Theoretical study of the molecular passivation effect of Lewis base/acid on Sn perovskite surface defects
Makito Takagi a, Takumi Naito a, Masanori Tachikawa a, Koichi Yamashita a, Tomomi Shimazaki a
a Yokohama City University
Poster, Makito Takagi, 067
Publication date: 24th October 2023

 In recent years, extensive research has been conducted to improve the power conversion efficiency (PCE) of perovskite solar cells. However, the charge carriers are easily trapped by the defect sites located at the interface between the perovskite light-absorbing layer and the electrode, which decreases the PCE. To reduce the number of defect sites, the passivation technique is frequently employed to coat small molecules on the perovskite surface during the manufacturing process.

 In this study, to clarify the passivation mechanism from the molecular viewpoint, we performed density functional theory (DFT) calculations to target Pb-free Sn perovskites (CH3NH2SnI3). We investigated the passivation effect of Lewis base/acid molecules, such as ethylene diamine (EDA) and iodopentafluorobenzene (IPFB), and discussed the behaviors of the defect levels within the bandgap as they have strong negative impacts on the PCE. Our calculations show that the adsorption of EDA/IPFB on the Sn perovskite surface can remove the defect levels from the bandgap. Furthermore, we discuss the importance of interactions with molecular orbitals and defect level using a visualization technique based on the electron density.[1]

This work is partly supported by Grant-in-Aid for Scientific Research (KAKENHI) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Grant Numbers 21H00026 and 22K05038. We acknowledge financial support from NEDO project (“Development of materials for Pb free perovskite tandem solar cells”) on international collaboration. This work used computational resources of ITO provided by Research Institute for Information Technology, Kyushu University through the HPCI System Research Project (Project ID: hp220061). We would like to thank to Prof. Hayase of The University of Electro-Communications for fruitful discussions based on experiments of MASnI3 perovskite solar cell devices.

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