Researchers from Peking University, Eindhoven University of Technology, Chinese Academy of Sciences, Beijing Institute of Technology and University of Science and Technology of China have reported an effective strategy to resolve a long-standing trade-off in blue perovskite light-emitting diodes (PeLEDs), enabling high-efficiency devices through polymerization-driven nanocrystal confinement.
Metal halide perovskites are highly attractive for LED applications due to their excellent luminescence properties, but device performance has been constrained by a fundamental contradiction during in situ nanocrystal formation: achieving both high crystallinity and small crystal size. Small nanocrystals are essential for efficient radiative recombination, yet they are typically prone to structural disorder and defect formation, while larger crystals exhibit improved crystallinity but reduced emission efficiency. To address this, the researchers developed an in situ polymerization approach in which polymerizable ligands coordinate with perovskite precursor species during film formation. These ligands subsequently form a polymer network that imposes nanoscale spatial confinement on the growing nanocrystals. This confinement limits crystal growth while maintaining sufficient structural flexibility for lattice reorganization.
As a result, the perovskite films consist of nanocrystals that are both small and highly crystalline, achieving a photoluminescence quantum yield (PLQY) of 83%. The polymerizable monomers, designed with multiple coordination sites, enable extended interaction with perovskite clusters, facilitating controlled lattice rearrangement and reducing defect density.
The underlying mechanism was further clarified using combined experimental characterization and theoretical modeling. Density functional theory calculations revealed that multi-site O-Pb coordination between OEGA ligands and PbBr₂ precursors stabilizes intermediate structures and competes effectively with solvent coordination. Molecular dynamics simulations showed that ligand chain length plays a critical role, with medium-length OEGA providing an optimal balance between coordination strength, flexibility, and polymer network formation.
Together, these effects slow down uncontrolled aggregation of perovskite clusters while enabling gradual crystallization within a confined environment. This dynamic balance allows nanocrystals to reach an ordered cubic phase with reduced lattice distortion, thereby minimizing non-radiative recombination losses.
When integrated into devices, the resulting blue PeLEDs achieved an external quantum efficiency (EQE) of 21.8% at an emission wavelength of 491 nm, placing them among the highest-performing blue perovskite LEDs reported to date. The devices also exhibit improved spectral and operational stability compared to reference systems.
This work demonstrates how simultaneous control over ligand coordination chemistry, polymerization dynamics, and crystallization kinetics can overcome intrinsic material limitations in perovskite systems, providing a pathway toward high-performance blue emitters and advancing the broader development of perovskite-based optoelectronic technologies.
