Materials Processing Routes to Trap-Free Halide Perovskites

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• 作者：Andrei Buin ; Patrick Pietsch ; Jixian Xu ; Oleksandr Voznyy ; Alexander H. Ip ; Riccardo Comin ; Edward H. Sargent
• 刊名：Nano Letters
• 出版年：2014
• 出版时间：November 12, 2014
• 年：2014
• 卷：14
• 期：11
• 页码：6281-6286
• 全文大小：447K
• ISSN：1530-6992

文摘

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 卤 40 nm) diffusion length confirms this new picture of the importance of growth conditions.

Keywords:

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