Multilayer WSe₂/ZnO heterojunctions for self-powered, broadband, and high-speed photodetectors

Abstract

Self-powered broadband photodetectors have attracted great interest due to their applications in biomedical imaging, integrated circuits, wireless communication systems, and optical switches. Recently, significant research is being carried out to develop high-performance self-powered photodetectors based on thin 2D materials and their heterostructures due to their unique optoelectronic properties. Herein, a vertical heterostructure based on p-type 2D WSe₂and n-type thin film ZnO is realized for photodetectors with a broadband response in the wavelength range of 300-850 nm. Due to the formation of a built-in electric field at the WSe₂/ZnO interface and the photovoltaic effect, this structure exhibits a rectifying behavior with a maximum photoresponsivity and detectivity of ∼131 mA W^-1and ∼3.92 × 10¹⁰Jones, respectively, under an incident light wavelength of<i>λ</i>= 300 nm at zero voltage bias. It also shows a 3-dB cut-off frequency of ∼300 Hz along with a fast response time of ∼496<i>μ</i>s, making it suitable for high-speed self-powered optoelectronic applications. Furthermore, the facilitation of charge collection under reverse voltage bias results in a photoresponsivity as high as ∼7160 mA W^-1and a large detectivity of ∼1.18 × 10¹¹Jones at a bias voltage of -5 V. Hence, the p-WSe₂/n-ZnO heterojunction is proposed as an excellent candidate for high-performance, self-powered, and broadband photodetectors.