Mixed halide lead perovskites (e.g., CH3NH3PbBrxI3-x) undergo phase segregation creating iodide-rich and bromide-rich domains when subjected to visible irradiation. This intriguing aspect of halide ion movement in mixed halide films is now being tracked through excited-state behavior using emission and transient absorption spectroscopy tools. These transient experiments have allowed us to establish the time scale with which such separation occurs under laser irradiation (405 nm, 25 mW/cm2 to 1.7 W/cm2) as well as dark recovery. While the phase separation occurs with a rate constant of 0.1-0.3 s-1, the recovery occurs over a time period of several minutes to an hour. The relative photoluminescence quantum yield observed for Br-rich regions (em. max 530 nm) is nearly 2 orders of magnitude lower than that of I-rich regions (em. max 760 nm) and arises from the fact that I-rich regions serve as sinks for photogenerated charge carriers. Understanding such cascading charge transfer to localized sites could further enable the design of gradient halide structures in mixed halide systems.
|Original language||English (US)|
|Number of pages||7|
|Journal||ACS Energy Letters|
|State||Published - Jun 20 2016|
Bibliographical noteKAUST Repository Item: Exported on 2022-06-03
Acknowledged KAUST grant number(s): OCRF-2014-CRG3-2268
Acknowledgements: We acknowledge ND Energy, University of Notre Dame for the seed funding of the project. P.V.K. and M.K. acknowledge the support of the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, through Award DE-FC02-04ER15533 and DE-SC0014334. J.S.M. acknowledges the support of King Abdullah University of Science and Technology (KAUST) through the Award OCRF-2014-CRG3-2268. This is contribution number NDRL No. 5123 from the Notre Dame Radiation Laboratory. We thank Dr. Donghoon Han for his assistance with AFM measurements and Mr. Weixin Huang for X-ray photoelectron spectroscopic characterization.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.