Semiconductivity of organic substances. Part 10.—Electrical properties of galvinoxyl, α,α-diphenyl-β-picryl hydrazyl and related solid free radicals

Abstract

The semiconductivity and photoconductivity of the solid free radicals galvinoxyl (2,6-di-tert-butyl-α(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene) p-tolyloxy radical) and DPPH (α,α-diphenyl-β-picryl hydrazyl) and related compounds have been examined. Their behaviour is similar to that of diamagnetic poly-cyclic hydrocarbons. They show semi-conducting properties with energy gaps in the range 1.4–1.6 eV whether as single crystals, films or compressed powders. In sandwich cells the photocurrent follows the absorption spectrum, except for the lowest energy band where no significant photocurrent is observed.