Concentrating on critical bottlenecks in 1.68 eV wide-bandgap (WBG) perovskite solar cells (PSCs), specifically open-circuit voltage (VOC) losses and phase segregation caused by high defect density and low halide migration activation energy, a team of Zhejiang Normal University researchers has reported a synergistic modification strategy using aromatic ammonium salt isomers p-F-PEABr (linear ethylamine) and s-p-F-MBABr (branched α-methylbenzylamine), which share the molecular formula C₈H₁₁FBrN but differ in molecular configuration.
Utilizing a thermally stable MA-free FA₀.₈Cs₀.₂Pb(I₀.₈Br₀.₂)₃ as absorber, the team demonstrated that the mixture of s-p-F-MBABr and p-F-PEABr achieves optimal photovoltaic performance enhancement in WBG PSCs.
The researchers explained that s-p-F-MBABr enhances fill factor (FF) by forming a minimal two-dimensional (2D) perovskite phase and sterically passivating grain boundaries, while p-F-PEABr boosts VOC through 2D perovskite growth and defect suppression.
This synergy achieves champion PCEs of 22.11% with FF of 82% for opaque devices and 20.76% PCE with FF of 84% for semi-transparent PSCs.
The semi-transparent PSCs represent one of the highest reported FFs. Moreover, the mixture-modified opaque PSC retains more than 90% initial efficiency after 4272 h, and integration semi-transparent PSCs into four-terminal TSCs with Si PERC cells exceeds 28% efficiency, establishing this approach for high-performance photovoltaics.
