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Title: Transformation of sintered CsPbBr3 nanocrystals to cubic CsPbI3 and gradient CsPbBrxI3–x through halide exchange

All-inorganic cesium lead halide (CsPbX3, X = Br, I) perovskites could potentially provide comparable photovoltaic performance with enhanced stability compared to organic–inorganic lead halide species. However, small-bandgap cubic CsPbI3 has been difficult to study due to challenges forming CsPbI3 in the cubic phase. Here, a low-temperature procedure to form cubic CsPbI3 has been developed through a halide exchange reaction using films of sintered CsPbBr3 nanocrystals. The reaction was found to be strongly dependent upon temperature, featuring an Arrhenius relationship. Additionally, film thickness played a significant role in determining internal film structure at intermediate reaction times. Thin films (50 nm) showed only a small distribution of CsPbBrxI3–x species, while thicker films (350 nm) exhibited much broader distributions. Furthermore, internal film structure was ordered, featuring a compositional gradient within film. Transient absorption spectroscopy showed the influence of halide exchange on the excited state of the material. In thicker films, charge carriers were rapidly transferred to iodide-rich regions near the film surface within the first several picoseconds after excitation. Furthermore, this ultrafast vectorial charge-transfer process illustrates the potential of utilizing compositional gradients to direct charge flow in perovskite-based photovoltaics.
Authors:
 [1] ;  [1] ;  [1]
  1. Univ. of Notre Dame, Notre Dame, IN (United States)
Publication Date:
Grant/Contract Number:
FC02-04ER15533
Type:
Published Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 27; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Notre Dame, Notre Dame, IN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1259934
Alternate Identifier(s):
OSTI ID: 1267221