Eur. Phys. J. B (2012) 85: 392
https://doi.org/10.1140/epjb/e2012-30449-7

Regular Article

Optical and photocatalytic properties of two-dimensional MoS₂

¹ Physical Science & Engineering Division, KAUST, 23955-6900 Thuwal, Kingdom of Saudi Arabia
² Solar and Photovoltaic Energy Research Center (SPERC), KAUST, 23955-6900 Thuwal, Kingdom of Saudi Arabia

^a e-mail: udo.schwingenschlogl@kaust.edu.sa

Received: 6 June 2012
Received in final form: 31 August 2012
Published online: 29 November 2012

Abstract

The electronic structure and optical spectrum of monolayer MoS₂ are calculated using both the modified Becke-Johnson (mBJ) approximation and Bethe-Salpeter equation. Bulk MoS₂ is an indirect band gap semiconductor, but thinned to a monolayer it converts to a direct band gap semiconductor with increased gap. The calculated mBJ band gaps of MoS₂ amount to 1.15 eV for the bulk and 1.90 eV for the monolayer, in excellent agreement with experiment. The experimental excitonic peaks of monolayer MoS₂ at 1.88 eV and 2.06 eV are reproduced by the calculations. The high photoluminescence yield can be attributed to a high binding energy of the excitons and is not due to a splitting of the valence bands, as is commonly assumed. We also show that monolayer MoS₂ has the ability to oxidize H₂O and produce O₂ as well as to reduce H⁺ to H₂.