Carrier recombination at defects is detrimental to the performance of solar energy conversion systems, including solar cells and photoelectrochemical devices. Point defects are localized within the bulk crystal while extended defects occur at surfaces and grain boundaries. If not properly managed, surfaces can be a large source of carrier recombination. Separating surface carrier dynamics from bulk and/or grain-boundary recombination in thin films is challenging. Here, we employ transient reflection spectroscopy to measure the surface carrier dynamics in methylammonium lead iodide perovskite polycrystalline films. We find that surface recombination limits the total carrier lifetime in perovskite polycrystalline thin films, meaning that recombination inside grains and/or at grain boundaries is less important than top and bottom surface recombination. The surface recombination velocity in polycrystalline films is nearly an order of magnitude smaller than that in single crystals, possibly due to unintended surface passivation of the films during synthesis.
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K.Z. and M.Y. acknowledge the support by the hybrid perovskite solar cell programme of the National Center for Photovoltaics funded by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office. D.T.M. acknowledges the National Renewable Energy Laboratory Director’s Fellowship. Y.Yang, E.M.M. and M.C.B. acknowledge support from the Solar Photochemistry programme within the US. DOE, Office of Basic Sciences, Office of Science. Work at NREL was conducted under contract number DE-AC36-08G028308.
The authors declare no competing financial interests.
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Yang, Y., Yang, M., Moore, D. et al. Top and bottom surfaces limit carrier lifetime in lead iodide perovskite films. Nat Energy 2, 16207 (2017). https://doi.org/10.1038/nenergy.2016.207
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