Benefit of Grain Boundaries in Organic–Inorganic Halide Planar Perovskite Solar Cells

The past 2 years have seen the uniquely rapid emergence of a new class of solar cell based on mixed organic–inorganic halide perovskite. Grain boundaries are present in polycrystalline thin film solar cell, and they play an important role that could be benign or detrimental to solar-cell performance. Here we present efficient charge separation and collection at the grain boundaries measured by KPFM and c-AFM in CH₃NH₃PbI₃ film in a CH₃NH₃PbI₃/TiO₂/FTO/glass heterojunction structure. We observe the presence of a potential barrier along the grain boundaries under dark conditions and higher photovoltage along the grain boundaries compare to grain interior under the illumination. Also, c-AFM measurement presents higher short-circuit current collection near grain boundaries, confirming the beneficial roles grain boundaries play in collecting carriers efficiently