Oxygen doping in nickel oxide for highly efficient planar perovskite solar cells

Currently the performance of inverted perovskite solar cells is still lower than that of normal structured devices, due to the imperfect band alignment between the perovskite and hole transport layer (NiO). Herein, we found that the presence of oxygen during film preparation could lower the Fermi level of NiO and decrease the energy mismatch between the perovskite and NiO. The decreased mismatch benefited the VOC of the devices as well as the charge transfer between NiO and the perovskite. In addition, the utilization of Cs-MA-FA mixed ion-based perovskites as absorbers could increase the light response range and improve the thermal and moisture stabilities of perovskite solar cells. Finally, we achieved a stable performance output of 19.2% for inverted planar perovskite solar cells without any hysteresis.