A high-performance WS2/ZnO QD heterojunction photodetector with charge and energy transfer

Abstract

Two-dimensional/zero-dimensional (2D/0D) van der Waals heterojunctions have become a research hotspot for novel optoelectronic devices by virtue of their high light absorption and fast transportation. In previous studies, researchers preferred to construct heterojunctions with more matched energy bands to obtain high-performance photodetectors with efficient charge transfer. However, due to the limited configuration of 2D/0D heterojunctions, the coexistence mechanism of charge transfer and energy transfer has rarely been reported. In this work, we proposed a method to deliberately manipulate the defect states of ZnO quantum dots (QDs), which can achieve type-II band alignment and dipole–dipole interactions in the demonstrated WS₂/ZnO heterojunction system. The coexistence of mechanisms is confirmed by photoluminescence (PL) and time-resolved photoluminescence (TRPL). As a result, the photodetector exhibits a high-responsivity (R) of 1120 A W⁻¹ and a high-detectivity (D*) of 3.23 × 10¹² Jones. Moreover, the device reaches an ultra-fast response speed of 15 ns, which is one of the fastest response speeds of the current 2D/0D heterojunction photodetectors. The high photoresponse is attributed to the efficient interfacial carrier dynamics. Our work provides a new avenue for the coexistence of multiple mechanisms in 2D/0D heterojunctions, which is beneficial for the development of high-performance optoelectronic devices.