Electro-Optical Analysis and Numerical Modeling of Cu2O as the Absorber Layer in Advanced Solar Cells

Abstract

Solar cells in tandem with metal-oxide heterojunctions are interesting from a development standpoint for the next step beyond silicon performance limitations in high-efficiency solar cells. High optical absorptance makes copper oxide a prospective absorber layer. This work is constituted as an overview on the original work of the authors, based on experimental analysis of the copper oxide absorber layer and numerical modeling of its electro-optical characteristics. Copper oxide films were synthesized by RF/DC magnetron sputtering on quartz substrates. The electro-optical and structural characteristics of the layer incorporating metal oxides have been investigated using SEM (Scanning Electron Microscopy), SFM (Scanning Force Microscopy), Hall effect measurements, Fourier-transform infrared spectroscopy (FTIR) and spectrofluorometry. The SEM analysis shows an increase of the grain size in the sample treated with rapid thermal annealing at 900 °C. SFM analysis shows that thermal annealing increases the surface roughness by a factor of 10. FTIR spectra show cupric oxide peaks from oxidation of the copper oxide at the quartz. A Silvaco Atlas model was implemented in order to study the electrical parameters of a metal-oxide heterojunction with Cu2O and AZO, mainly studying the effect of a buffer layer in the heterojunction structure, as well as varying the layer thickness, the doping level and the defect density for several materials in the structure. The OPAL 2 simulation platform was deployed to model the optical parameters of the heterojunction structure, including the reflectance, transmittance and absorptance.