conditions to prevent the formation of defect levels, which is beneficial for the photoelectric conversion efficiency. In addition, MASnI3 is superior to structures containing FA molecules because defect levels are less likely to form and are more stable under all conditions. The results on MA2SnGeI6 will be presented in our poster.

We acknowledge financial support from NEDO project (“Development of materials for Pb free perovskite tandem solar cells”) on international joint study. We would like to thank to Prof. Hayase of The University of Electro-Communications for fruitful discussions based on experiments of perovskite solar cell devices. This work used the supercomputer MASAMUNE-IMR at the Institute for Materials Research.

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