Stabilized tilted-octahedra halide perovskites inhibit local formation of performance-limiting phases

Tiarnan A.S. Doherty, Satyawan Nagane, Dominik J. Kubicki, Young Kwang Jung, Duncan N. Johnstone, Affan N. Iqbal, Dengyang Guo, Kyle Frohna, Mohsen Danaie, Elizabeth M. Tennyson, Stuart Macpherson, Anna Abfalterer, Miguel Anaya, Yu Hsien Chiang, Phillip Crout, Francesco Simone Ruggeri, Sean M. Collins, Clare P. Grey, Aron Walsh, Paul A. MidgleySamuel D. Stranks

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Efforts to stabilize photoactive formamidinium (FA)–based halide perovskites for perovskite photovoltaics have focused on the growth of cubic formamidinium lead iodide (a-FAPbI3) phases by empirically alloying with cesium, methylammonium (MA) cations, or both. We show that such stabilized FA-rich perovskites are noncubic and exhibit ~2° octahedral tilting at room temperature. This tilting, resolvable only with the use of local nanostructure characterization techniques, imparts phase stability by frustrating transitions from photoactive to hexagonal phases. Although the bulk phase appears stable when examined macroscopically, heterogeneous cation distributions allow microscopically unstable regions to form; we found that these transitioned to hexagonal polytypes, leading to local trap-assisted performance losses and photoinstabilities. Using surface-bound ethylenediaminetetraacetic acid, we engineered an octahedral tilt into pure a-FAPbI3 thin films without any cation alloying. The templated photoactive FAPbI3 film was extremely stable against thermal, environmental, and light stressors.

Original languageEnglish
Pages (from-to)1598-1605
Number of pages8
JournalScience
Volume374
Issue number6575
DOIs
StatePublished - 24 Dec 2021

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