A study of 2H and 1T phases of Janus monolayers and their van der Waals heterostructure with black phosphorene for optoelectronic and thermoelectric applications

Abstract

Pristine Janus monolayers (MXY; M ​= ​Mo, W and X/Y = S, Se, Te) in 2H and 1T phases and their corresponding vdW heterostructures with black phosphorene are studied under density functional theory calculations. Phonon spectrum confirms dynamic stability of all monolayers in both patterns except MoSSe, WSSe, WSeTe and WSTe in 1T layout. Direct energy gap is observed for MoSSe, MoSeTe, WSSe, and WSeTe in 2H arrangement. In 1T phase, MoSSe, WSSe and their respective heterostructures exhibit metallic attributes and are suitable for high speed supercapacitors. Remnant heterostructures are indirect band gap semiconductors in both phases. PDOS affirms type-I band alignment of BlackP-MoSSe and BlackP-MoSeTe in 2H and BlackP-WSTe in 1T phase that can be well employed for future IR detectors. Moreover, globally desirable type-II band association is investigated for remaining heterostructures rendering exclusive laser, optoelectronic, photovoltaic and sensing applications. Each system manifests incredible effective masses of charge carriers. Heterostructures present a significant potential drop and work function (Φ). Also, every single heterostructure demonstrates noteworthy charge transfer which is accountable for electrostatic as well as vdW interaction at interface. Furthermore, sophisticated optical properties of all heterostructures are achieved by estimating absorption spectra. Optical responses suggest their eminent optoelectronic device applications like: telecommunication laser, optical fiber, photo diodes and solar cells. In addition, a comprehensive insight into thermoelectric properties of all the systems illustrates their ability for thermoelectric generator. Likewise, these materials are suitable alternative for non-toxic and inexpensive thermoelectric devices for waste heat recovery at ambient temperature.