Multifunctional CNT:TiO₂ additives in spiro‐OMeTAD layer for highly efficient and stable perovskite solar cells

Abstract Hole transport layer (HTL) is very important for the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). As current state‐of‐the‐art HTL, Li‐TFSI doped spiro‐OMeTAD often suffers low conductivity and the hydrolysis of the additive Li‐TFSI, which significantly hinders the further improvement of PCE of PSCs. Besides, conventional spiro‐OMeTAD has no functional of directly passivating the perovskite crystal defects. Herein, multifunctional TiO₂ nanoparticles (NPs)‐modified CNT (CNT:TiO₂) doped spiro‐OMeTAD (spiro‐OMeTAD+CNT:TiO₂) HTL is reported for the first time. The incorporated CNT:TiO₂ not only significantly increases the conductivity of spiro‐OMeTAD+CNT:TiO₂, but also effectively passivates the crystal defects of perovskite layer. The optimized PSCs with spiro‐OMeTAD+CNT:TiO₂ HTL achieved a peak PCE of 21.53%, much higher than that (17.90%) of the conventional spiro‐OMeTAD based PSCs and also show significantly improved stability.image