Anomalies in Photovoltaic Characteristics of Multijunction Solar Cells at Ultrahigh Solar Light Concentrations

An anomaly appearing in the photovoltaic characteristics of triple-junction GaInP/GaAs/Ge and of the corresponding double-junction GaInP/GaAs solar cells at ultrahigh concentrations (more than 2000 suns) of incident light has been studied. The light current–voltage characteristics at various concentration ratios of incident light and the dependence of the open-circuit voltage on the photogenerated current were analyzed. It was shown that the anomaly is observed due to the tunnel diode connected back-to-back between the GaInP and GaAs subcells. This diode absorbs photons that pass across the GaInP layers and creates a counter photovoltage.