Unraveling the Role of Interfacial Charge Transfer on Photoactivity and Anomalous Luminescence Quenching of V4C3Tx/Protonated g-C3N4 Heterostructures

Abstract

Two-dimensional van der Waals heterostructures with exotic quantum phenomena have garnered a huge surge in the field of optoelectronic devices. Herein, we report spectroscopic evidence of efficient interfacial charge transfers at the interface of a novel 2D/2D V4C3Tx MXene/protonated g-C3N4 (PCN) heterostructured thin film, demonstrating robust photosensitivity and a large exciton activation energy of 139.5 meV. Through temperature-dependent photoluminescence (PL) and time-resolved PL spectroscopy, we unravel the photophysical mechanism driving efficient charge transfer and photosensitivity in V4C3Tx/PCN heterostructures. These heterostructures exhibit superior photosensitivity to white and UV light compared with either PCN or V4C3Tx pristine materials. Additionally, we observed significant PL quenching with unusual negative thermal quenching and extended charge carrier lifetime in the V4C3Tx/PCN heterostructures across a broad temperature range of 70-370 K. Notably, at the elevated temperature of 370 K, the carrier lifetime was enhanced by more than 2-fold, making the heterostructures promising for optoelectronic applications. This work provides critical insight into the charge transfer mechanism between V4C3Tx MXene and PCN, opening a new avenue for rationally designing g-C3N4-based heterostructures for highly photosensitive optoelectronic devices.