Lead-free tin halide perovskite solar cells beyond 10 % efficiency
Muhammad Akmal Kamarudin a, Daisuke Hirotani b, Zhen Wang b, Kengo Hamada b, Kohei Nishimura a, Qing Shen c, Satoshi Iikubo b, Takashi Minemoto d, Kenji Yoshino e, Shuzi Hayase a
a i-Powered Energy System Reserach Center, The University of Electro-Communications
b Kyushu Institute of Technology, Japan, 204 Hibikino Wakamatsu-ku, Kitakyushu - Fukuoka, 808, Japan
c Graduate School of Informatics and Engineering, University of Electro-Communication, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan.
d Department of Electrical and Electronic Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
e Faculty of Engineering, University of Miyazaki, Gakuen-kibanadai-nishi-1-1, Miyazaki, 889-2192, Japan.
Oral, Muhammad Akmal Kamarudin, presentation 028
DOI: https://doi.org/10.29363/nanoge.iperop.2020.028
Publication date: 14th October 2019

Lead-free tin perovskite solar cells (PSCs) show the most promise to replace the more toxic lead-based perovskite solar cells. However, the efficiency is significantly less than that of lead-based PSCs as a result of low open-circuit voltage (VOC). This is due to the tendency of Sn2+ to oxidize into Sn4+ in the presence of air together with the formation of defects and traps caused by the fast crystallization of tin perovskite materials. Here, post-treatment of the tin perovskite layer with edamine Lewis base to suppress the recombination reaction in tin halide PSCs results in efficiencies higher than 10%, which is the highest reported efficiency to date for pure tin halide PSCs. Larger crystal sizes is obtained with EDA post-treatment and the VOC improved by as much as 0.1 V at an optimum EDA concentration. The X-ray photoelectron spectroscopy data suggest that the recombination reaction mainly originates from the nonstoichiometric Sn:I ratio in addition to the large Sn4+:Sn2+ ratio. The amine group in edamine bonded the undercoordinated tin, passivating the dangling bonds and defects, resulting in suppressed charge carrier recombination. This work provides an evident that the surface recombination also needs to be addressed especially in the case of tin perovskite solar cells in order to achieve better device performance.

The authors acknowledge the support from JST Mirai (JPMJMI17EA)

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