Impact of in-plane electric field on the optical properties of CO₂ adsorbed 2D MoSe₂ monolayer: application as a photodetector

We present the results of an investigation of the optical characteristics of pristine and CO₂-adsorbed MoSe₂ monolayers with (without) an external electric field. The optical parameters of interest are the absorption coefficient (α), reflectance (R_f), refractive index (n), and photoconductivity (σ). The impact of an external electric field (−2 × 10⁸ V/cm) on the optical behavior of the MoSe₂ monolayer is systematically investigated. The results show the peaks of the real component (\(\varepsilon_{1}\)) of the dielectric function for both pristine and CO₂-adsorbed MoSe₂ monolayers in the energy range of 2–3 eV. The imaginary part (\(\varepsilon_{2}\)) of the dielectric function exhibits a shift toward the visible region from the ultraviolet (UV) region, in which CO₂ is adsorbed, and this shift increases toward the visible region with the application of an external electric field. Analysis of the absorption index, refractive index, and reflectance reveals that the peaks are aligned in the visible range for both the pristine MoSe₂ and CO₂-adsorbed MoSe₂ monolayers, with (without) an external electric field. The shifts of these peaks follow a similar trend as the imaginary part of the dielectric constant. Lastly, this study provides additional insight into the photo-detection performance parameters (internal quantum efficiency [IQE], external quantum efficiency [EQE], light extraction efficiency [LEE], and responsivity) for both pristine and CO₂-adsorbed MoSe₂ monolayers, considering the presence or absence of an external field.