Stable and ultraviolet-enhanced broadband photodetectors based on Si nanowire arrays-Cs3Cu2I5 nanocrystals hybrid structures

Abstract

Silicon has been the most widely used material for broadband photodetectors. However, the weak response in ultraviolet (UV), especially in deep-UV region, and the large dark current are still their critical drawbacks for practical applications. In this study, a strategy of decorating Cs3Cu2I5 nanocrystals (NCs) on Si nanowire arrays (NWAs) to form a hybrid structure was proposed to overcome the above two issues. Because of the wide and direct bandgap of Cs3Cu2I5 with intrinsic UV light absorption, the photodetection ability of the hybrid detector in UV region was substantially enhanced owing to the efficient down-conversion of the UV incident light. Moreover, driven by a designed Schottky junction from asymmetric electrodes, the hybrid detector can be operated without external power supply. Typically, at 265 nm light excitation, the Si NWA-Cs3Cu2I5 NCs hybrid device achieved a high photoresponsivity of 83.6 mA W−1, a specific detectivity of 2.1 × 1012 Jones, and a large on/off ratio of 3.72 × 103 at 0 V, nearly 350 times higher than the bare Si NWA device. More importantly, the unencapsulated photodetector demonstrates an outstanding operational stability over the aging test for 10 h, and can endure a high humidity (75%, 7 days) and a long-term storage for 300 days in air ambient. Since the different deep-UV light sensitivity of the devices modified with/without Cs3Cu2I5 NCs, a monolithically deep-UV light recognition system was therefore fabricated. It is anticipated that the present strategy provides a new avenue for the preparation of UV-enhanced broadband photodetectors, opening up opportunities for development of integrated optoelectronic systems in the future.