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

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 perovskite strontium titanate (STO) by incorporating graphene into the polycrystalline microstructure. An effective mass model provides strong evidence that polycrystalline graphene/strontium titanate (G/STO) 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 STO 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. In oxide perovskites, a major factor limiting electronic performance is the existence of grain boundaries. Carrier mobilities in polycrystalline oxide perovskites are orders of magnitude less than the carrier mobilities in single‐crystals with grain boundaries. By the incorporation of graphene into perovskite strontium titanate, the grain boundary effect is eliminated. Structurally polycrystalline graphene/strontium titanate nanocomposites approach single‐crystal charge transport behavior.