Abstract
Organic fleld-effect transistors based on vapor deposited films of 2,9-diethylpentacene (C2-PEN), 2,9-dibutylpentacene (C4-PEN) and 2,9-dioctyIpentacene (C88-PEN) were successfully fabricated. All the alkylpentacene based OFETs showed typical p-channel PET characteristics, and the best field-effect mobility of 4.8x10-2 cm2V-1s-1 with on/off current ratio of ∼104 was obtained for the C2-PEN based OFET. Interestingly, the flled-effect mobility decreased as alkyl-chain length becomes longer. According to the molecular orbital calculations, the 2,9-dialkylpentacenes form doubly bent molecular structures in which the al1-anti alkyl groups are not lie on the same plane as that of the pentacene core. The alkyl-chains may hinder the intermolecular interactions and overlap, meaning the poor intermo]ecular charge transfer.
