Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells

Fully textured perovskite silicon tandem solar cells are promising for future low-cost photovoltaic deployment. However, the fill factor and open-circuit voltage of these devices are currently limited by the high density of defects at grain boundaries and at interfaces with charge transport layers. To address this, we devise a strategy to simultaneously enhance perovskite crystallization and passivate the perovskite/C60 interface. By incorporating urea (CO(NH2)2) as an additive in the solution step of the hybrid evaporation/spin-coating perovskite deposition method, the crystallization kinetics are accelerated, leading to the formation of the desired photoactive phase at room temperature. With that, perovskite films with large grain sizes (>1 μm) and improved optoelectronic quality are formed at low annealing temperatures (100°C). Concurrently, remnant urea molecules are expelled at the perovskite surface, which locally displaces the C60 layer, thus reducing interfacial non-radiative recombination losses. With this strategy, the resulting tandem solar cells achieve 30.0% power conversion efficiency.