Tunable surface band bending enables switchable photoconductance of colloidal InSb nanowires for self-powered and broadband photodetectors with fast response

Switchable photodetection from positive photoconductance (PPC) to negative photoconductance (NPC) is significant for constructing next-generation optoelectronics such as optical device switching, weak signal detection, and photoresponsive memories. Nevertheless, the difficult operability, restricted performance and intricate mechanism have impeded its practical implementation. In this study, an in-situ convenient calcination strategy is conducted to achieve inverse photoconductance in colloidal InSb nanowires (NWs)-based photodetectors. The surface of the as-calcined InSb NWs is demonstrated to be composed of thicker oxide shells with anchored In 2 O 3 nanoparticles compared to that of the pristine InSb NWs, which only consist of thin amorphous native oxide shells. Mechanism studies indicate that the surface chemical states can serve as surface trapping states as well as scattering centers, which can trigger the higher surface band bending and reduce the density and mobility of free carriers, thus lowering the photoconductivity below in dark condition, leading to NPC. It is noteworthy that the PPC and NPC-dominated photodetectors exhibit rapid photoresponse rise and decline times at zero bias voltage under light illumination from 405 to 980 nm. This work offers certain guidance for the modulation of surface chemical states and their associated effects, which can be employed in the development of future optoelectronic applications.