Radiation-induced photoluminescence quenching of phenylene vinylene oligomer thin films

We have studied the radiation-induced photoluminescence (PL) quenching and the associated electronic structure modification of a light-emitting conjugated oligomer, namely, 1,4-bis[4-(3,5-di-tert-butylstyryl) styryl]benzene (4PV), in the absence of oxygen. We found that a short period of exposure to the radiation sources used in UV or x-ray photoelectron spectroscopies (UPS or XPS) resulted in total PL quenching in 4PV. Although there was no detectable change in the XPS C 1s core-level spectra UPS valence spectra indicated the disappearance of the vinylene peak upon exposure to UV radiation. This suggests the destruction of the vinylene groups, and the possible creation of radical species, which may serve as PL quenching sites. We also found that the modification in the electronic structure by Ca deposition masks that by radiation, although both quenches the PL effectively.