Abstract
The effect of Cs-incorporated NiO (x) on perovskite solar cells with an inverted structure was investigated, where NiO (x) and PCBM were used as selective contacts for holes and electrons, respectively. It was found that the generation of an Ni phase in an NiO (x) layer was significantly suppressed by employing cesium. Furthermore, Cs-incorporated NiO (x) enabled holes to be efficiently separated at the interface, showing the improved photoluminescent quenching and thus generating higher short-circuit current. The effect of Cs incorporation was also prominent in the inhibition of recombination. The recombination resistance of Cs-incorporated NiO (x) was noticeably increased by more than three-fold near the maximum power point, leading to a higher fill factor of 0.78 and consequently a higher power conversion efficiency of 17.2% for the device employing Cs-incorporated NiO (x) .