Molecular Synergistic Effect for High Efficiency Monolithic Perovskite/Perovskite/Silicon Triple‐Junction Tandem Solar Cells

Abstract Perovskite/perovskite/silicon triple‐junction tandem solar cells (TSCs) hold promise for high power conversion efficiencies (PCE). However, the efficiency is still relatively low due to the non‐radiative recombination losses in wide‐bandgap top cells. These losses, attributed to the interface defect states and energy level mismatches, present considerable challenges to realizing high‐performance and stable TSCs. Here, the molecular synergistic effect (MSE) is exploited to passivate interface in 1.95 eV top cells. Piperazine‐1‐carboxamide hydrochloride (PCACl) is combined, which possesses strong dipole moments and passivating functional groups that can bind with two neighboring uncoordinated lead ions and form hydrogen bonds with halide atoms at perovskite surface, with 1,3‐propane‐diammonium iodide, which can reduce interface recombination through field‐effect passivation. The MSE enabled by PCACl and PDAI 2 facilitates excellent energy level alignment and reduces non‐radiative recombination losses and light‐induced phase segregation. Finally, the target perovskite/perovskite/silicon triple‐junction TSC obtains an open‐circuit voltage of 3.07 V and a champion PCE of 25.2% (for a 1.035 cm 2 aperture area).