Overcoming lattice mismatch for core-shell NaGdF@CsPbBr heterostructures.

The formation of core-shell heterostructures allows direct contact of two components for more efficient energy transfer while requires exquisite lattice match. Lattice mismatch is one of the most challenging obstacles for combining two components with different phases. In this work, we develop a strategy to overcome the limitation of lattice mismatch and grow α-phase lead halide perovskites (LHPs) onto β-phase lanthanide-doped nanoparticles (LnNPs) by seeding sub-8 nm LnNPs. This LnNP@LHP heterostructure effectively passivates the surface defects of LnNPs to obtain enhanced upconversion performance and enables two-way energy transfer within the heterostructures. We identify and prove that core size along with a high reaction temperature, instead of phase, is critical to overcome the lattice mismatch. Our strategy uncovers insights into the key factor of direct growth for heterostructures and we believe the current synthesis strategy for high-quality heterostructures will have strong application potential in optoelectronics, anticounterfeiting and light detection.