Electrogenerated Chemiluminescence 34 . Photo - Induced Electrogenerated Chemiluminescence and Up - Conversion at Semiconductor Electrodes

Photosensitized oxidations or reductions at pand n-type GaAs and InP semiconductor electrodes of aromatic species in aprotic solvents leading to electrogenerated chemiluminescence (ECL) are described. The energy of the irradiating light equal to the bandgap energy of the semiconductor and the electrical energy input couple to produce excited states which eventually produce emission at shorter wavelengths. Intense ECL is observed by alternately generating radical cations and radical anions at an illuminated semiconductor electrode with smaller potential excursions than required on metal (platinum) electrodes. Photoassisted electrode processes of a number of species (e.g., aromatic hydrocarbons and heterocyclic compounds) at semiconductor electrodes in aprotic solvents have been described (1-5). These studies have demonstrated that electrochemical oxidations at n-type semiconductors occur at less positive potentials (or reductions at p-type semiconductors at less negative potentials) than are required to carry out the same process at an inert metal (e.g., Pt) electrode. These processes thus involve the partial conversion of light energy to chemical energy in the electrogenerated species. When the electrogenerated species (e.g., radi* Electrochemical Society Student Member. * * Electrochemical Society Active Member.