Deleterious Effect of Light Trapping on the Temperatures of Solar Modules

Increased temperatures generally reduce the efficiencies and life spans of photovoltaic modules. Experimental measurements show that thin-film GaAs modules operate more than 10°C cooler than Si modules. This study identifies the main thermal advantage of the GaAs modules as their high sub-bandgap reflection of 77%, which dwarfs the 15-26% measured on various Si architectures. This paper proves that the sub-bandgap reflection in modules with textured Si cells is fundamentally limited compared to reflection for cells without light trapping, due to the amplification of parasitic absorption that occurs with light trapping. N ow, this finding is being tested on perovskite-silicon tandems. It is expected that light trapping will increase the tandems' temperatures by several degrees.