Core/Shell Halide Perovskite/Chalcogenide Epitaxial Nanocrystals: Myth, Challenges and Imminent Reality

Core/shell nanocrystals of lead halide perovskites and chalcogenides are among the most sought after for preserving intense emission and ensuring stability under harsh conditions. Various surface protection strategies, such as organic ligand passivation, silica encapsulation, and polymer coatings, have been extensively explored, but epitaxial inorganic covalent semiconductor shells remain largely underdeveloped. Such shells can enhance both phase and environmental stability while maintaining overall particle sizes small. In this Perspective, we discuss the challenges and potential pathways toward understanding the core/shell halide perovskite where wide-band gap inorganic semiconductors serve as protective shells around perovskite cores. Using CsPbBr3 as a model system and ZnS as a representative shell material, we examine the feasibility of their epitaxial integration and underlying formation chemistry. We first summarize existing reports of successes and limitations in achieving well-defined core/shell architectures. Then we outline possible synthetic strategies and key characterization approaches required to realize such nanocrystals.