Dopant‐Free Hole‐Transporting Material with Enhanced Intermolecular Interaction for Efficient and Stable n‐i‐p Perovskite Solar Cells

Developing low-cost, efficient, and stable dopant-free hole-transporting materials (HTMs) in perovskite solar cells (PVSCs) is essential to their commercial deployment. Herein, the synthesis of a novel spirofluorene-dithiolane based small molecular HTM, SFDT-TDM, through facile and low-cost synthetic routes is reported. The C^-H^…π interactions in adjacent SFDT-TDM are beneficial for high hole mobility and the methylthio groups in SFDT-TDM can serve as Lewis bases to passivate the defects on the surface of perovskite films, leading to suppressed non-radiative recombination and enhanced charge extraction at the perovskite/HTM interface. As a result, Cs_xFA_1−xPbI₃ based PVSCs with SFDT-TDM as the HTM realize champion power conversion efficiencies (PCEs) of 21.7% and 20.3% for small-area (0.04 cm²) and large-area (1.0 cm²) devices with negligible photocurrent hysteresis, respectively. Additionally, all-inorganic CsPbI_3−xBrx based PVSCs with SFDT-TDM demonstrate an impressive PCE of 17.1% along with excellent stability. This work highlights the great potential of the spirofluorene core for exploring low-cost and dopant-free HTMs for PVSCs with high efficiency and stability.