Interfacial study of vertically aligned n-type MoS2 flakes heterojunction with p-type Cu-Zn-Sn-S for self-powered, fast and high performance broadband photodetector

Abstract

The p-n junction is an influential trait for efficient charge transport in electronic and optoelectronic devices. Demonstrating p-n junction using 2D TMDCs is inescapable to integrate these materials with matured 3D material technology, as 2D material offers easy integration due to the absence of dangling bonds. However, understanding the electronic properties at the interface is crucial for rational design of heterojunction devices for their novel and unmatched functionality. Present work reports detail interfacial study and band-alignment of two potential materials, 3D Cu2ZnSnS4(CZTS) and 2D-layered MoS2. The detail photoelectron spectroscopy measured the valance band offset (VBO) and conduction band offset (CBO) of −0.23 ± 0.1 eV and −0.29 ± 0.1 eV, respectively and established a favorable type-II band-alignment at CZTS/MoS2 interface. Significant PL quenching at CZTS/MoS2 interface proven to be strong evidence of efficient charge transport. As a proof of concept, a self-driven CZTS/MoS2 heterojunction broadband photodetector was constructed exhibiting pronounced photovoltaic features with high responsivity 141 mA/W, outstanding photoswitching capability (IOn/IOff = 112) and fast response (τr/τd = 81/79 ms). The responsivity was further enhanced to 79A/W at moderate bias (@6V). Additionally, the device showed exceptional stability after 1500 h of operation. This work intends to trigger the research on 3D/2D for high performing optoelectronic devices based on CZTS/MoS2 heterojunctions.