Buried Guanidinium Passivator with Favorable Binding Energy for Perovskite Solar Cells

Rational design and modification of the buried interface toward high performance perovskite solar cells (PSCs) are highly desired and challenging. Here, we demonstrate a series of guanidinium passivators with multiamine substitutions to shed light on the effective passivation geometry at the SnO 2 /perovskite heterojunction interface. Comparative theoretical and experimental studies reveal that the binding geometry of the highly polarized imine moiety in guanidinium passivators dominates its energetically favorable passivation on the SnO 2 surface, which decreases the trap density to 1.11 × 10 16 cm –3 with reduced interior/interface nonradiative recombination in the unsymmetrical aminoguanidine hydrochloride (Agu) platform. Consequently, the PSCs with buried Agu passivator deliver a champion power conversion efficiency (PCE) of 24.4% with an advanced open-circuit voltage ( V OC ) of 1.197 V and prolonged lifetime over 90% of the initial PCE after 900 h in ambient conditions.