Temperature dependence of fluorescence and phosphorescence of the triphenylamine dimer 3-methyl-TPD

The triphenylamine dimer, N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD) as neat film, and as guest in polystyrene (PS), 4,4′-N,N′-dicarbazole-biphenyl (CBP), and polycarbonate (PC) films is investigated by luminescence spectroscopy. The luminescence quantum distributions, EL(λ), are determined over a wide temperature range from 10 K to 291 K by photo-excitation in the singlet absorption region of TPD. The singlet-excited phosphorescence quantum distributions are extracted by fluorescence contribution subtraction. The absolute intrinsic luminescence quantum yields, fluorescence quantum yields, and singlet-excited phosphorescence quantum yields are calculated from the quantum distributions. Even at room temperature phosphorescence emission is obtained. The triplet-singlet radiative lifetimes are determined from extracted S0–T1 absorption and emission spectra, and the phosphorescence lifetimes are estimated from the phosphorescence quantum yields and the radiative phosphorescence lifetimes. In TPD neat films fluorescence reduction by self-quenching is observed. CBP host to TPD guest excitation transfer is observed in the case of excitation into the CBP absorption region.