Self-Powered Photodetectors Based on Core–Shell ZnO–Co₃O₄ Nanowire Heterojunctions

Abstract

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–Co3O4 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 Co3O4 films (in the range 1–15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al2O3 buffer layer between ZnO and Co3O4 was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO–Al2O3–Co3O4 system at zero bias is 6 times higher compared to that of ZnO–Co3O4. The responsivity (R) and specific detectivity (D*) of the best device were 21.80 mA W–1 and 4.12 × 1012 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.

Vertically aligned Co3O4 nanorods as a platform for inverted all‐oxide heterojunctions

“…Particularly, in the case of p‐on‐n core‐shell nanostructured heterojunction consisting of ZnO nanowires and Co 3 O 4 absorber shell, the fabricated cells resulted in poor PV performance with low V oc (max V oc in the order of tens of mV). [ 34 ] In this respect, while representing the ideal material in terms of E g to boost PCE in all‐oxide solar cells, Co 3 O 4 was the object of very limited studies, and no investigation can be found, in which it is applied as the core of an n‐on‐p inverted structure.…”

Photodetecting properties of single CuO–ZnO core–shell nanowires with p–n radial heterojunction

“…Thus, these radial core–shell heterostructure nanowires can be regarded as “smart materials” with controlled interfaces and enhanced multi-functionalities that can lead to the development of the next-generation high-performance optoelectronic devices 14 – 16 . Hence, radial core–shell nanowire arrays based on ZnO–Cu x O 16 , ZnO/CuCrO 2 17 , ZnO/WS 2 18 , ZnO–Cu 2 O 19 , ZnO–Co 3 O 4 20 , ZnO/ZnS 21 , CdSe/ZnTe 22 , etc. with applications in photodetectors have been reported.…”

A Self‐Powered High‐Performance UV Photodetector Based on Core–Shell GaN/MoO3–x Nanorod Array Heterojunction

“…The performance of recently developed self‐powered UV photodetectors (especially photodetectivity) is still unsuitable for practical applications due to energy loss or carrier recombination in the step of light absorption and photogenerated carrier transport. [ 16,17 ] Fabrication of low‐dimensional nanostructures is a promising approach to solve this issue. [ 9,18–20 ] Among different nanostructures, 1D nanoarray structure‐based photodetectors exhibit a series of advantages compared with their thin‐film counterparts.…”

“…[ 21,22 ] On the one hand, multiple reflection/scattering of incident light in 1D nanoarray materials can significantly increase the probability of light absorption. [ 16 ] On the other hand, 1D nanostructures with minimized charge‐carrier transport paths can reduce the transit time and effectively improve charge carrier separation. [ 23 ]…”

“…The core–shell structure exhibits faster carrier transfer and stronger light absorption compared with the film geometry. [ 16,37 ] The homogeneity and quality of MoO 3– x coating layers covered on GaN NRAs have been optimized. We have further elucidated the formation mechanism of nonstoichiometric MoO 3– x that is ascribed to the introduction of oxygen vacancies.…”