Analytical modeling and optimization of original bifacial solar cells based on Cu(In,Ga)Se2 thin films absorbers

In this article, thin films CuGa0.3In0.7Se2 (CIGS) layers were grown onto soda lime glass (SLG) substrates and transparent conducting oxide (SnO2:F) using close-spaced vapor transport technique (CSVT). The details of the experimental results of the fabrication and characterization of the samples were presented. Then, these obtained results have been exploited to simulate the performances of ZnO:Al/iZnO/In2Se3/ODC/CIGS/SnO2:F/SLG bifacial solar cells structure using Analysis for Microelectronic and Photonic Structures (AMPS-1D). We show how the device performance is affected by the CIGS absorber parameters, especially thickness for the front and the back contact. The obtained results indicate that, at the back side illumination, the efficiency of the cell increased as the thickness of the CIGS absorber layer decreased. This was because the photo-generated carriers by the illumination of the rear face have difficulties to reach the junction, and the light is absorbed away from the junction and close to the back contact region. It is suggested that the p++ CuInSe2(CIS) thin layer was found to be a key factor to affect the solar cell performances. Combining two transparent contacts, achieved efficiencies of 16.3% and 14% were obtained with illumination from the front and the back contact, respectively.