Manipulating the Dimensionality and Ionic Conductivity of CH3NH3PbBr3 Thin Film by Graphene quantum dots*

Metal Halide perovskites have attracted immense attention owing to their diverse applications in the fields of photovoltaics, optoelectronics, and energy storage. Ion migration is one of the interesting and mysterious processes in these materials. The facile manipulating of ionic- and electronic conductivities is one of the key features to make these materials a versatile candidate for next-generation energy conversion and storage applications. The electronic charge transport in perovskite materials is coupled with ion migration. In this work, we have reported a very facile strategy to control the dimensionality and ionic conductivity of the perovskite materials by introducing Sulphur doped graphene quantum dots (SGQDs) in methylammonium lead tri-bromide. We have performed impedance spectroscopy on an ITO/TiO2/perovskite/electrolyte device structure to demonstrate that the ionic conductivity is strongly dependent on the applied bias in SGQDs doped perovskite materials. SGQDs doped perovskites with lower ion migration as well as weaker electron-ion coupling compared to pristine perovskites. The SGQD acts like a filter for the ionic current while electronic transport is unaffected.