Computational design of two-dimensional MX/MY (M = In, Ga, Al; X = S, Te; Y = P, Sb, As) heterojunctions with promising optoelectronic properties

Herein, the synergy of monolayer group III–V (MY, M = In, Ga, Al; Y = P, Sb, As) and III–VI (MX, M = In, Ga; X = S, Te) binary compounds is explored using first-principles simulations. Our results indicate that AlSb/InTe and InAs/InTe are direct-bandgap type-II heterojunctions with bandgaps of 0.54 and 0.61 eV, respectively. Compared to the two individual monolayers, the absorption spectra of the MX/MY heterojunctions exhibit a pronounced redshift and increased absorption coefficient. Especially in the near-infrared region (780–1400 nm), its optical absorption coefficient remains at a relatively high level, approximately 10⁵ cm⁻¹. Additionally, the application of biaxial in-plane strain effectively tunes the bandgap of these heterojunctions and extends their absorption spectra into the near-infrared range. Moreover, the charge transfer at the interface of MX/MY heterojunction reveals the characteristics of its direct type-II heterojunction. The InTe/AlSb heterojunction shows a high solar-to-hydrogen (STH) efficiency of 37.31 %, which suggesting promise for application in photocatalytic water decomposition. These findings reveal that MX/MY heterojunctions can be used for the design of high-performance optoelectronic devices.