Stable α‐CsPbI3 Perovskite Nanowire Arrays with Preferential Crystallographic Orientation for Highly Sensitive Photodetectors

All‐inorganic metal‐halide perovskites CsPbX3 (X = Cl, Br, I) exhibit higher stability than their organic–inorganic hybrid counterparts, but the thermodynamically instable perovskite α phase at room temperature of CsPbI3 restricts the practical optoelectronic applications. Although the stabilization of α‐CsPbI3 polycrystalline thin films is extensively studied, the creation of highly crystalline micro/nanostructures of α‐CsPbI3 with large grain size and suppressed grain boundary remains challenging, which impedes the implementations of α‐CsPbI3 for lateral devices, such as photoconductor‐type photodetectors. In this work, stable α‐CsPbI3 perovskite nanowire arrays are demonstrated with large grain size, high crystallinity, regulated alignment, and position by controlling the dewetting dynamics of precursor solution on an asymmetric‐wettability topographical template. The correlation between the higher photoluminescence (PL) intensity and longer PL lifetime indicates the nanowires exhibit stable α phase and suppressed trap density. The preferential (100) orientation is characterized by discrete diffraction spots in grazing incidence wide‐angle scattering patterns, suggesting the long‐range crystallographic order of these nanowires. Based on these high‐quality nanowire arrays, highly sensitive photodetectors are realized with a responsivity of 1294 A W−1 and long‐term stability with 90% performance retention after 30‐day ambient storage. Stable α‐CsPbI3 nanowire arrays with high crystallinity, large grain size, and preferential crystallographic orientation are demonstrated on an asymmetric‐wettability topographical template. The suppressed grain boundary and surface trap of these nanowires are reflected by longer photoluminescence lifetime and long‐range crystallographic alignment. These high‐quality nanowires exhibit highly sensitive photodetection with responsivity of 1294 A W−1 and long‐term stability.