Pressure-enhanced ultra-deep-blue emission in unconventional layered metal halide with hybrid cations

High-energy and narrowband free-exciton emissions make two-dimensional hybrid metal halide perovskites (2D HMHPs) promising candidates for blue-light phosphors. However, achieving ultra-deep-blue emission through precise structural design remains a significant challenge. Herein, a unique 2D HMHP, [(4AMTP)PbBr2]2PbBr4 (4AMTP = 4-aminomethyltetrahydropyran), is employed for high-pressure research. The hybrid cation plays a crucial role in enhancing structural rigidity, effectively suppressing carrier trapping, and resulting in slight emission shifts at high pressure. Meanwhile, intense ultra-deep-blue emission is observed at 1.4 GPa, satisfying the BT.2020 standard of CIEy = 0.046. The key structural factor responsible for the emission enhancement is a substantial reduction in interlayer distance coupled with a notable decrease in intralayer distortion. Additionally, limited exciton migration, weakened electron–phonon coupling, decreased exciton binding energy, and suppressed phonon-assisted nonradiative decay, collectively promote the release of excitons from trap states.