Alkali-Cation-Enhanced Benzylammonium Passivation for Efficient and Stable Perovskite Solar Cells Fabricated Through Sequential Deposition

Jie Cao, Junke Jiang, Nan Li, Yifan Dong, Yongheng Jia, Shuxia Tao (Corresponding author), Ni Zhao (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)

Abstract

Two-step sequential deposition has been shown as an effective method to improve the quality of perovskite films and performance of perovskite solar cells (PSCs). In this work, we have developed a two-step sequential deposition method, incorporating an alkali cation (e.g., Cs+) and a benzylammonium (BA+) cation in formamidinium (FA+)-based perovskite thin films for highly efficient and stable PSCs. By combining experimental characterizations and theoretical calculations, we demonstrate that not only the co-incorporation of alkali cations and BA+ significantly improves crystallinity and orientational growth of perovskite films, but also Cs+ enhances passivation effect of BA+ ions on perovskite surface via enhanced NH…I hydrogen bonding. In particular, inclusion of Cs+ in BA+-passivated perovskites promotes the preferred orientation of defect-free (1 0 0) facets. As a result, we observed remarkable improvements in both open-circuit voltage and fill factor of formamidinium-benzylammonium-cesium (FABACs)-based PSCs, achieving a champion efficiency of 22.5%. More importantly, the FABACs perovskite films demonstrated superior resistance to humidity and photo-thermal stress, and the perovskite-based devices (without encapsulation) retained over 95% of the initial efficiency after exposure to air for 2 months. Manipulating perovskite composition by combining small alkali and large organic cations in two-step sequential deposition provides a new path to highly efficient and stable perovskite devices.
Original languageEnglish
Pages (from-to)19357-19366
Number of pages10
JournalJournal of Materials Chemistry A
Volume8
Issue number37
DOIs
Publication statusPublished - 7 Oct 2020

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