Unraveling the Roleof Interfacial Charge Transferon Photoactivity and Anomalous Luminescence Quenching of V₄C₃T<i>_<i>x</i></i>/Protonatedg‑C₃N₄ Heterostructures

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 V₄C₃T<i>_<i>x</i></i> 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 V₄C₃T<i>_<i>x</i></i>/PCN heterostructures. These heterostructures exhibit superior photosensitivity to white and UV light compared with either PCN or V₄C₃T<i>_<i>x</i></i> pristine materials. Additionally, we observed significant PL quenching with unusual negative thermal quenching and extended charge carrier lifetime in the V₄C₃T<i>_<i>x</i></i>/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 V₄C₃T<i>_<i>x</i></i> MXene and PCN, opening a new avenue for rationally designing g-C₃N₄-based heterostructures for highly photosensitive optoelectronic devices.