Experimental and theoretical study on the role of 2D Ti3C2Tx MXenes on superior charge transport and ultra-broadband photodetection in MXene/Bi2S3 nanorod composite through local Schottky junctions

Abstract

2D MXenes have garnered widespread attention in the fields of photocatalysis, energy conversion etc. because of their unique properties. Integration of semiconductor nanostructures with 2D MXene can be a promising approach for high-performance photodetection. Herein, we adopted an in-situ hydrothermal approach for in-situ anchoring of Ti3C2Tx MXene nanosheets on 1D Bi2S3 nanorods and fabricated a Bi2S3/Ti3C2Tx (1D/2D) Schottky junction broadband photodetector (PD) with outstanding performance. The mechanism behind the excellent performance and formation of the local Schottky junction was investigated through density functional theory (DFT) calculations and validated through various microscopic and spectroscopic tools. In particular, the DFT analysis reveals that the partial density of states of Bi2S3 is altered with additional electronic states in the band-gap region due to attachment of Ti3C2O2, which helps in the efficient charge transport and charge separation across the local junctions. Ultraviolet photoelectron spectroscopy elucidates the nature of band alignment and interfacial charge transfer across the Bi2S3/Ti3C2Tx MXene junction locally. The low-cost PD exhibits an excellent broadband responsivity spanning from ultraviolet to near-infrared region (300–1550 nm) with a peak responsivity of 36.7 A/W and 26.2 A/W at 300 nm and 780 nm, respectively. Further, the device exhibited an external quantum efficiency of ∼3.9 × 103 %, and a fast response of ∼300 μs under 3 V bias, which are remarkable. Finally, the fabricated PD demonstrates a very high long-term storage stability in ambient condition. This work provides a deeper insight into the superior charge transport and ultra-broadband photodetection in MXenes based composites for high-performance optoelectronic applications.