Performance of Monolithic Two‐ and Three‐Terminal Perovskite/Silicon Tandem Solar Cells Under Varying Illumination Conditions

Research on perovskite/silicon tandem solar cells is chiefly focused on devices in either two‐ or four‐terminal configurations (2T and 4T, respectively). Straying from these commonly investigated approaches, an alternative monolithically integrated device architecture using three terminals (3T) by combining a semi‐transparent perovskite top cell with a silicon heterojunction bottom cell featuring interdigitated rear contacts is presented. In the presence of a p/n recombination junction between subcells, a quasi‐2T configuration is obtained where the additional terminal functions as a current regulator. Thus, in contrast to 2T tandems, current matching between subcells is not necessary. Therefore, these devices are more stable against spectral variations, especially their voltages at maximum power point, as surplus current can be either injected into or extracted from the additional terminal. This is tested both by simulations and for the first time experimentally. Interestingly, the highest power conversion efficiency is not achieved by current matching but by maximizing current generation in the top cell. An experimental realization of a 3T tandem with p/n recombination junction and a power conversion efficiency of 24.9% is presented, thus confirming the general viability of the concept.