Harnessing Cu<sub>2</sub>O‑Doped 4-<i>tert</i>-Butylpyridine in Spiro-OMeTAD:\nStudy on Improved Performance\nand Longevity of Perovskite Solar Cells

Recently, spiro-OMeTAD has gained prominence as a hole-transporting\nmaterial (HTM) in high-performance perovskite solar cells (PSCs) due\nto its superior properties, cutting-edge HOMO state of energy, and\nsolution processability. To promote hole mobility and conductivity,\nhygroscopic dopants and additives such as lithium bis(trifluoromethanesulfonyl)imide\n(Li-TFSI) and 4-<i>tert</i>-butylpyridine (TBP) are typically\nincorporated. However, these components can lead to aggregation and\nhydrolysis in ambient conditions, forming pinholes and voids in the\nfilms. In this study, we introduce Cu<sub>2</sub>O as a spiro-OMeTAD\nadditive to reduce voids and improve the quality of films. Incorporating\nCu<sub>2</sub>O alleviates TBP evaporation and provides a more consistent\ndispersion of Li-TFSI, decreasing the formation of pinholes and bubbles.\nAs a result, additional anions are added to spiro-OMeTAD<sup>+</sup> during the oxidation process, promoting the conductivity and hole\nmobility of the hole-transporting layer and thus boosting PSC performance.\nThus, the power conversion efficiency (PCE) percentage of the Cu<sub>2</sub>O-modified HTM reaches 14.17%, surpassing that of the control\nHTM at 12.25%. Furthermore, the introduction of Cu<sub>2</sub>O protects\nthe perovskite layer from water-induced deterioration, ensuring the\nstability of the PSCs. Our findings offer a promising approach to\nenhancing both the performance and stability of HTMs and PSCs.