Prediction of high photoconversion efficiency and photocatalytic water splitting in vertically stacked TMD heterojunctions MX2/WS2 and MX2/MoSe2 (M = Cr, Mo, W; X = S, Se, Te)†

Abstract

Based on two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibiting strong light–matter interactions and spin-valley locking properties, we construct two types of MX₂/WS₂ and MX₂/MoSe₂ (M = Cr, Mo, W, and X = S, Se, Te) heterojunctions to investigate their electronic and optical properties based on first principles calculations. The calculated results indicate that eight heterojunctions are semiconductors with staggered gaps, which are beneficial for prolonging the lifetime of excitons and promoting the efficient separation of photogenerated electrons and holes. The absorption coefficients of these heterojunctions reach the order of 10⁵ cm⁻¹ in the visible range, especially the MX₂/MoSe₂ heterojunctions. Among the considered heterojunctions, MoS₂/WS₂, MoSe₂/WS₂, WSe₂/WS₂, and WSe₂/MoSe₂ heterojunctions exhibit suitable band gaps and high carrier mobility, indicating promising potential for photocatalysis. Meanwhile, a promising water splitting photocatalyst WSe₂/MoSe₂ is predicted successfully by analyzing the corresponding photocatalytic water splitting properties. More importantly, the photoconversion efficiency (PCE) of the MoTe₂/MoSe₂ heterojunction is as high as 25.84%, which is a larger value compared to the PCE of the OsNCl/FeNCl heterojunction (23.45%) reported recently. These findings provide theoretical evidence and identify excellent candidate materials for the advancement of optoelectronics and photocatalysis.