Cation and anion immobilization through chemical bonding enhancement with fluorides for stable halide perovskite solar cells

Nengxu Li, Shuxia Tao, Yihua Chen, Xiuxiu Niu, Chidozie K. Onwudinanti, Chen Hu, Zhiwen Qiu, Ziqi Xu, Guanhaojie Zheng, Ligang Wang, Yu Zhang, Liang Li, Huifen Liu, Yingzhuo Lun, Jiawang Hong, Xueyun Wang, Yuquan Liu, Haipeng Xie, Yongli Gao, Yang BaiShihe Yang, Geert Brocks, Qi Chen, Huanping Zhou*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

159 Citations (Scopus)

Abstract

Defects play an important role in the degradation processes of hybrid halide perovskite absorbers, impeding their application for solar cells. Among all defects, halide anion and organic cation vacancies are ubiquitous, promoting ion diffusion and leading to thin-film decomposition at surfaces and grain boundaries. Here, we employ fluoride to simultaneously passivate both anion and cation vacancies, by taking advantage of the extremely high electronegativity of fluoride. We obtain a power conversion efficiency of 21.46% (and a certified 21.3%-efficient cell) in a device based on the caesium, methylammonium (MA) and formamidinium (FA) triple-cation perovskite (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 ) 3 treated with sodium fluoride. The device retains 90% of its original power conversion efficiency after 1,000 h of operation at the maximum power point. With the help of first-principles density functional theory calculations, we argue that the fluoride ions suppress the formation of halide anion and organic cation vacancies, through a unique strengthening of the chemical bonds with the surrounding lead and organic cations.

Original languageEnglish
Pages (from-to)408-415
Number of pages8
JournalNature energy
Volume4
Issue number5
DOIs
Publication statusPublished - 1 May 2019

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