Steric-Complementary Synergistic Strategy for High-Efficiency Monolithic Perovskite/Silicon Tandem Solar Cells

Abstract

Achieving efficiencies beyond 40% with perovskite/silicon tandems hinges on conquering the challenge of interfacial recombination without inducing deleterious trade-offs in charge extraction or stability. Herein, a steric-complementary synergistic strategy (SCSS) is introduced that resolves this dilemma using a molecular dyad of piperazine (Pip+) and phenethyl ammonium (PEA+) cations. It is demonstrated that the compact Pip+ cation infiltrates and neutralizes deep-level surface defects inaccessible to larger molecules, while its bulkier PEA+ counterpart co-assembles into a robust, hydrophobic canopy that shields the interface from environmental stressors. This cooperative architecture synergistically suppresses trap-state density and mitigates resistive losses, simultaneously enhancing charge extraction and device stability. Consequently, the tandem devices achieve a certified power conversion efficiency (PCE) of 32.12%. These tandems also exhibit exceptional operational stability, retaining over 80% of their initial efficiency after 1000 h of continuous one sun illumination under maximum power point tracking. This work establishes that engineering interfaces with sterically mismatched, functionally complementary molecules is a potent strategy, providing a clear pathway toward next-generation tandem photovoltaics that are both highly efficient and truly durable.