Realize larger grain size of CH₃NH₃PbI₃ film with reduced non-radiative recombination for high performance perovskite solar cells via precursor colloidal size engineering

In CH₃NH₃PbI₃ perovskite solar cells, enhancement grain size of CH₃NH₃PbI₃ to reduce the non-radiative at grain boundaries is an important way to reach high performance perovskite solar cell. However, it is still a challenge to enhance the grain size of CH₃NH₃PbI₃ through a simple and low cost way. In this work, a larger precursor colloidal size is realized through tuning morphology of precursor CH₃NH₃I using a polar solvent of ethanol during purification, yielding a larger grain size of CH₃NH₃PbI₃ film, and the as-prepared perovskite solar cells are shown to be dramatically increased to 17.49% with an increase in short circuit density, fill factor and open circuit voltage, as compared to that (14.28%) in the control device with CH₃NH₃I purified by non-polar solvent of diethyl ether. The investigation result showed the increased efficiency of perovskite solar cells prepared by ethanol purification is ascribed to a faster charge transfer at CH₃NH₃PbI₃/TiO₂ interface resulting from the reduced grain boundary defects. Our work provides a route for improving the CH₃NH₃PbI₃ device efficiency through a simple yet effective approach.