Charge trapping for controllable persistent luminescence in organics

Persistent luminescence, long-lived emission from inorganic or organic materials after the cessation of excitation, receives considerable attention in the field of optoelectronics. Despite great achievements in the past decades, the performance of organic materials still lags behind their inorganic counterparts, which have thousands of years of history. This is largely caused by the limited understanding of the mechanisms involved in organic materials. Here we report trap-induced persistent luminescence (TIP) in organic host-guest materials, with controllable trap depths from 0.11 to 0.56 eV and tunable afterglow emission at wavelengths from 507 to 669 nm via energy level engineering. The TIP phenomenon in a typical TN@TPBi film lasts for more than 24 h, with additional energy stored at room temperature for over 1 week. It is found that the trap depth in TIP is probably determined by the energy gap between the lowest unoccupied molecular orbitals of the radical anions of the host and gu..., Materials and characterizations: TN was synthesized in two steps including dehydration reaction and palladium catalyzed Suzuki cross-coupling reaction, followed by comprehensive characterizations of nuclear magnetic resonance (NMR) spectroscopy (Advance III 500 MHz NMR, Bruker), mass spectrometry (FTICR MS, Bruker), and element analysis (Vario EL III, Elementar).
TN@TPBi film fabrication. A mixture of TN and TPBi (total 1 mmol, around 60 mg) was heated up to 350 °C on a quartz substrate in a glovebox. After melting, the molten liquid of materials was stirred thoroughly, then cooled rapidly to RT and encapsulated under a nitrogen atmosphere using ultraviolet-cured epoxy resin and glass covers. The other blend films were fabricated with the same method.
Photocurrent device fabrication: Si-SiO2 substrate was washed with deionized water, acetone, and isopropanol sequentially, and dried in drying oven at 100 °C. The gold as parallel electrodes were evaporated on the substrate at 3.5 Å/s when..., , # Charge trapping for controllable persistent luminescence in organics

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**Figure 2 |  Photophysical properties of the 1 wt% TN@TPBi phosphor. b**, Steady-state photoluminescence (PL), phosphorescence (delay time: 25 ms), and TIP spectra (delay time: 1 h and 9 h) at RT. **c**, TIP decay curve of the TN@TPBi phosphor after excitation by a 365 nm UV lamp for 300 s at RT. The noise signal is given for comparison (grey dots). 0.32 mcd/m2 is the minimum standard value for inorganic TIP phosphors (100 times higher than the limit of the sensitivity of the human eye in a dark-adapted condition). **d**, TIP decay curves under different thermal simulation conditions. Notably, the excited TN@TPBi phosphor was kept at RT for 10 min, and then heated to 300 (blue), 350 (green), and 400 K (red) with a heating rate of 50 K/min. **e**, TIP decay curves with 980 nm NIR photo-stimulation in a continuous output mode...