Dopant‐free Starlike Molecular Hole Conductor with Ordered Packing for Durable all‐Inorganic Perovskite Solar Cells

Abstract All‐inorganic n‐i‐p perovskite solar cells (PSCs) using doped Spiro‐OMeTAD as hole transport material (HTM) suffer from photothermal stability due to ionic diffusion and radical‐induced degradation by the dopants. In this article, dopant‐free starlike molecule (N2, N2‐bis(4‐(bis(4‐methoxyphenyl)amino)phenyl)‐N5,N5‐bis(4‐methoxyphenyl)pyridine‐2,5‐diamine (BD)) is synthesized to engineer the stacking properties and delivered higher hole mobility than doped Spiro‐OMeTAD (3.2 × 10 −4 versus 1.76 × 10 −4 cm 2 V −1 s −1 ) as dopant‐free HTM. Starlike BD HTM has a twisted acceptor unit and strong dipole, forming crystalline and ordered packing film to ensure intramolecular charge transfer and improve mobility. The BD CsPbI 3 PSCs deliver the maximum efficiency of 19.19%, which is the highest performance for all‐inorganic PSCs based on dopant‐free HTMs. Meanwhile, the ordered molecules‐packing blocks the migration channel of I − ions to metal electrodes and improves the device stability. BD‐based devices maintain more than 93% and 80% of the initial efficiency after 85 °C storage for 35 days and maximum power point (MPP) tracking at 85 °C for 1000 h, respectively.