The Effect Of Polystyrene Brush Modification Layer On Inkjet Printed OTFTs

Among the established printing technologies, inkjet printing is very promising because the film of the printed material can be directly patterned without the use of a mask or additional etching processes, and it has the advantage of high material utilization. For the OTFTs with inkjet-printed semiconductor layer, the interface modification is one of the most important methods to improve the crystallization of semiconductor film and produce desired device performance.In this thesis, PS brushes with different thickness were grafted on silica substrates by surface-initiated atom transfer radical polymerization (SI-ATRP), and all the PS brushes show smooth surfaces with roughness below 0.5 nm. Compared with frequently-used modified surfaces treated by UV/O3, HMDS and OTDS, PS brushes exhibit favourable modification and modulation for the crystallization of inkjet-printed single-droplet TIPS-pentacene film. As the thickness of PS brush increasing, TIPS-pentacene molecules aligned and crystallized more continuously with bigger crystal size. And on the PS brush of 15.0 nm thick, the continuous crystallization occurs within the whole size. The good crystallization of semiconductor molecules can be ascribed to the grafted long PS chains, which contribute a moderate viscosity for the deposited ink to produce a continuous crystallization. For the OTFTs with printed single-droplet TIPS-pentacene, the device performance also grows with the increasing of the PS brush thickness, and the PS brush of 15.0 nm thick induced the highest Au-electrodes OTFT mobility of 1.14×10-2 cm2 V-1 s-1.