Optoelectronic Properties of MoS2 in Proximity to Carrier Selective Metal Oxides

Abstract

Transition metal dichalcogenides are an exciting class of new absorber materials for photovoltaic applications due to their unique optoelectronic properties in the single to few-layer regime. In recent years, these materials have been intensively studied, often utilizing conventional substrates such as sapphire and silicon dioxide on silicon. This study investigates the optical properties of molybdenum disulfide (MoS2) mono-, bi-, and multilayer films prepared by flake exfoliation and atomic layer deposition (ALD). These films are transferred to different photovoltaic relevant carrier-selective contacts, such as titanium oxide, titanium–titanium oxide, molybdenum oxide, and silicon–silicon dioxide reference substrates. Raman and photoluminescence (PL) spectra of single-crystalline exfoliated MoS2 flakes and ALD-grown MoS2 films on different substrates are compared in order to investigate the influence of the different contact materials on the corresponding optical transitions in MoS2. It is demonstrated that the different substrates influence the Raman and PL spectra of MoS2 layers due to doping and charge transfer effects, and similar effects are observed in both the exfoliated single-crystalline flakes and ALD-grown MoS2 layers.