Highly Soluble and Oxidizing Organic Salts Doped Hole‐Transporting Layer Enables Efficient and Stable Perovskite Solar Cells

Abstract Chemical doping plays a crucial role in enhancing the charge transport and electrical conductivity of hole‐transporting layers (HTLs) in perovskite solar cells (PSCs), leading to improved device performance and stability. However, developing highly soluble and oxidizing chemical dopants that ensure stable PSCs remains a significant challenge. Herein, the design and synthesis of a novel organic radical cation salt, XD1 , comprising tris(4‐methoxyphenyl)aminium as the radical cation and bis(trifluoromethane)sulfonimide (TFSI⁻) as the anion, are reported. XD1 exhibits excellent solubility in various organic solvents and demonstrates strong oxidative capability, significantly boosting the conductivity of HTLs by three orders of magnitude. Compared to conventional dopants like LiTFSI and Magic Blue (MB), XD1 ‐doped Spiro‐OMeTAD films demonstrate superior characteristics, including enhanced compactness, uniformity, and hydrophobicity. Remarkably, PSCs incorporating 2.0 mol% XD1 achieve a maximum power conversion efficiency (PCE) of 25.25%, surpassing the 24.44% PCE of LiTFSI‐doped cells. Particularly, unencapsulated PSCs with XD1 retain over 91% of their initial efficiency after 1 000 h of continuous one‐sun illumination at 85 °C in an N₂ atmosphere. This work represents a significant advancement in the development of highly soluble and efficient dopants for efficient and stable PSCs.