Materials processing routes to trap-free halide perovskites

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

581 Scopus citations

Abstract

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 - Nov 12 2014

Keywords

  • defect
  • diffusion length
  • electronic traps
  • growth
  • Perovskite
  • precursor

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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