Rear heterojunction GaInP solar cells for improved performance at elevated temperatures

We present the characteristics of n-on-p front-junction (FJ) and rear-heterojunction (RHJ) GaInP solar cells at operating temperatures (T) up to 400 degrees C. Photovoltaic cells with efficient operation at high T may be important for satellite missions near the sun or as laser power converters for sensors operating in harsh environments, such as gas turbines or hypersonic vehicles. In this work, we show that the time-resolved photoluminescence lifetime (tTRPL) in both lattice-matched (LM) n-Ga0.51In0.49P and metamorphic (MM) n-Ga0.37In0.63P double heterostructures (DHs) increases significantly with T. In contrast, the tTRPL values in their p-type counterparts are lower and decrease with T. We go on to demonstrate both LM and MM solar cells in FJ and RHJ configurations. For both LM and MM cells, the internal quantum efficiency (IQE) of the RHJ cells increases significantly up to T = 300 degrees C due to the increase in both tTRPL and the linear increase in diffusivity with T. In contrast, the IQE of MM FJ cells drops slightly with increasing T, while the IQE of LM cells drops sharply. RHJ cells maintain higher VOC and fill factor than their FJ counterparts, leading to a significant efficiency advantage at T = 200-400 degrees C. Taken together, our work shows that MM cells perform well at elevated temperatures and that RHJ cells are promising for high-T operation.