Organic–Inorganic Hybrid Interfacial Layer for High-Performance Planar Perovskite Solar Cells

4,7-Diphenyl-1,10-phenanthroline (Bphen) is an efficient electron transport and hole blocking material in organic photoelectric devices. Here, we report cesium carbonate (Cs₂CO₃) doped Bphen as cathode interfacial layer in CH₃NH₃PbI_3–xCl_x based planar perovskite solar cells (PSCs). Investigation finds that introducing Cs₂CO₃ suppresses the crystallization of Bphen and benefits a smooth interface contact between the perovskite and electrode, resulting in the decrease in carrier recombination and the perovskite degradation. In addition, the matching energy level of Bphen film in the PSCs effectively blocks the holes diffusion to cathode. The resultant power conversion efficiency (PCE) achieves as high as 17.03% in comparison with 12.67% of reference device without doping. Besides, experiments also demonstrate the stability of PSCs have large improvement because the suppressed crystallization of Bphen by doping Cs₂CO₃ as a superior barrier layer blocks the Ag atom and surrounding moisture access to the vulnerable perovskite layer.