The Effect of Improving the Ordering of P3HT Thin Films on the Performance of OFETs

The effects of three different boiling point solvents (chloroform $(60^{\circ}C)$, anisole $(155^{\circ}C)$ and o-dichlorobenzene $(180^{\circ}C))$ on the quality of P3HT thin films and the electrical characteristics of OFETs were investigated. And the surface of SiO 2 was modified with Hexamethyldisilazane (HMDS). The surface energy of modified SiO 2 decreased from 44J/cm2 to 23J/cm2. The number of leaf-like crystals on P3HT film increased and the size became larger. Then, 5% cyclohexanone was doped to P3HT solution in o-dichlorobenzene solvent to enhance the interaction force between P3HT molecular chains and make the polymer molecules tightly packed to form ordered aggregation. Finally, a certain amount of polystyrene (PS) was doped into the P3HT solution to produce OFET. The scanning pattern of confocal microscope showed that the number and size of leaf-like crystals on the film surface further increased when P3HT: PS = 10:1. In addition, the ultraviolet-visible light absorption spectrum, confocal microscope, and polarized microscope images showed that the order and crystallinity of the polymer molecules have been improved. The carrier mobility of the final device is increased to $1.05\times 10^{-1}$ cm2/Vs compared with the $7.06\times 10^{-2}$ cm2/Vs in basic experiment, and the threshold voltage is also reduced from 16V to 5V.