Pulsed photoconductivity action spectra of β-metalfree phthalocyanine thin films

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Abstract
Using pulsed photoconductivity techniques, transient action spectra have been recorded on vacuum sublimed β‐metalfree phthalocyanine thin films in the wavelength range 360♯740 nm. Quantum efficiencies for carrier generation and carrier ranges were deduced assuming (a) range limited transport and (b) wavelength and field independent quantum efficiency.Carrier generation is shown to be a bulk phenomenon and the lowest excited singlet state is the common intermediate in the carrier generation process. Two sets of measurements have been performed, 5 and 12 weeks after sample preparation. The quantum efficiency changed from 2.5×10−4 to 10−3, probably due to an increase in the amount of absorbed oxygen.