Optoacoustic determination of photocarrier generation efficiencies of dye films

An optoacoustic method is used for the first time to study photoconductive efficiencies of thin dye films coated on a substrate. A piezoelectric transducer is attached to the substrate, and the dye film is excited by a modulated cw laser beam, of intensity less than 0.1 mW/cm2. Strong signal enhancement occurs when the laser modulation frequency is equal to a fundamental mechanical resonance frequency of the sample-transducer assembly (about 40 kHz in our experiment). The quantum efficiency for photocarrier generation is derived by measuring the decrease in optoacoustic signal when an electric field is applied to the sample.