Bifacial perovskite/silicon tandem solar cells

Perovskite/silicon tandem solar cells are a rapidly emerging class of high-efficiency photovoltaic (PV) devices that have demonstrated excellent power conversion efficiencies (PCEs) while promising low-cost manufacturing. In recent years, this technology has been pushed increasingly closer to market entrance. Yet, for true commercial success, PCEs also need to be stable, in line with the warranty certificates of commercial crystalline-silicon (c-Si) PV modules. Bifacial tandem solar cells that collect light at both their sunward and rear side by exploiting the albedo—the scattered and reflected photons from the ground—offer a promising pathway toward a greater stability and energy yield. Thanks to the additional photons arising from the albedo, bifacial solar cells may generate a current larger than their conventional monofacial counterparts, enabling a higher performance. For bifacial monolithic tandems, exploiting such current enhancement requires current matching between top and bottom cells, which mandates the use of a bromide-lean, narrow-band-gap perovskite that is known to suppress halide segregation, thereby significantly improving device stability. In this perspective, we discuss bifacial perovskite/silicon tandem technology in depth, highlighting its great appeal, thanks to its combination of enhanced performance and improved stability with promising low costs, thereby representing a key future technology at the utility scale that can contribute to the formation of a carbon-neutral sustainable economy.