Impact of Current Collecting Grids on the Scalability of 3-Terminal Perovskite/Silicon Tandems with Bipolar Transistor Architecture

The heterojunction bipolar transistor (HBT) structure is an attractive solution for developing three-terminal perovskite/silicon tandem solar cells compatible with dominant silicon photovoltaic devices, such as PERC and heterojunction. However, in contrast to three-terminal tandems based on interdigitated back contact silicon cells, the three-terminal HBT requires the implementation of the third contact at the base (middle) layer. To this aim, the simplest solution is to access the base layer from the cell front side by implementing a grid layout with top interdigitated contacts (TIC). In this work, we elaborate on the feasibility of the HBT structure for 3T perovskite/silicon tandem solar cells. We report, based on optical and drift-diffusion simulations, proof-of-concept designs with high efficiency potential, and we analyze, with the aid of circuit level simulations, the implications of a TIC grid layout in the perspective of scaling up to large areas. Our results show that the HBT architecture is a promising candidate for developing 3T perovskite/silicon tandem solar cells compatible with industry standard silicon photovoltaics.