The spectral assessment of the origin of the polaronic contribution to charge transport in a highly conjugated triarylamine donor molecule Original Research Article

Site-selective fluorescence spectra have been measured to investigate the origin of the polaronic contribution to charge transport in 4-[bis(4-ethylphenyl)amino]phenyl-N,N,N′,N′-tetrakis(4-ethylphenyl)-[1,1′:3′1″-terphenyl]-4,4″-diamine doped poly(styrene). The spectra feature an unusually large Stokes shift of σ = 750 cm−1 and remain broad over the entire range of excitation energies. This is a clear indication of a torsional mode of relaxation that can account for the polaronic contribution observed in charge transport experiments.