Self‐Powered and Flexible Photodetector with High Polarization Sensitivity Based on MAPbBr₃–MAPbI₃ Microwire Lateral Heterojunction

Abstract Assembling perovskites into heterojunctions is an effective approach to achieve high‐performance photodetectors. Compared with vertical heterojunctions, in lateral heterojunction‐based photodetectors, the reflection loss is reduced because the active layer is in direct contact with light resulting in higher performance and better stability. However, lateral perovskite–perovskite heterojunctions are difficult to achieve using solution methods because the first formed film is easily dissolved by the solvent of the second precursor. In this study, a two‐step imprinting method is developed to fabricate lateral MAPbI₃–MAPbBr₃ microwire heterojunctions and realize a high‐performance photodetector with a responsivity and detectivity of 1207 A W⁻¹ and 2.78 × 10¹³ Jones, respectively. At 0 V bias, the device exhibits a responsivity of up to 233 A W⁻¹, which is more than double the previously reported best results. The high‐quality heterojunction endows the photodetectors with ultra‐high polarization sensitivity (I_max/I_min = 8.2) and long‐term stability, retaining 88.2% of its initial performance even after being exposed to air for 391 d.