Using unsorted single-wall carbon nanotubes to enhance mobility of diketopyrrolopyrrole-quarterthiophene copolymer in thin-film transistors

Organic thin film transistors (OTFTs) were fabricated for the first time using a semiconductor copolymer of diketopyrrolopyrrole-quarterthiophene (DPP-QT) and unsorted single walled carbon nanotubes (SWCNTs). Three different SWCNTs having different tube diameters, length, and shape were used to investigate the effects of carbon nanotubes’ properties on dispersion of the SWCNTs in DPP-QT polymer, as well as the mobility and current on/off ratio of the OTFTs. The DPP-QT polymer was able to selectively disperse two types of SWCNTs. An optimal SWCNT loading was found to be 1.5–2.5wt% for these SWCNTs, before the on/off ratio fell below 105 due to increased metallic tube content of the film. At this optimal loading, the field effect mobility was improved by a factor of two, with the maximum mobility reaching 1.3cm2V−1s−1, when the SWCNTs with a short length and small tube diameter were used.