Efficient bifacial monolithic perovskite/silicon tandem solar cells via bandgap engineering

Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo—the diffuse reflected light from the environment—to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm–2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance. Bifacial solar cells can outperform monofacial cells by exploiting sunlight reflected off the ground surface. De Bastiani et al. show that bifacial perovskite/silicon tandem with an optimized bandgap can deliver a power density of 26 mW cm–2 and compare its performance to monofacial cells under outdoor conditions.