ELECTRIC-FIELD-INDUCED FLUORESCENCE QUENCHING AND TRANSIENT FLUORESCENCE STUDIES IN POLY(P-TERPHENYLENE VINYLENE) RELATED POLYMERS

Electric field induced fluorescence quenching has been investigated fo r a series of poly(p-terphenylene vinylene)s. The quenching efficienci es follow a strictly quadratic dependence on the applied field amplitu de with maximum values of about 10% at 200 V/mu m. Quenching occurs pr edominately at higher emission energies, resulting in a distinct blue- shift between the electro-modulated signal and the photoluminescence s pectra. These results provide evidence for the field assisted dissocia tion of neutral excitons within an inhomogeneously broadened density o f states (DOS). Experiments are also performed on devices prepared by the Langmuir-Blodgett-technique in order to evaluate contributions by the Stark effect. These experiments prove the electric field-assisted separation of charges onto separate chains. Transient photoluminescenc e experiments show fluorescence decay times ranging between 100 ps and 200 ps. The increase in relaxation times for larger detection wavelen gths gives evidence for spectral relaxation within the DOS. This leads to a consistent picture, where the balance between electric field ass isted dissociation of excitons competes with the radiative decay as we ll as the non-radiative decay processes. Implications on the spectral properties of electroluminescent devices are further discussed. (C) 19 98 Elsevier Science B.V.