Interfacial defect mediated charge carrier trapping and recombination dynamics in TiO2-based nanoheterojunctions

Abstract

The construction of heterojunctions is an effective strategy to prevent the charge carrier recombination. Owing to the lattice mismatch, it is unavoidable that many defects would be introduced at the heterojunction interface, thus developing a quantitative description on effect of interfacial defects on carrier dynamics become very imminent. In this paper, we employ ultrafast transient absorption (TA) and time resolved photoluminescence (TRPL) spectroscopy to investigate the interfacial defects related carrier trapping, separation, and recombination dynamics in WS2/TiO2 heterojunction. The results reveal the interfacial defects act as the carrier trapping center, and the trapping of electrons possesses active effect, while the co-trapping of both electrons and holes exhibits passive effect on charge carriers transition and separation. Accordingly, both the population and lifetime of carriers are accelerated substantially when only electrons are trapped, whereas the lifetime of charge carriers cannot be prolonged effectively when both electrons and holes are trapped. This work provides a detailed understanding of the interfacial defects mediated charge carrier trapping and recombination dynamics, providing a significant guidance for the future design of high-performance photoactive nanoheterojunctions.