Inductive effects in molecular contacts enable wide-bandgap perovskite cells for efficient perovskite/TOPCon tandems

Organic molecules that serve as hole-selective contacts, known as self-assembled monolayers (SAMs), play a pivotal role in ensuring high-performance perovskite photovoltaics. Optimal energy alignment between the SAM and the perovskite is essential for desired photovoltaic performance. However, many SAMs are studied in optimal-bandgap perovskites, with limited energy level modification specifically catering to wide-bandgap perovskites. Herein, we demonstrate that the energy level of SAMs can be systematically tuned in a stepwise manner via inductive effects in the conjugated moieties, enabling rational design tailored for specific perovskite bandgaps. The resulting WBG perovskite device based on our tuned SAM achieved a power conversion efficiency (PCE) of 22.8%. Integration with crystalline silicon TOPCon subcells further enabled the construction of a perovskite/TOPCon tandem device with a PCE of 31.1% (certified 30.9%).