Fig. 2: Host energy-level engineering to tailor trap depth in host-guest composites.

a PersL decay curves of the samples after UV irradiation (365 nm) for 3 min at RT. b TL glow curves of CPND@DPEPO with different heating rates of 2, 5, 10, 20, and 50 K min^–1. The sample was irradiated by UV light for 3 min at 100 K prior to the TL measurements. c, Estimation of trap depths with the Randall-Wilkins model. The trap depth (ε) was derived by plotting ln(T_m²/β) against 1/(k_B·T_m). d PersL spectra. The spectra were acquired during TL measurements at the peak temperature. e Absorption (Abs., dotted curves) and fluorescence spectra (Flu., solid curves). f Photographs of PersL in the dark (sample size: 2 × 2 × 0.1 cm³). The CPND@PPF, CPND@TSPO1, and CPND@DPEPO were irradiated with UV light at RT, kept for 10 min, and then heated to 350 K. The temperature curve is given on the top of the panel. Note that the color of the photographs with high PersL brightness may deviate from the original blue color due to overexposure of the camera sensor. Camera exposure settings: f/1.2, 5 s, ISO 80000. g Orbital configurations and energy levels of the radical anions CPND^•−, TMPyPB^•−, T2T^•−, PPF^•−, TSPO1^•−, and DPEPO^•−. The frontier molecular orbitals (FMO) energies were obtained from DFT calculations. The LUMO of the radical anions exhibited two sub-orbitals (α and β) due to two electron spin orientations in an open-shell system. h Comparison of the trap depths obtained from the TL measurements (top) and the energy gaps between \({{{{\rm{G}}}}}_{{{{\rm{L}}}}}^{{{{\rm{\bullet }}}}-}\) and \({{{{\rm{H}}}}}_{{{{\rm{L}}}}}^{{{{\rm{\bullet }}}}-}\) derived from the DFT calculations (bottom).