Exploration of novel organic luminophores that exhibit thermally activated delayed fluorescence(TADF) in the aggregated state is very crucial for advance of delayed luminescence-based applications such as time-gated b...Exploration of novel organic luminophores that exhibit thermally activated delayed fluorescence(TADF) in the aggregated state is very crucial for advance of delayed luminescence-based applications such as time-gated bio-sensing and temperature sensing.We report herein that synthesis, photophysical properties, molecular and crystal structures, and theoretical calculations of 2,6-bis(diarylamino)benzophenones. Absorption spectra in solution and calculations using density functional theory(DFT) method revealed that the optical excitation took place through intramolecular charge-transfer from one diarylamino moiety to an aroyl group. While the benzophenones did not luminesce in solution, the solids of the benzophenones emitted green light with moderate-to-good quantum yields. Thus, the benzophenones exhibit aggregation-induced emission. Based on the lifetime measurement, the green emission of the solids was found to include TADF. The emergence of the TADF is supported by the small energy gap between the excited singlet and triplet states, which was estimated by time-dependent DFT calculations. Thin films of poly(methyl methacrylate) doped by the benzophenones also showed green prompt and delayed fluorescence whose lifetimes were in the order of microseconds. Linear correlation between logarithm value of TADF lifetime and temperature was observed with the benzophenone in powder, suggesting that the benzophenones can serve as molecular thermometers workable under aqueous conditions.展开更多
Ultraviolet(UV)-emissive organic light-emitting diodes(OLEDs)have attracted growing attention as future UV-lighting sources following UV-LED.The design and development of highly efficient UV-emissive organic solids ar...Ultraviolet(UV)-emissive organic light-emitting diodes(OLEDs)have attracted growing attention as future UV-lighting sources following UV-LED.The design and development of highly efficient UV-emissive organic solids are essential for the advancement of UV-OLEDs.Reviewed herein are organic small molecules and polymers that exhibit UV emission in the aggregated state such as crystal,powder,and amorphous film.The UV-emissive molecules are in principle limited to those whose photoluminescence(PL)maxima are less than 400 nm and whose PL quantum yields in the aggregated state,which are useful for evaluating the potential of solid-state emitters,are reported.In cases that electroluminescence(EL)studies are demonstrated,the emission maxima and external quantum efficiencies with the device structures are also shown.Some exceptions are also included whose PL quantum yields are not reported,but UV-EL with an emission maximum of less than 400 nm is demonstrated.展开更多
基金supported by Grants-in-Aid for JSPS KAKENHI (15H03795)MEXT KAKENHI 15K13671+1 种基金the Nagase Science and Technology Foundationthe Ogasawara Foundation for the Promotion of Science and Engineering
文摘Exploration of novel organic luminophores that exhibit thermally activated delayed fluorescence(TADF) in the aggregated state is very crucial for advance of delayed luminescence-based applications such as time-gated bio-sensing and temperature sensing.We report herein that synthesis, photophysical properties, molecular and crystal structures, and theoretical calculations of 2,6-bis(diarylamino)benzophenones. Absorption spectra in solution and calculations using density functional theory(DFT) method revealed that the optical excitation took place through intramolecular charge-transfer from one diarylamino moiety to an aroyl group. While the benzophenones did not luminesce in solution, the solids of the benzophenones emitted green light with moderate-to-good quantum yields. Thus, the benzophenones exhibit aggregation-induced emission. Based on the lifetime measurement, the green emission of the solids was found to include TADF. The emergence of the TADF is supported by the small energy gap between the excited singlet and triplet states, which was estimated by time-dependent DFT calculations. Thin films of poly(methyl methacrylate) doped by the benzophenones also showed green prompt and delayed fluorescence whose lifetimes were in the order of microseconds. Linear correlation between logarithm value of TADF lifetime and temperature was observed with the benzophenone in powder, suggesting that the benzophenones can serve as molecular thermometers workable under aqueous conditions.
文摘Ultraviolet(UV)-emissive organic light-emitting diodes(OLEDs)have attracted growing attention as future UV-lighting sources following UV-LED.The design and development of highly efficient UV-emissive organic solids are essential for the advancement of UV-OLEDs.Reviewed herein are organic small molecules and polymers that exhibit UV emission in the aggregated state such as crystal,powder,and amorphous film.The UV-emissive molecules are in principle limited to those whose photoluminescence(PL)maxima are less than 400 nm and whose PL quantum yields in the aggregated state,which are useful for evaluating the potential of solid-state emitters,are reported.In cases that electroluminescence(EL)studies are demonstrated,the emission maxima and external quantum efficiencies with the device structures are also shown.Some exceptions are also included whose PL quantum yields are not reported,but UV-EL with an emission maximum of less than 400 nm is demonstrated.
