Applicability of the Band Model to Metal-Free Phthalocyanine Single Crystals

Abstract

The applicability of the band model to explain conduction in metal-free phthalocyanine is suggested by the equality of the thermal acrivation energy for electrical conduction, the energy for first optical absorption, and the energy for the initiation of photoconductivity. Further support for the band model is furnished by the similarities between phthalocyanine and anthracene since evidence has been advanced for the band-model approach in anthracene. The existence of tightly bound excitons is shown to be an unimportant consideration in conduction processes where the band model is applicable and the same equality among the aforementioned experimental data is obtained. Still further evidence for the band approach comes from Hall measurements. If the Hall data are interrpeted assuming the band approach is feasible, the calculated free-carrier concentration agrees quite well with that found from bulk current measurements.