Integrated passivation strategy using multifunctional additives for tin–lead mixed perovskite solar cells†

Tin–lead mixed perovskite (TLP) solar cells hold significant commercial potential due to their ideal bandgap, which closely aligns with the Shockley–Queisser (S–Q) limit. However, their photovoltaic performance and stability remain inferior to lead-based perovskite solar cells, primarily due to Sn²⁺ oxidation, film decomposition, and phase segregation resulting from uncontrollable crystallization in TLP films. Here, we introduce a multifunctional additive, p-guanidinobenzonitrile hydrochloride (CG), that employs an integrated passivation strategy to simultaneously suppress Sn oxidation and passivate defects of TLP films. By leveraging the multifunctionality of CG's cyano and guanidino groups, which form both hydrogen and coordination bonds, this strategy synergistically mitigates Sn oxidation, passivates defects, and optimizes charge extraction. As a result, a single-junction TLP solar cell incorporating CG achieved a power conversion efficiency (PCE) of 23.13%. Furthermore, under continuous illumination in encapsulated devices, the T80 stability extended to 420 hours. This work presents a promising approach to addressing the challenges associated with TLP films, paving the way for improved performance and commercial viability.