Unraveling interfacial interactions in reduced Nb2CTx/GO heterostructures for highly stable and transparent narrow-band photoelectrochemical photodetectors.

The rapid advancement of nanomaterial-based thin-film processing has significantly contributed to the development of multifunctional optoelectronic devices. Among novel nanomaterials, MXenes, 2D transition metal carbides, nitrides, and carbonitrides have garnered substantial attention due to their high optical transparency, tunable optical properties, and excellent electrochemical performance. In particular, niobium carbide (Nb₂CT_x) MXene holds great promise for photoelectrochemical photodetectors (PEC PDs) due to its narrow-band photodetection capability, solution-processing, and stability under light irradiation. However, current Nb₂CT_x-based and 2D-based PEC PDs, in general, suffer from low photocurrent density, limited optical transparency, and poor environmental stability, hindering their practical applications. In this study, we developed a polymeric binder-free transparent reduced Nb₂CT_x/graphene oxide (r-Nb₂CT_x/GO) heterostructured thin film using a facile layer-by-layer technique. Incorporating reduced GO not only assists in improving the electrical conductivity of the heterostructure but also serves as a binder for MXene flakes. We systematically investigate the physicochemical properties of the film, its photodetection, and electrochemical performance. The optimized film exhibits outstanding transparency (70% at 550 nm), narrow-band photodetection response in the ultraviolet region, an excellent photoresponsivity of 50.21 μA W^-1, and high environmental stability. Altogether, this study paves the way for developing Nb₂CT_x-based heterostructures for highly sensitive and environmentally stable transparent PEC PDs.