Analysis of illumination-intensity-dependent j–V characteristics of ZnO/CdS/CuGaSe2 single crystal solar cells

Current–voltage characteristics of ZnO/CdS/CuGaSe2 single crystal solar cells measured at room temperature are investigated depending on illumination intensity. The characteristics can be described using the two-diode model, indicating two current transport mechanisms acting in the cells. The first and dominant mechanism is recombination of carriers at the interface between CdS and CuGaSe2. The second one is recombination in the depletion region, which has been found to have a small effect on the solar cell photovoltaic performance. Both the diode ideality factor and the saturation current density of the dominant diode increase under illumination. A model based on interface recombination can explain these results. This model allows the estimation of diffusion voltage, capture cross-section of holes at the interface and mobility of electrons in the CdS layer.