Enhancing the efficiency and stability of inverted perovskite solar cells by using 6-(trifluoromethyl)nicotinic acid as a potent defect passivator

Abstract

The intrinsic defect density inherent in perovskite materials profoundly impacts the photovoltaic performance and long-term stability of perovskite solar cells (PSCs). Additive engineering emerges as a promising strategy to address these challenges by attenuating defects through modulation of crystal growth and morphology regulation of the perovskite film. In this context, 6-(trifluoromethyl)nicotinic acid (TFNA), a small heterocyclic molecule containing carboxylic acid (COOH) and trifluoromethyl (CF₃) groups, is utilized as a multifunctional additive. The functional groups of TFNA effectively anchor the perovskite framework, enabling controlled crystallization and enhancing the grain size of the perovskite film, thereby reducing trap density and improving charge transport. Consequently, TFNA suppresses non-radiative recombination and minimizes charge-transport losses. As a result, champion devices demonstrate significantly enhanced photovoltaic parameters, achieving a higher efficiency of 20.45% compared to pristine devices at 16.64%. Additionally, the hydrophobic nature of the CF₃ group provided protection against moisture penetration, allowing the optimized PSCs to retain 75% of their initial power conversion efficiency (PCE) under conditions of 45 ± 5% relative humidity and room temperature, compared to ∼40% for pristine devices.