Harnessing Cu₂O-Doped 4-<i>tert</i>-Butylpyridine in Spiro-OMeTAD: Study on Improved Performance and Longevity of Perovskite Solar Cells

Recently, spiro-OMeTAD has gained prominence as a hole-transporting material (HTM) in high-performance perovskite solar cells (PSCs) due to its superior properties, cutting-edge HOMO state of energy, and solution processability. To promote hole mobility and conductivity, hygroscopic dopants and additives such as lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-<i>tert</i>-butylpyridine (TBP) are typically incorporated. However, these components can lead to aggregation and hydrolysis in ambient conditions, forming pinholes and voids in the films. In this study, we introduce Cu₂O as a spiro-OMeTAD additive to reduce voids and improve the quality of films. Incorporating Cu₂O alleviates TBP evaporation and provides a more consistent dispersion of Li-TFSI, decreasing the formation of pinholes and bubbles. As a result, additional anions are added to spiro-OMeTAD⁺ during the oxidation process, promoting the conductivity and hole mobility of the hole-transporting layer and thus boosting PSC performance. Thus, the power conversion efficiency (PCE) percentage of the Cu₂O-modified HTM reaches 14.17%, surpassing that of the control HTM at 12.25%. Furthermore, the introduction of Cu₂O protects the perovskite layer from water-induced deterioration, ensuring the stability of the PSCs. Our findings offer a promising approach to enhancing both the performance and stability of HTMs and PSCs.