Impact of the phase transition of halide perovskite on the performance of ZnO ultraviolet photoconductor.

Abstract

Despite the limitations associated with the delta-phase perovskite (δ-PVK), its potential to enhance device performance and stability has recently attracted increasing interest. In this work, we investigate the influence of these properties on the performance of ZnO-based ultraviolet (UV) photoconductors by surface-modifying the ZnO active layer with a δ-PVK layer derived from the phase transition of alpha-phase triple-cation mixed-halide perovskite, (Cs_0.05FA_0.81MA_0.14)Pb(I_0.85Br_0.15)₃ (α-PVK), via solution processing. The resulting ZnO/δ-PVK UV photoconductor exhibits enhanced performance, which is attributed to effective interfacial charge transfer from δ-PVK to ZnO, accompanied by an enhanced photogating effect. Compared with the ZnO device, the ZnO/δ-PVK device exhibits a photocurrent (I _photo) ca. 3 times higher, while being ca. 2 orders of magnitude higher than that of the ZnO/α-PVK device. Accordingly, the ZnO/δ-PVK device achieves the highest I _on/I _off ratio (344.81), photoresponsivity (R = 2.0 A W^-1), photodetectivity (D* = 3.06 × 10¹¹ Jones) and external quantum efficiency (EQE = 680%) under 365 nm UV irradiation at a power density (P) of 23 mW cm^-2 and a bias voltage of 1 V. These findings highlight the potential of the previously underexplored δ-PVK phase for enhancing the performance of optoelectronic devices.