Boosting Organic Long Persistent Luminescence by Enhancing Charge Separation Processes in Three-Component Systems

Organic long persistent luminescence (OLPL) materials feature power law emission decay and minutes-/hours-long afterglow durations because of retarded charge recombination. Unlike conventional room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) afterglow, the emergence of OLPL must include a charge separation process in its photophysical mechanism; consequently, the reported OLPL examples are much fewer than conventional afterglow materials. The incorporation of an electron donor or acceptor is conceived to interact with the long-lived excited state in conventional afterglow system, aiming to induce charge separation. Here, the study first builds two-component RTP/TADF afterglow systems composed of difluoroboron β-diketonate (BF₂bdk) dopants and organic crystalline matrices, and then introduces an electron-donating component into the two-component BF₂bdk-matrix systems to enable the charge separation processes. The resultant three-component materials exhibit visible-light-excitable OLPL afterglow lasting for several hours under ambient condition. Leveraging the efficient harvesting of singlet/triplet excitons by BF₂bdk and the protective environment provided by the crystalline matrix, the three-component materials exhibit an estimated OLPL efficiency of ≈10% and display OLPL brightness comparable to inorganic Sr₂Al₁₄O₂₅/Eu²⁺, Dy³⁺ materials. Furthermore, the obtained OLPL materials show promising applications in afterglow displays and information storage, marking a significant step toward practical implementations of organic afterglow materials.