Organic field effect transistors (OFETs) of poly(p-phenylenevinylene) fabricated by chemical vapor deposition (CVD) with improved hole mobility

This study demonstrates organic field effect transistors (OFETs) of chemical vapor deposited poly(p-phenylenevinylene) (PPV). The optical and electrical properties of the films are reported. It is found that the grain sizes of the film can be engineered by surface treatment of the oxide of the Si/SiO2 substrate in the transistor with a self assembled monolayer (SAM) of octadecyltrichlorosilane (OTS). The enhancement of domain sizes of the grains with surface treatment leads to an increase in hole mobility to 1.4 × 10−4 cm2/V s, which is 1000 times higher than that reported for solution processed PPV field effect transistors. A comparison of the hole mobility between CVD grown PPV films and those reported for PPV and its derivatives, grown by spin coating or drop casting, shows that CVD provides an optimized alternative for growth of devices. It is shown that a low annealing temperature of 180 °C is enough to achieve polymerization. Film deposition by CVD has the advantage that up-scaling, with a fine control on the film thickness, is possible without compromising on the electrical/morphological properties. A vacuum based method of polymer deposition opens up the prospect of hybrid devices based on small molecules and polymers.