Evaluation of the photo-generated carrier density of GaAs solar cells by using electrical and optical biased electroreflectance spectroscopy

In this work, to investigate the optical and the electrical properties of GaAs solar cells, we adopted optical/electrical biased electroreflectance spectroscopy (ER) and current-voltage (J-V) measurements. The p-n junction’s electric fields were evaluated through an analysis of the Franz-Keldysh oscillations (FKOs) in the ER spectra. By comparing the electrical and the optical biased ER and optical biased J-V results, we calculated the carrier densities contributing to the photovoltage (σ pv ) and the photocurrent (σ J). We confirmed that the σpv could affect the field screening for the p-n junction’s electric field. With increasing number of incident photons (σ ph ), the ratio of σ pv to σ J was almost constant. From these results, for a concentrated photovoltaic device, we propose that the photovoltaic effect can affect the solar cell’s efficiency in the relatively high excitation intensity region.