Electron charge transport in non-peripherally substituted copper phthalocyanine

Bottom-gate, bottom-contact organic thin film transistors (OTFTs) were fabricated using solvent soluble copper-1,4,8,11,15,18,22,25-octakis(hexyl)phthalocyanine as the active semiconductor layer. The compound was deposited as 70 nm thick spin-coated films onto gold source-drain electrodes supported on octadecyltrichlorosilane treated 250 nm thick SiO2 gate insulator. The analysis of experimental results showed the n-type field effect behaviour. Devices annealed at 100 oC under vacuum were found to exhibit the field-effect mobility of 0.0989 cm2 V-1 s-1, with an on/off current modulation ratio of ∼106, a reduced threshold voltage of 0.7 V and a sub-threshold swing of 2.12 V decade-1. The variations in surface morphology of the devices are found reflected considerably in the electrical measurements. The device contact resistance was found to be decreased as the gate bias increased and also with the annealing.