Unravelling the mechanism of interface passivation engineering for achieving high-efficient ZnO-based planar perovskite solar cells

摘要

Surface functional groups of ZnO electron transport layers are key factors to limit the power conversion efficiency of ZnO-based planar perovskite solar cells. We adopt ultraviolet ozone and annealing techniques to effectively remove parts of hydroxyl groups on the surface of ZnO layers, which improves the stability of perovskite layers in the crystallizing process, and reduces the number of pinholes and the crevices at the interface of ZnO/CH3NH3PbI3. Under the similar content of PbI2, the efficiency of the device based ZnO layers by ultraviolet ozone treatment for 20 min is not only three times of the device without treatment, but superior to that of the device based ZnO layers by annealing at 300 degrees C for 1 h. We find that the deep trap states and interstitial oxygen are the key factors to boost the photovoltaic performance of ZnO-based perovskite solar cells during the ultraviolet ozone treatment process, since they dominate the charge carries recombination lifetime at interface of ZnO/CH3NH3PbI3 and transport efficiency in the ZnO layers. When the treatment time of ultraviolet ozone reaches to 20 min, 17.65% efficiency of the device can be achieved, which is the champion efficiency of ZnO-based perovskite solar cells without any modified layers.