Stable α-CsPbI₃ perovskite nanowire arrays with preferential crystallographic orientation for highly sensitive photodetectors

All-inorganic metal-halide perovskites CsPbX ₃ (X = Cl, Br, I) exhibit higher stability than their organic–inorganic hybrid counterparts, but the thermodynamically instable perovskite α phase at room temperature of CsPbI ₃ restricts the practical optoelectronic applications. Although the stabilization of α-CsPbI ₃ polycrystalline thin films is extensively studied, the creation of highly crystalline micro/nanostructures of α-CsPbI ₃ with large grain size and suppressed grain boundary remains challenging, which impedes the implementations of α-CsPbI ₃ for lateral devices, such as photoconductor-type photodetectors. In this work, stable α-CsPbI ₃ 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.