Phenethylammonium cations induced (112)-Oriented MAPbI₃ single crystals for ultra-sensitive photodetection

The crystallographic orientation of perovskite single crystals (SCs) governs their charge transport properties and is therefore critical for optoelectronic applications. Despite extensive efforts, strategies for achieving perovskite SCs with high-index facets such as the (112) orientation remain largely unexplored, with most devices relying on the (100) or (001) facets. Here, we demonstrate that highly oriented methylammonium lead iodide (MAPbI₃) SCs exposing (112) facets can be synthesized by introducing phenethylammonium cations (PEA+) as a facet inducer during an in situ inverse temperature crystallization process. Using phenethylammonium chloride (PEACl) as the inducer, the SCs exhibit a hole mobility as high as 302 cm2 V−1 s−1. Lateral-structured photodetectors fabricated from these crystals achieve a responsivity of 228.7 A W−1 under 532 nm illumination. Notably, the specific detectivity reaches 6.8 × 1013 Jones, which is nearly one order of magnitude higher than that of the pure MAPbI₃ SC photodetectors. These results establish the (112) and (224) facets as key determinants of efficient charge transport in MAPbI₃ and, more broadly demonstrate that high-index facet engineering offers a previously untapped route for substantially enhancing the performance of perovskite optoelectronic devices.