Accurate determination of excitonic spectra of monolayer Selenium - PtS2 van der Waals heterostructure

The newly discovered monolayer selenium from group VI elements gains prominence due to its potential application in diverse fields including optoelectronics. In this work we have performed a systematic first principles study on the structural, electronic, linear and nonlinear optical characteristics of selenium Van der Waals (vdW) heterostructure with noble metal chalcogenide PtS2. The GW-Bethe-Salpeter Equation (GW-BSE) approach was used to accurately treat the quasiparticle and excitonic spectra. The optimized heterostructure shows the indirect band gap of 0.82 eV at GGA-PBE level. The newly designed interface shows type II band alignment. GW-BSE absorption spectra show a bound excitonic peak at 1.40 eV as compared with 1.28 eV in monolayer Se. The exciton binding energy of the Se-PtS2 vdW interface is 0.35 eV compared with the 0.45 eV for monolayer Se. The strong excitonic visible light absorption together with the type II band alignment makes the Se-PtS2 vdW heterostucture suitable candidate for the photovoltaic and photocatalytic applications.