Materials Processing Routes to Trap-Free Halide Perovskites

Andrei Buin, Patrick Pietsch, Jixian Xu, Oleksandr Voznyy, Alexander H. Ip, Riccardo Comin, Edward H. Sargent

Research output: Contribution to journalArticlepeer-review

458 Scopus citations

Abstract

© 2014 American Chemical Society. Photovoltaic devices based on lead iodide perovskite films have seen rapid advancements, recently achieving an impressive 17.9% certified solar power conversion efficiency. Reports have consistently emphasized that the specific choice of growth conditions and chemical precursors is central to achieving superior performance from these materials; yet the roles and mechanisms underlying the selection of materials processing route is poorly understood. Here we show that films grown under iodine-rich conditions are prone to a high density of deep electronic traps (recombination centers), while the use of a chloride precursor avoids the formation of key defects (Pb atom substituted by I) responsible for short diffusion lengths and poor photovoltaic performance. Furthermore, the lowest-energy surfaces of perovskite crystals are found to be entirely trap-free, preserving both electron and hole delocalization to a remarkable degree, helping to account for explaining the success of polycrystalline perovskite films. We construct perovskite films from I-poor conditions using a lead acetate precursor, and our measurement of a long (600 ± 40 nm) diffusion length confirms this new picture of the importance of growth conditions.
Original languageEnglish (US)
Pages (from-to)6281-6286
Number of pages6
JournalNano Letters
Volume14
Issue number11
DOIs
StatePublished - Oct 13 2014
Externally publishedYes

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