Dehydration-Resistant Amino Acid Additives for Stable and Efficient Perovskite Precursor Solutions and Solar Cells

Abstract

Additive molecules have been shown to enhance perovskite solar cell (PeSC) performance, but the effects of dehydration reactions caused by additives are not well understood. We found that α-glutamic acid (α-Glu) additives generate water molecules through amide bond formation in precursor solutions and films. While α-Glu initially improves device efficiency by passivating defects, these dehydration reactions degrade the solutions and films over time. In contrast, β-glutamic acid (β-Glu), a structural isomer, is less prone to dehydration, maintaining defect passivation and improving stability. Using β-Glu, we achieved a PeSC power conversion efficiency of 25.60%. These devices showed excellent stability, retaining 91% and 84% of initial efficiency after 2,000 hours of thermal annealing and 1,200 hours of continuous 1-sun illumination, respectively. Additionally, PeSCs from precursor solutions aged for 35 days retained 98% of the efficiency of those from fresh solutions, demonstrating remarkable stability and reproducibility.