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

Accepted version
Peer-reviewed

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Article

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Abstract

Efforts to stabilize photoactive formamidinium (FA)–based halide perovskites for perovskite photovoltaics have focused on the growth of cubic formamidinium lead iodide (α-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 α-FAPbI3 thin films without any cation alloying. The templated photoactive FAPbI3 film was extremely stable against thermal, environmental, and light stressors.

Description

Keywords

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry

Journal Title

Science

Conference Name

Journal ISSN

0036-8075
1095-9203

Volume Title

374

Publisher

American Association for the Advancement of Science (AAAS)
Sponsorship
Royal Society (UF150033)
European Research Council (756962)
Engineering and Physical Sciences Research Council (EP/R023980/1)
Royal Society (NIF\R1\181365)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (841136)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (841386)
Engineering and Physical Sciences Research Council (EP/R008779/1)
European Commission Horizon 2020 (H2020) Research Infrastructures (RI) (823717)
European Commission Horizon 2020 (H2020) ERC (835073)
EPSRC (2127077)
EPSRC (EP/V012932/1)
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