Interfacial Engineering of TiO2 by Graphene Nanoplatelets for High-Efficiency Hysteresis-free Perovskite Solar Cells

The role of graphene nanoplatelets (GnPs) in a CH3NH3PbI3-based perovskite device was investigated for the first time. The activated GnPs were introduced in the mesoporous TiO2 by a simple solution process. The morphology and optoelectronic properties of the anatase TiO2 layer was modified with the presence of GnPs. The introduction of GnPs modified the bad-gap properties and passivated the oxygen-based surficial defects, leading to reduced interfacial recombination and efficient charge-carrier transportation. An overall increment in the efficiency of 25% was observed from similar to 15 to 19% with the introduction of 2.0 wt % of GnPs. In addition, the device exhibits negligible hysteresis and enhanced stability. This work opens up new applications of GnPs to be utilized in solar cells and can be extended to other types of photovoltaic devices.