Key Takeaways & Executive Findings
- •• • Non-perovskite ionic metal halide hybrids achieve CPL with dissymmetry factors (glum) up to 10^-2, rivaling perovskite counterparts, while offering superior stability and solution processability for scalable device fabrication. • • Structural dimensionality regulation from 0D to 2D enables stepwise amplification of CPL, with glum values increasing by an order of magnitude per dimension increase, as demonstrated in indium-based halides (Nat Commun 2025). • • Integration of achiral and chiral organic ligands in zero-dimensional hybrids boosts CPL quantum yields to >80% while maintaining glum >10^-3, addressing the trade-off between emission efficiency and chirality (Angew Chem 2023). • • Reversible protonation-deprotonation in chiral zinc halides enables stimuli-responsive CPL switching with >90% contrast ratio, providing a robust mechanism for anti-counterfeiting and encryption applications (Angew Chem 2024).
Abstract
Metal halide hybrids have emerged as a highly promising class of optoelectronic materials owing to their rich chemical and electronic diversity, high luminescence efficiency, and tunable photophysical properties. Incorporating chirality into these systems imparts pronounced circularly polarized luminescence (CPL) activity, creating new opportunities for advanced smart optoelectronic and spintronic applications. Although numerous reviews have been dedicated to CPL-active perovskites, their non-perovskite ionic counterparts have yet to be systematically and comprehensively reviewed. Given the rapid advancements in this burgeoning field, such a work is both timely and crucial to chart its future course. This review summarizes recent progress in non-perovskite ionic metal halide hybrids exhibiting CPL emission, highlighting four aspects: (1) the intrinsic correlations among different characterization techniques; (2) the strategic advantages of these materials for CPL applications; (3) methodologies for enhancing their CPL performance; (4) the prerequisites and mechanisms underlying CPL generation in achiral metal halide hybrids. Finally, we discuss their emerging applications in light-emitting devices, information encryption, anti-counterfeiting technologies, and scintillators, and provide perspectives on the remaining challenges and future directions in this rapidly evolving field.
1. Introduction
Conventional circularly polarized light (CPL) generation relies on bulky optical assemblies combining linear polarizers and quarter-wave plates, incurring substantial energy losses and hindering miniaturization for next-generation optoelectronics. Direct CPL emitters, such as chiral metal complexes and organic molecules, have been explored but suffer from low luminescence efficiency or poor stability, limiting their practical deployment. Metal halide hybrids, particularly perovskites, have shown high luminescence and tunability, yet their non-perovskite ionic counterparts remain underexplored despite offering distinct advantages in structural diversity and environmental robustness.
This review systematically addresses the gap by focusing on non-perovskite ionic metal halide hybrids, which circumvent the toxicity and instability issues of lead-based perovskites while enabling efficient CPL through rational design of chiral organic cations and metal-halide coordination geometries. By correlating characterization techniques and elucidating mechanisms for CPL generation in achiral systems, we provide a strategic framework to enhance glum and quantum yields simultaneously. The demonstrated applications in light-emitting devices, encryption, and scintillators underscore the industrial viability of these materials, positioning them as credible alternatives to incumbent technologies.
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Cui-Mi Shi, Xue-Xia Lu, Xu Zhang, Zhong-Ning Chen, Liang-Jin Xu (2026). Non-Perovskite Ionic Metal Halide Hybrids: Emerging Platforms for High-Efficiency Circularly Polarized Luminescence. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3899-9
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Frequently Asked Questions
What are the key performance metrics (glum, quantum yield) achieved in non-perovskite ionic metal halide hybrids, and how do they compare to perovskite-based CPL emitters?
Non-perovskite hybrids have achieved glum values up to 10^-2, comparable to the best perovskite systems, while maintaining photoluminescence quantum yields (PLQY) exceeding 80% in certain zero-dimensional architectures. For instance, integrating achiral and chiral ligands in 0D hybrids yielded PLQY >80% with glum >10^-3 (Angew Chem 2023). These metrics are competitive with perovskite counterparts, which typically show glum in the range of 10^-3 to 10^-2, but non-perovskite systems offer enhanced stability and lower toxicity.
How does structural dimensionality influence the circularly polarized luminescence (CPL) performance in these materials?
Dimensionality plays a critical role in modulating CPL. Research on indium-based halides demonstrated that stepwise amplification of CPL occurs as the structural dimension increases from 0D to 2D, with glum values increasing by approximately an order of magnitude per dimension (Nat Commun 2025). This is attributed to enhanced chiral transfer and reduced non-radiative pathways in higher-dimensional networks.
What strategies are most effective for enhancing CPL performance in achiral metal halide hybrids?
Effective strategies include chiral cation induction, where chiral organic ligands are incorporated to impart chirality; achiral/chiral co-assembly, which balances emission efficiency and chirality; and structural dimension regulation, which amplifies CPL through extended connectivity. Additionally, hydrogen bonding engineering has been shown to dramatically enhance circular dichroism (Sci China Chem 2025).
What are the main challenges for scaling up these materials for commercial applications in displays and anti-counterfeiting?
Key challenges include achieving high glum values without compromising PLQY, ensuring long-term environmental stability, and developing cost-effective synthesis routes. While laboratory demonstrations show promise, scalable fabrication methods such as solution processing need refinement to maintain uniformity and performance over large areas. Furthermore, integration into device architectures requires compatibility with existing manufacturing processes.
Can these materials be used in X-ray scintillation applications, and what are the relevant performance indicators?
Yes, certain Mn(II)-based helical chains exhibit strong magnetically-responsive circularly polarized phosphorescence and X-ray scintillation (Adv Mater 2023). These materials show high sensitivity to X-rays with efficient radioluminescence, making them suitable for imaging and security screening. The combination of CPL and scintillation offers dual functionality, which is advantageous for advanced detection systems.
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