Stable WSeTe/PtTe2 van der Waals heterojunction: Excellent mechanical, electronic, and optical properties and device applications

Janus WSeTe and PtTe2 monolayers have attracted much attention due to their outstanding electronic properties. To explore their combined advantages and to find new physics, we construct WSeTe/PtTe2 vdW heterojunctions and use the most stable configurations A4 and B1 to explore their various physical properties and device applications. It is found that both A4 and B1 hold exceptional mechanical properties. They are type-II semiconductors, and types of band alignment and band gap size can be tuned flexibly by external electric field and vertical strain. Based on such a property, we design a strain-controlled high on-off-ratio mechanical switching device. They also show an excellent light response and high photoelectric power conversion efficiency (PCE), which can be tuned greatly by the external electric field and vertical strain as well. For example, light adsorption in visible and infrared region can be improved greatly by the compressive strain. Particularly, we find for B1 in the intrinsic state or with a small tensile strain of 0.3 & Aring;, or for A4 with small electric field of -0.3 V/& Aring;, they all hold type-II band alignment and have very high PCE and large visible light absorption, based on these results, we propose high-performance solar cell devices.