Orientation Mechanism Of Organic Semiconductor In Solution And Characterization Of Its Films Morphology

Organic thin film transistors (OTFTs) prepared by solution method with the advantages of low cost and environment-friendliness have become research hotspot at present. The dip-coating and inkjet printing technology for OTFTs have attracted much attention because of its large area orientation and digital direct writing patterned film forming in recent years. Based on dip-coating and inkjet printing technology, we mainly investigated the growth mechanism of organic semiconductor molecules in solution and their film characterization. Then, we further studied properties of OTFT devices. The main contents are as follows:(1) The mechanism of the direction growth films prepared by dip-coating technology was films are controlled by the capillary flow in the specific direction of the solution.That was compatible with mixed ink, and the coverage of the film was proportional to the viscosity of the solution. In addition, the oblique 20 scanning mode was proposed to represent the in-plane texture of the 6,13 bis(tri-isopropylsilylethynyl)Pentacene (TIPS-pentacene) crystal, and the crystal lattice of the films prepared by dip-coating from the higher viscosity chloroform solution have larger angle of a, smaller y, and the lattice constant b, the device exhibits a mobility of up to 1.5 cm2V-1s-1.(2) Substrate with asymmetric structure across microscale profiles were designed and fabricated, which constitute a mechanism for directional crystallization by applying asymmetric capillary forces on the deposited precursor solution of TIPS-pentacene, i.e.forming a gradient of surface energy on the fluidic surface, and then the organic semiconductor emerged direction growth and self-alignment effect. Average mobility of arrayed OTFTs obtained via this method was increased by 40 % while the relative standard deviation (RSD) was reduced from 68 % to 39 %. It can satisfy arrayed OTFTs with the semiconductor layer grown via this method realized directional crystallization of organic semiconductor across microscale surfaces, and showed increased field-effect mobility and improved performance uniformity.(3) The active layer based on the 2,7-dioctyl[1]benzothieno[3,2-b][1]Benzothiophene (C8-BTBT) material for OTFT was fabricated by the inkjet printing technology. High-performance devices were obtained by optimizing the drop space and temperature of the substrate (Saturated field-effect mobility is 1 cm2V-1s-1 the on/off ratio of the OTFT achieved over 106). Experimental results indicated that the highest performance of OTFT device obtained on the poly-4-vinyl phenol (PVP) or phenethyltrichlorosilane (PETS) substrates possessed good uniformity, high coverage and orderly crystalline films due to hydrophobicity and relatively flat surface of substrates.The fabricated OTFT on PVP substrate have stable performance was proved by the negligible changes of saturated field-effect mobility after the device delayed 40 days(Saturated field-effect mobility was holding at 1 cm2V-1s-1, the on/off ratio was still over 106).