Lithium‐Based Deep Eutectic in Spiro‐OMeTAD Enable Efficient and Stable Perovskite Solar Cells

and enhance the hole mobility of Spiro-OMeTAD, thereby promoting hole extraction and reducing non-radiative recombination losses. The device doped with DpyDS achieves an unprecedented power conversion efficiency (PCE) of 26.53% (certified 26.37%). After 1800 h of maximum power point tracking, the unencapsulated device retains 90.5% of its initial PCE under the ISOS-L-1I protocol. This work validates a promising deep eutectic strategy with LiTFSI in Spiro-OMeTAD, enhancing the PCE and long-term stability of PSCs.