Radical p‐Doping Spiro‐OMeTAD for Efficient, Stable and Self‐Healing Flexible Perovskite Solar Cells

Abstract

Abstract Spiro‐OMeTAD is the primary hole transport material (HTM) for high‐efficiency and stable flexible perovskite solar cells (FPSCs). However, the slow oxidation rate and susceptibility to film cracking under stress in Spiro‐OMeTAD lead to reduced device stability and efficiency. In this paper, a multi‐functional novel self‐healing nitroxide radical monomer, 4‐[[5‐(1,2‐dithiolane‐3‐yl)‐1‐oxopentyl]amino]‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (DT‐TEMPO), has been introduced to address these challenges. DT‐TEMPO, on one side, enhances the hole mobility and conductivity by p‐doping Spiro‐OMeTAD, while boosting the charge transfer process from perovskite to Spiro‐OMeTAD with an optimized energy level alignment on the other side. Additionally, DT‐TEMPO endows a self‐healing capability to Spiro‐OMeTAD through the introduction of dynamic breaking and reconstructing disulfide bond. The optimized perovskite solar cells achieve impressive power conversion efficiencies, 25.69% on rigid substrates (certified 25.30%), 21.23% on rigid mini‐modules, and 24.19% on flexible substrates. Remarkably, the FPSCs with DT‐TEMPO retain over 90% of their initial efficiency even after 20 000 bending cycles ( r = 6 mm) and recover to ≈95% of their initial value through the self‐healing process.