Journal
NANO LETTERS
Volume 14, Issue 11, Pages 6281-6286Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl502612m
Keywords
Perovskite; defect; electronic traps; diffusion length; growth; precurson
Categories
Funding
- King Abdullah University of Science and Technology (KAUST) [KUS-11-009-21]
- Ontario Research Fund Research Excellence Program
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- Ontario Government
- Canada Foundation for Innovation under the Compute Canada
- Government of Ontario
- Ontario Research Fund-Research Excellence
- University of Toronto
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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.
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