Self-constrained octahedral distortion for high-performance quasi-2D blue perovskite light-emitting diodes

The soft nature of perovskite lattices enables precise modulation of crystal structures through A-site cation doping to tailor electronic band structures and carrier dynamics. However, there remains a lack of lattice distortion control methods capable of stabilizing octahedral distortion levels without inducing excessive lattice deformation as doping concentrations increase. This study systematically investigates the effects of A-site cations with varying radii on lattice distortion when incorporated into quasi-2D blue perovskite lattices. It was found that smaller ethylamine (EA) cations lead to uncontrollable lattice strain, while larger triethylamine (TA) cations fail to effectively regulate lattice distortion. In contrast, diethylamine (DA) cations induce self-constrained lattice strain independent of cation concentration. This self-constrained lattice tuning approach optimizes optical performance by significantly enhancing radiative recombination efficiency. Consequently, blue perovskite light-emitting diodes (PeLEDs) were successfully fabricated, achieving a record external quantum efficiency (EQE) of 14.15%. The self-constrained strategy offers substantial design flexibility for developing high-performance quasi-2D blue PeLEDs.