Graphene/Strontium Titanate: Approaching Single Crystal–Like Charge Transport in Polycrystalline Oxide Perovskite Nanocomposites through Grain Boundary Engineering

Abstract

Grain boundaries critically limit the electronic performance of oxide perovskites. These interfaces lower the carrier mobilities of polycrystalline materials by several orders of magnitude compared to single crystals. Despite extensive effort, improving the mobility of polycrystalline materials (to meet the performance of single crystals) is still a severe challenge. In this work, the grain boundary effect is eliminated in the perovskite strontium titanate by incorporating graphene into the polycrystalline microstructure. An effective mass model provides strong evidence that polycrystalline graphene/strontium titanate nanocomposites approach single crystal-like charge transport. This phenomenological model reduces the complexity of analyzing charge transport properties so that a quantitative comparison can be made between the nanocomposites and strontium titanate single crystals. In other related works, graphene composites also optimize the thermal transport properties of thermoelectric materials. Therefore, decorating grain boundaries with graphene appears to be a robust strategy to achieve "phonon glass–electron crystal" behavior in oxide perovskites. ; This work has received the funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie individual Fellowship programme No 800031. The authors gratefully acknowledge the support provided by the EPSRC (awards: EP/I036230/1, EP/L014068/1, EP/L017695/1). The authors would also like to acknowledge funding from the National Science Foundation (DMREF-1729487 and DMREF-1333335). As the Research Chair in Carbon Materials, IAK gratefully acknowledges support from Morgan Advanced Materials/ Royal Academy of Engineering. All research data supporting this publication are directly available within the publication.