Effect of interface recombination on solar cell parameters

A model is presented for p–n hetero-junction solar cells in which interface recombination is the dominant diode current transport mechanism. The model explains the large diode ideality factor (n>2) and the increased saturation current density in terms of increased density of interface states N_ir. Furthermore, the model allows us to explain the non-translation between illuminated and dark J–V characteristics. The explanation is based on the assumption that, for high interface state density values, both the depletion layer width and the diffusion voltage in the p- and n-side of the junction are functions of N_ir. The interface recombination leads to lower values of the open-circuit voltage, short-circuit current density, and fill factor. These results are illustrated by numerical calculations of solar cell parameters and compared with experimental data achieved for ZnO/CdS/CuGaSe₂ single-crystal solar cells.