Regulating Circularly Polarized Luminescence in Zero-Dimensional Chiral Hybrid Metal Halides

Abstract

Polarization reflects the inherent properties of light. Circularly polarized light, in which the electric field rotates in a circle along the direction of propagation, contains rich optical information and exhibits angle-independent characteristics. This feature makes it widely applicable in asymmetric synthesis, 3D display, and light-emitting devices. Research on circularly polarized luminescence (CPL) has garnered significant attention in recent years. CPL-active materials range from small molecules to supermolecules and from chiral rare-earth complexes to nanosuperstructures. With advancements in developing new materials and technology in chiral science, this field has rapidly developed, and extensive efforts are focused on the development of CPL-active materials with both high photoluminescence quantum yield (PLQY) and large luminescence dissymmetry factor (g_lum). Among these materials, zero-dimensional (0D) chiral hybrid metal halides (CHMHs) characterized by isolated inorganic polyhedra, which combine the chirality of organic cations with excellent photophysical properties of inorganic polyhedra, have emerged as a promising class of CPL-active materials. Despite recent advancements in the design and preparation of CPL-active 0D CHMHs, several challenges remain. Considering the demands of real applications, high PLQY, large g_lum value, and a range of CPL colors are all required.

In this Account, we introduce our research on the design and applications of CPL-active 0D CHMHs. It is divided into three parts. First, we discuss the mechanism of CPL generation in 0D CHMHs, from which the chiral cations serve as chiral inducers and the inorganic units act as luminophores. We then expand the discussion to the delicate modulation of CPL in 0D CHMHs, highlighting the relationship between hydrogen bonds, inorganic octahedral distortion, and CPL performance. Additionally, multicolor CPL in bright yellow, green, and ultraviolet is achieved by incorporating different metal halides. In the third section, we introduce novel applications of ultraviolet CPL (UV-CPL) and CP-mechanoluminescence (CPML) in enantioselective polymerization and encryption, respectively. Lastly, we point out the challenges and future research directions in this field. We hope this Account provides novel insights into the key parameters determining CPL performance and inspires further synthesis of novel CHMHs with tailored CPL properties.