The results of studies of the dependence of the photoresponse of films prepared by pyrolysis of cellophane and polyacrylonitrile (Orlon) films on the dark current, wavelength, temperature, construction details of cell mounting, and intensity and frequency of illumination are reported. Films heat treated to 600°C have an energy gap between the full band and the conduction band of about 0.25 ev and a resistivity of approximately 104 ohm-cm. The infrared response decreases quite sharply at the limit of the electronic absorption band (λ~5 microns). However, a photoresponse is also found for longer wavelengths in regions of strong molecular vibrational absorptions. The time constant of the photoresponse of the films is found to be the same in both the regions of electronic absorption and of the vibrational absorption. A decrease in time constant with increase in heat dissipation is observed. It is concluded that the photoresponse of the films studied is of a thermistor-bolometric nature.
© 1956 Optical Society of AmericaFull Article | PDF Article
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