Brightening Nonconventional Luminophores by Reconfiguring Hydrogen‐Bond Networks via Pressure Treatment

ABSTRACT Nonaromatic organic small‐molecule luminescent materials have garnered significant attention in optoelectronic devices and biomedical applications due to their simple structures and excellent biocompatibility. However, steric hindrance and a large bandgap often constrain their efficient luminescence. Herein, we employ pressure treatment to induce highly efficient room‐temperature phosphorescence, achieving a significant emission enhancement in weakly emitting nonaromatic barbituric acid crystals. The absolute photoluminescence quantum yield of the treated samples increases from an initial 2.22% to 12.53% through 20.0 GPa pressure treatment by the Walker‐type large‐volume press. Additionally, after different pressure treatments, the emission changes from blue light with CIE coordinates (0.17, 0.10) to blue‐white light with CIE coordinates (0.23, 0.34). Detailed experimental and theoretical analyses reveal that pressure treatment selectively reconfigures the hydrogen‐bond network, generating free hydroxyl groups. The engineered electronic structure introduces new n‐π * transitions, which allow an intersystem crossing pathway from the 1 (n, π * ) state to the 3 (π, π * ) state, enabling efficient occupation of triplet excitons. This work provides novel insights and approaches for regulating exciton behavior through hydrogen bond engineering in nonaromatic organic systems, thereby facilitating the development of efficient luminescent materials.