Highly efficient monolithic Perovskite/Silicon bifacial tandem solar cells

Perovskite solar cells have been the focus of photovoltaics research in this past decade. Owing to their many favorable properties - like low cost solution processability, tunable bandgap and high efficiency, they have seen much attention in various types of solar cell designs. A promising technology has coupled perovskite cells with another semiconductor material in monolithic tandem solar cells, reaching record efficiencies of 29.15%. However, these kinds of devices require current matching condition to maximize the output of solar cells, making their fabrication challenging. Here, we propose the innovative bifacial tandem configuration to overcome current matching limits between the two sub-cells, by collecting photons from the surrounding environment, i.e. albedo. The extra light shining on our silicon bottom cell boosts the photogenerated current above monolithic tandem values. We show that the current density gain is more pronounced in perovskite solar cells with a narrow bandgap, 1.59 eV, than those with a wider one 1.7 eV. In other words, current matched tandems show little to no increase in efficiency with the extra albedo, while mismatched cells exhibit the most power, reaching up to ~28% in the best scenario. To give more credit to our work, we report outdoor data gathered in various locations around the world, and we show how different albedos have distinct effects on bifacial tandems.