Halide perovskites have shown great potential for light emission and photovoltaic applications due to their remarkable electronic properties. Although the device performances are promising, they are still limited by microscale heterogeneities in their photophysical properties. Here, we study the impact of these heterogeneities on the diffusion of charge carriers, which are processes crucial for efficient collection of charges in light-harvesting devices. A photoluminescence tomography technique is developed in a confocal microscope using one- A nd two-photon excitation to distinguish between local surface and bulk diffusion of charge carriers in methylammonium lead bromide single crystals. We observe a large dispersion of local diffusion coefficients with values between 0.3 and 2 cm2·s-1 depending on the trap density and the morphological environment- A distribution that would be missed from analogous macroscopic or surface measurements. This work reveals a new framework to understand diffusion pathways, which are extremely sensitive to local properties and buried defects.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: A.A.Z. and O.M.B. gratefully acknowledge the funding support from King Abdullah University of Science and Technology (KAUST). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. C.S. thanks the EPSRC (Nano-Doctoral Training Centre), the Cambridge Trust, and a Winton Graduate
Exchange Scholarship for funding. This project has received funding from the European Research Council (ERC) underthe European Union’s Horizon 2020 research and innovation programme (Grant Agreement Number 756962). S.D.S. acknowledges support from the Royal Society and Tata Group (UF150033). G.D. acknowledges the Royal Society for funding through a Newton International Fellowship. M.A. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No.841386. The authors thank the EPSRC for funding