Direct measurements of intersystem crossing rates and triplet decays of luminescent conjugated oligomers in solutions.
Photothermal calorimetry and fluorescence spectroscopy were used to determine the relaxations of the photoexcited singlet state of two PPV and polyfluorene oligomers, (E,E)-1,4-bis[(2-benzyloxy)styryl]benzene (PVDOP) and ter(9,9'-spirobifluorene) (TSBF). The decay rates of different S1 relaxation channels, which include intersystem crossing (ISC), radiative, and nonradiative decay can be determined by the combination of photoacoustic calorimetry (PAC) and the time-correlated single photon counting (TCSPC) technique. The triplet state energy level is determined by the phosphorescence (Ph) spectra recorded at 77 K. The ISC yields are approximately 3% and 6% for PVDOP and TSBF, respectively. The T1 to S0 transition decay rate is acquired by PAC and photothermal beam deflection (PBD) measurements. The triplet state decay rate is 17 and 21 ms(-1) at room temperature. The Ph intensity decay at 77 K shows that the triplet state lifetime increases by 4 orders of magnitude, as compared to room temperature.
Chen
Hsin-Liang
HL
Department of Physics, National Taiwan University, Taipei 106, Taiwan.
Huang
Yi-Fang
YF
Hsu
Chao-Ping
CP
Lim
Tsong-Shin
TS
Kuo
Li-Chung
LC
Leung
Man-kit
MK
Chao
Teng-Chih
TC
Wong
Ken-Tsung
KT
Chen
Show-An
SA
Fann
Wunshain
W