Investigation of the Effect of Substrate Thickness on Absorption of TMDC Monolayers in the Visible Wavelength

Two-dimensionam transition-metal dichalcogenides (TMDC) layers with direct bandgaps have made a new horizon for application in photonics and electroptics. The presence of bandgap causes a significant absorption useful in photovoltaic devices. When these layers are located on a substrate that leads to a frequent optical reflection thus affect the absorption. Typically, SiO2 or Si or their combination as a substrate is used for these monolayers. In this paper, we used a transfer matrix method to study the absorption spectra of TMDC monolayers including MoSe2, WSe2, MoS2 and WS2 with the presence of SiO2/ Si substrate with different thicknesses of SiO2 layer. We found that using the SiO2 layer with a thickness of 90 nm in SiO2/ Si substrate does not change the general behavior of absorption and increases the absorption in some regions of the wavelength range.