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

Abstract

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. © 2008 Elsevier B.V. All rights reserved.