Organic thin-film transistors incorporating a commercial pigment (Hostasol Red GG) as a low-cost semiconductor

Abstract

Inexpensive carbon-based semiconducting materials are of interest for the manufacturing of organic thin-film transistors (OTFTs) for use in radio-frequency tags, gas sensors, printed logic circuits and flexible screens. The molecular organization of these materials at the interface with the dielectric layer in an OTFT is critical to device performance. We incorporated an inexpensive commercial pigment, 14H-anthra[2,1,9-m,n,a]thioxanthen-14-one (Hostasol Red GG, Solvent Orange 63), which has not been characterized before as a semiconductor in OTFTs. We found that of the four surface treatments used to modify the silicon dioxide (SiO2) dielectric, octyltrichlorosilane (OTS) had the greatest positive effect on device operation. We also illustrate the importance of moisture in the surface chemistry and its direct implications to film formation and device performance. Furthermore, increasing substrate temperature during physical vapor deposition of Red GG generally decreased device performance, despite increasing molecular organization and apparent grain size as characterized with atomic force microscopy (AFM). Optimized OTFTs had a field-effect mobility of up to 5 × 10−5 cm2/V, an on/off current ratio the order of 103 and a threshold voltage around 10 V. These results demonstrate the important role of processing conditions for Red GG-based OTFTs and could be applied to optimizing devices made with synthetic derivatives of Red GG for improved performance in this family of relatively inexpensive and unexplored semiconducting compounds.