Ultrahigh quantum efficiency photodetector and ultrafast reversible surface wettability transition of square In₂O₃ nanowires

Due to a large surface-to-volume ratio, the optoelectronic performance of lowdimensional semiconductor nanostructure-based photodetectors depends in principle on chemisorption/photodesorption at the exposed surface, but practical examples that show such an effect are still unavailable. Some theoretical calculations have predicted that the {001} facets of In₂O₃ can effectively accumulate photogenerated holes under irradiation, providing a model material to examine whether the facet cutting of nanowires (NWs) can boost their optoelectronic performance. Herein, we present the design and construction of a novel nanowire-based photodetector using square In₂O₃ NWs with four exposed {001} crystal facets. The photodetector delivers excellent optoelectronic performance with excellent repeatability, fast response speed, high spectral responsivity (R_λ), and high external quantum efficiency (EQE). The R_λ and EQE values are as high as 4.8 × 10⁶ A/W and 1.46 × 10⁹%, respectively, which are larger than those of other popular semiconductor photodetectors. In addition, the square In₂O₃ NWs show hydrophobic wettability as manifested by a contact angle of 118° and a fast photoinduced reversible switching behavior is observed.