Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. Carrier recombination at defects is detrimental to the device performance. While the bulk carrier parameters in the perovskites such as mobility and bulk carrier lifetime show sufficient characteristics, the surface carrier dynamics has not been studied. If not properly managed, surfaces can be a major source of carrier recombination. Separating surface carrier dynamics from bulk and/or grain-boundary recombination in thin films is challenging. Here, we use transient reflection spectroscopy to investigate the surface carrier dynamics in both methylammonium lead halide perovskite single crystals and polycrystalline films.1–2 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.
© 2017 Optical Society of AmericaPDF Article