Relaxation dynamics of excitons in thin quaterthiophene films on differentsubstrates

We compare picosecond time-resolved photoluminescence spectra of thin polyc rystalline films of quaterthiophene (4T) vapour deposited on two different substrates: highly oriented pyrolytic graphite (HOPG) and glass. At zero ti me delay, both films show the same highly resolved vibrational fine structu re as isolated 4T molecules. The fine structure remains over time on HOPG, but vanishes within the first 100 ps on glass and is replaced by emission f rom two luminescent traps. The results explain the line broadening in time- integrated (cw) spectra and yield information on the luminescence quenching in polycrystalline organic films. (C) 1999 Elsevier Science B.V. All right s reserved.