Self-Powered Photodetectors Based on Core–Shell ZnO–Co<sub>3</sub>O<sub>4</sub> Nanowire Heterojunctions GhamgosarPedram RigoniFederica KohanMojtaba Gilzad YouShujie MoralesEdgar Abarca MazzaroRaffaello MorandiVittorio AlmqvistNils ConcinaIsabella VomieroAlberto 2019 Self-powered photodetectors operating in the UV–visible–NIR window made of environmentally friendly, earth abundant, and cheap materials are appealing systems to exploit natural solar radiation without external power sources. In this study, we propose a new p–n junction nanostructure, based on a ZnO–Co<sub>3</sub>O<sub>4</sub> core–shell nanowire (NW) system, with a suitable electronic band structure and improved light absorption, charge transport, and charge collection, to build an efficient UV–visible–NIR p–n heterojunction photodetector. Ultrathin Co<sub>3</sub>O<sub>4</sub> films (in the range 1–15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al<sub>2</sub>O<sub>3</sub> buffer layer between ZnO and Co<sub>3</sub>O<sub>4</sub> was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO–Al<sub>2</sub>O<sub>3</sub>–Co<sub>3</sub>O<sub>4</sub> system at zero bias is 6 times higher compared to that of ZnO–Co<sub>3</sub>O<sub>4</sub>. The responsivity (<i>R</i>) and specific detectivity (<i>D</i>*) of the best device were 21.80 mA W<sup>–1</sup> and 4.12 × 10<sup>12</sup> Jones, respectively. These results suggest a novel p–n junction structure to develop all-oxide UV–vis photodetectors based on stable, nontoxic, low-cost materials.