Optimized Cu2O/C-Si Tandem Heterojunction Solar Cells: Experimental and Modeling Investigation for Defect Analysis

Abstract

The photovoltaic (PV) market is dominated in present by crystalline silicon solar cells (more than 90%). Cost reduction of this technology could be obtained by promoting silicon –based tandem solar cells with low cost metal oxide materials. Cuprous oxide (Cu2O) is considered an attractive material for PV applications since it is a p-type semiconductor with high optical absorption and a direct bandgap of about 2.1 eV. The electrical and optical characteristics for aluminium doped ZnO (AZO) and undoped Cu2O thin film layers synthesized by magnetron sputtering were determined. A four-terminal AZO-Cu2O/ c-Si tandem heterojunction solar cell was investigated. I-V curve for the studied heterojunction tandem solar cell shows a rectifying behavior, but its stability and reproducibility has to be solved. Numerical modelling allowed to analyse the main electrical parameters of the two subcells, in order to maximize the performance of the solar device. The influence of the material characteristics of the buffer layer (electron mobility, buffer layer thickness and electron affinity) on the energy performance of the cell (η, FF, Jsc, VOC) was analyzed.The effect of interface defects on the electrical characteristics of the AZO/Cu2O heterojunction was evaluated. The defect analysis based on numerical modeling showed how the interface defects and band offsets of the considered Cu2O heterojunction tandem solar cell reduce top cell performance. The analysis suggested that the incorporation of a buffer layer could enhance the performance of the heterojunction solar cell.