Harnessing CuO-Doped 4--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--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 CuO as a spiro-OMeTAD additive to reduce voids and improve the quality of films. Incorporating CuO 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 CuO-modified HTM reaches 14.17%, surpassing that of the control HTM at 12.25%. Furthermore, the introduction of CuO 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.