Metal halide perovskites have emerged as highly promising candidate materials for light-emitting applications due to their tunable bandgap and excellent color purity. Despite significant progress in the research of perovskite light-emitting diodes (LEDs), their operational stability remains a critical challenge for practical applications. The corner-sharing [PbX₆]⁴⁻ octahedra centered by Pb²⁺ cations constitute the fundamental structural framework of these materials and primarily determine their electronic configuration and optical properties. However, the inherent structural instability of these octahedra is a major obstacle to commercialization.
The incorporation of mixed halide (Br─Cl) in the perovskite composition enables effective bandgap engineering to tune blue emission, making mixed-halide systems strong candidates for blue perovskite LEDs. However, significant chlorine incorporation inevitably introduces octahedral distortion due to differences in Pb─X bond lengths, leading to deep-level defect states, exacerbating non-radiative recombination, and reducing photoluminescence quantum yield. Furthermore, the soft ionic nature of perovskite crystals promotes significant ion migration under electrical bias, particularly pronounced in mixed-halide systems, resulting in the formation of metal halide defects, irreversible [PbX₆]⁴⁻ octahedra collapse, and severe halide segregation. Considerable efforts have been made to mitigate the structural instability of the octahedra. Structural degradation of the perovskite framework is primarily attributed to halide vacancies, which has prompted the introduction of targeted organic molecules containing oxygen, sulfur, and nitrogen atoms into the perovskite matrix. These functional ligands coordinate with unsaturated Pb²⁺ ions through electron donation or lone pairs. Despite these advancements, the introduction of such molecular additives inevitably brings in exogenous organic species, which often have poor binding affinity with the perovskite lattice. Additionally, precisely controlling crystallization kinetics to synthesize mixed-halide perovskite systems with higher crystal integrity and compositional uniformity has been emphasized as an effective way to alleviate lattice strain.
Recently, pseudohalide engineering has emerged as an effective strategy to improve the stability and emission characteristics of metal halide perovskites. Among various approaches, thiocyanate anions have been widely used to enhance the structural robustness and suppress defect formation in white or broadband-emitting perovskite systems, typically achieved through strong coordination or partial incorporation into the perovskite lattice. While these methods effectively improve overall stability, their applicability to quasi-2D blue-emitting perovskites is less straightforward, as the latter requires strict phase control and minimal lattice distortion to maintain high color purity. In this context, alternative additive strategies that stabilize perovskites primarily through interface and surface-mediated interactions (rather than lattice substitution) are particularly important. Heteroepitaxial growth techniques have proven effective in preparing defect-suppressed, crystallographically aligned, and stress-released perovskite films while enhancing the structural stability of the octahedral lattice. However, these methods require stringent control parameters in terms of process reproducibility and preparation conditions. Therefore, developing a simple and effective strategy to stabilize the tilted octahedral clusters remains a critical unmet need in this field.
He Yiming, Lyuchao Zhuang from Zhejiang Normal University, and Wei Gao from Shanghai Institute of Technology proposed a new strategy employing alkali metal trifluoromethanesulfonates as multifunctional lattice stabilizers. The sulfonate group is believed to coordinate with exposed Pb²⁺ ions through O─Pb─O bonds, effectively suppressing surface defects and preventing structural collapse. Furthermore, the alkali metal ions are thought to enhance structural stability through ionic interactions, while the fluorine component is believed to improve photochemical and moisture stability. This synergistic stabilization mechanism significantly suppresses non-radiative recombination and enhances energy transfer efficiency, achieving a remarkable photoluminescence quantum yield of up to 65.32%. Additionally, the strong electronegativity of the trifluoromethyl group is believed to contribute to the formation of uniform and smooth films, thereby facilitating carrier injection. Consequently, the optimized blue perovskite light-emitting diode achieved a maximum external quantum efficiency of 15.60%. This work establishes a generalizable strategy for octahedral structure stabilization, which is expected to accelerate the commercialization of high-performance blue perovskite light-emitting diodes.
