Effects of interfacial characteristics on photovoltaic performance in CH3NH3PbBr3-based bulk perovskite solar cells with core/shell nanoarray as electron transporter

CH3NH3PbBr3-based bulk perovskite solar cells with core/shell nanoarray as electron transporter are fabricated for the first time, and an efficiency of 4.31% under AM 1.5 illumination (100 mW/cm 2) was achieved. It is found that the open-circuit voltage in the CH3NH3PbBr3/nanoarray devices is determined by the difference between the conduction band of ZnO core and the highest occupied molecular orbital of CH3NH3PbBr3, but significantly correlates with the quasi-Fermi levels of the electrons in ZnO and the holes in CH3NH3PbBr3; thermal annealing is an effective way to enhance the device short-circuit current density by increasing charge generation and reducing interfacial charge recombination. In the CH3NH3PbBr3/nanoarray devices, interfacial characteristics are vitally important to the device performance, which is mainly embodied by the existing CdS shell that provides additional absorption contribution, passivates ZnO surface defects, reduces interfacial charge recombination, and eliminates the decomposition of CH3NH3PbBr3 on ZnO surface during the thermal annealing treatment for improving perovskite crystallinity to increase photocurrent. Our major findings are expected to provide a guide to design the effective interfaces for spatial separation of photogenerated charge carriers in efficient perovskite solar cells. (C) 2014 Elsevier Ltd. All rights reserved.