High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer

Fabrication of organohalide perovskite materials on the top of ZnO nano-particles (NPs) has some beneficial advantages such as room temperature processing; however, the perovskite is not stable on ZnO NPs layer during the annealing process. In fact, there are only a few reports about the fabrication of perovskite solar cells on ZnO NPs layer. Herein, the decomposition mechanism of CH3NH3PbI3 perovskite materials on ZnO is reported, and it is found that the perovskite film on the top of the ZnO layer is converted into PbI2 during the annealing process due to the existence of hydroxide groups on the surface of the ZnO NPs. Depending on the annealing temperature, the reaction rate and the quality of the perovskite film can be changed. In order to tackle this problem, a quasi core shell structure of ZnO/reduced graphene oxide (rGO) quantum dots is synthesized and is employed as an electron transfer layer. In this regard, rGO not only passivates the surface of the ZnO NPs to prevent the reaction, but also extracts the charge carriers quickly from the perovskite layer to reduce the carrier recombination. Our results show that perovskite solar cell on ZnO/rGO layer exhibits a stable power conversion efficiency as high as 15.2% and 11.2% on fluorine-doped tin oxide (FTO) glass and polyethylene terephthalate (PET) substrates, respectively, under AM1.5G illumination.