Abstract: Organic long-persistent luminescent materials exhibit unique photophysical properties by sustaining light emission after excitation removal, demonstrating broad application potential in optoelectronic devices, flexible displays, information encryption, and bioimaging. The long-afterglow performance critically depends on key parameters including triplet exciton lifetime and phosphorescence radiative rate. While conventional experimental approaches face challenges in precisely elucidating the structure-property relationships between microscopic molecular electronic structures and macroscopic luminescent behaviors, computational chemistry methods offer powerful tools to uncover the underlying mechanisms. This study investigates a representative phenothiazine-based organic small-molecule system with long-persistent luminescence. Using density functional theory (DFT), we optimized both ground-state and excited-state geometries and calculated spin-orbit coupling constants. Through time-dependent DFT (TD-DFT) calculations, we evaluated energy-level transition characteristics and radiative decay pathways, thereby revealing the intrinsic correlation between molecular triplet-state lifetimes and long-afterglow radiative rates. By translating cutting-edge research into pedagogical resources, this experiment significantly enhances students’ comprehension of excited-state dynamics and material property relationships, providing a valuable case study for computational chemistry courses that combines academic rigor with practical applications.

Key words: Computational chemistry, Organic long-persistent luminescence, Ultralong organic phosphorescence, Spin-orbit coupling, Triplet exciton, Phosphorescence radiative rate, Teaching-oriented research