J-W Lamberink

A precise additive regulation strategy using phenylethylammonium chloride (PEACl) enables uniform distribution of SnF₂ at grain boundaries via hydrogen bonding and steric hindrance. This suppresses SnF₂ phase segregation, promotes homogeneous Sn–Pb perovskite crystallization, and effectively releases lattice strain, resulting in efficient and stable all-perovskite tandem solar cells.

Abstract

Tin fluoride (SnF₂) serves as an indispensable antioxidant in Sn–Pb perovskite solar cells, playing a critical role in the development of efficient all-perovskite tandem architectures. However, excessive SnF₂ often suffers from aggregation challenges, inevitably causing phase separation and tensile strain within the perovskite films, severely compromising device efficiency and stability. In this study, we report a precise regulation strategy by employing phenylethylammonium chloride (PEACl) to modulate the distribution of excess SnF₂. The hydrogen bonding between PEACl and SnF₂, coupled with steric hindrance effects, enables uniform dispersion of SnF₂ at grain boundaries, effectively suppressing SnF₂ phase segregation and promoting homogeneous crystallization of Sn–Pb perovskites. Moreover, it is revealed that the precise regulation of SnF₂ distribution through PEACl effectively releases local strain in perovskite thin films. Single-junction Sn–Pb devices treated with the SnF₂+PEACl demonstrate an exceptional power conversion efficiency (PCE) of 23.52%, substantially outperforming control devices at 20.83%. The optimized two-terminal (2-T) monolithic all-perovskite tandem solar cells achieve a remarkable PCE of 28.89%. Notably, these tandem devices maintain over 80% of their initial efficiency after continuous operation at maximum power point under one-sun illumination for 670 h, exhibiting excellent long-term stability.