Simulating tandem solar cells

The optimal bandgaps of a stacked solar cell were usually derived under standard test conditions. We studied tandem solar cells consisting of two serially-connected thin-film solar cells under different weather and temperature, daily and seasonal conditions. Each cell was described with one-diode model. Simulation results indicate that the optimal bandgaps at higher temperatures differ from those derived under standard test conditions. The optimal bandgaps also change when the irradiation spectrum changes, e.g. on cloudy days. Despite of these differences we found out that on a yearly basis the seasonal changes have almost no influence on the optimal bandgaps.