Theoretical Analysis of the Effect of the Interfacial MoSe2 Layer in CIGS-Based Solar Cells

The aim of this work is to analyze the influence of the interfacial MoSe2 layer on the performance of a /n-ZnO/i-ZnO/n-Zn(O,S)/p-CIGS/p+-MoSe2/Mo/SLG solar cell. In this investigation, the numerical simulation software AFORS-HET is used to calculate the electrical characteristics of the cell with and without this MoSe2 layer. Different reported experimental works have highlighted the presence of a thin-film MoSe2 layer at the CIGS/Mo contact interface. Under a tunneling effect, this MoSe2 layer transforms the Schottky CIGS/Mo contact nature into a quasi-ohmic one. Owing to a heavily p-doping, the MoSe2 thin layer allows better transport of majority carrier, tunneling them from CIGS to Mo. Moreover, the bandgap of MoSe2 is wider than that of the CIGS absorbing layer, such that an electric field is generated close to the back surface. The presence of this electric field reduces carrier recombination at the interface. Under these conditions, we examined the performance of the cell with and without MoSe2 layer. When the thickness of the CIGS absorber is in the range from 3.5 μm down to 1.5 μm, the efficiency of the cell with a MoSe2 interfacial layer remains almost constant, about 24.6%, while that of the MoSe2-free solar cell decreases from 24.6% to 23.4%. Besides, a Schottky barrier height larger than 0.45 eV severely affects the fill factor and open circuit voltage of the solar cell with MoSe2 interface layer compared to the MoSe2-free solar cell.