Reduced open-circuit voltage loss for highly efficient low-bandgap perovskite solar cells via suppression of silver diffusion

Ag diffused across the PCBM layer increased the trap density and down-shifted the energy level of the perovskite layer. Fortunately, PCBM/ZnO layer efficiently suppressed the Ag diffusion, resulting in a perovskite solar cell with PCE of 18.1%.