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Updated: Jun 26, 2025

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
Published on: December 27, 2018
Photophysical analysis of dual fluorescence and phosphorescence emissions observed for semi-aliphatic polyimides at
Mayuko Nara1, Eisuke Fujiwara1, Aurimas Vyšniauskas2
1Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1-E4-5, Meguro-ku, Tokyo 152-8552, Japan. ando.s.aa@m.titech.ac.jp.
Abstract:
The photoluminescence (PL) properties of four types of blue fluorescent semi-aliphatic polyimides (PIs) derived from aromatic dianhydrides (ODPA, BPDA, HQDEA, and BPADA) and an alicyclic diamine (DCHM) were investigated at temperatures ranging from room temperature (RT, 298 K) to 30 K to analyse the origins of their non-radiative relaxation (NR) processes. These PIs exhibited significant increases in fluorescence (FL) intensity and lifetimes when lowering the temperature, stabilising below 100 K. The PIs containing ether (-O-) linkages showed a shoulder peak at around 500 nm below 150 K, which is attributable to phosphorescence (PH). These results show that the NR deactivation at RT includes three processes: intersystem crossing (ISC) from the excited singlet (S1) to the triplet (T1) state, temperature-dependent NR from the S1 state, which becomes suppressed below around 100 K, and temperature-independent NR. Based on the analyses of the temperature dependences, polymer structures, and quantum chemical analysis of molecular orbitals, we contemplate that the temperature-dependent NR is attributable to the excitation quenching by defect states mediated by excitation migration, and the temperature-independent NR may be caused by the deactivation of the excited state induced by molecular vibrations.
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