Über die Photoleitung flüssiger Aromaten bei Anregung des Triplett-Zustandes

Abstract

Irradiation of the aromatic compounds Benzene, Naphthalene, Biphenyl, Pyrene, and Benzophenone in the liquid state with a Xenon-arc-lamp produces a photocurrent, if an external d. c. voltage is applied. This current is independent of the dark-conductivity and increases linearily with light-intensity. It does not appear, if blocking quartz electrodes are used. The spectral response curve shows one peak at the wavelength of the forbidden singlet-triplet absorption-band of the compound and another at the longwave-edge of the singlet-absorption-region. A model is proposed basing on the idea of triplet-exciton formation (T1) by direct S0—T1 transitions and by transitions from S1 to T1 states (intersystem-crossing). The triplet exciton can migrate to the electrodes and dissociate there for energetic reasons. The released electron is received by the electrode. The cation remains either in the liquid or recombines with the electron. The cation can contribute to the photocurrent only when the dissociation has happened at the anode. In agreement with the measurements, dissociation requires conducting electrodes and follows monomolecular kinetics.