Dipolar Chemical Bridge Induced CsPbI3 Perovskite Solar Cells with 21.86 % Efficiency

CsPbI3 perovskite receives tremendous attention for photovoltaic applications due to its ideal band gap and good thermal stability. However, CsPbI3 perovskite solar cells (PSCs) significantly suffer from photovoltage deficits because of serious interfacial energy losses within the PSCs, which to a large extent affects the photovoltaic performance of PSCs. Herein, a dipolar chemical bridge (DCB) is constructed between the perovskite and TiO2 layers to lower interfacial energy losses and thus improve the charge extraction of PSCs. The results reveal that the DCB could form a beneficial interfacial dipole between the perovskite and TiO2 layers, which could optimize the interfacial energetics of perovskite/TiO2 layers and thus improve the energy level alignment within the PSCs. Meanwhile, the constructed DCB could also simultaneously passivate the surface defects of perovskite and TiO2 layers, greatly lowering interfacial recombination. Consequently, the photovoltage deficit of CsPbI3 PSCs is largely reduced, leading to a record efficiency of 21.86 % being realized. Meanwhile, the operation stability of PSCs is also largely improved due to the high-quality perovskite films with released interfacial tensile strain being obtained after forming the DCB within the PSCs.