Solution processable lutetium phthalocyanine organic field-effect transistors

Abstract

Spun films of novel thermotropic liquid crystalline lutetium bisphthalocyanine sandwich complexes substituted with sixteen octyl chains are employed as active organic semiconducting layers in the fabrication of organic field-effect transistors (OFET). When the device is annealed under vacuum at 70 °C, an increase in the field effect mobility in the saturated regime by a factor of five is observed while the threshold voltage is reduced to half the value obtained for as-deposited films. The annealed devices exhibit an increase in on/off ratio by two orders of magnitude. An improvement in performance of OFETs annealed above the crystal to mesophase transition temperature is consistent with atomic force microscopic images indicating increases in grain sizes and decreases in mean surface roughness of the organic bisphthalocyanine films.