Top-Interface Nonfullerene Modification of Tin-Based Perovskite Solar Cells: Discerning Multifaceted Functions of Y6 Acceptor

Tin halide perovskite solar cells (Sn-PSCs) suffered from efficiency and stability deficits due to intrinsically interfacial recombination and Sn2+-oxidation. This study introduces a benchmark nonfullerene acceptor Y6 at the top interface of p-i-n Sn-PSCs via antisolvent processing. Y6 acts to coordinate with Sn2+ ions via its C═O and C≡N groups, thus passivating defects and suppressing oxidation, while the hydrophobicity permits self-encapsulation and enhances the moisture resistance. Furthermore, n-type attributes of Y6 reduce hole concentration at the surfaces of intrinsic p-type Sn-perovskite, creating a staggered band alignment that facilitates electron extraction and minimizes interfacial recombination. Noticeably, we reveal that the antisolvent processed Y6 engages in the crystallization process of Sn-perovskite and eliminates the occurrence of photogenerated carrier recombination induced by light absorption of Y6. Such nonfullerene modification at top interfaces synergistically yielded an ∼20% enhancement of the power conversion efficiency up to a champion 15.24%. Unencapsulated devices retained >90% of their initial PCE after 1000 h in an argon atmosphere.