Growth Of Ultra-thin Low-dimensional Organic Crystals By Dip-coating And Its Application

In the last years,low-dimensional structures based on small organic semiconductor materials have been of great interest,due to their different electronic and optical intrinsic properties from their polymers and inorganic counterparts.Low-dimensional structures of small organic semiconductor are easy to fabricate.They exhibit good molecular and electronics versatility,compatibility with flexible and substrates,solution-processable,low-cost and large-area fabrication.They can be integrated in miniaturized devices and are ideal materials in flexible electronics and printed electronics.But controllable growth of low-dimensional small organic crystals is still a great challenge,and study on the relationship with their structures and properties is just in infancy.Thus,it is significant to realize controllable growth of low-dimensional organic crystals and explore their properties both in fundamental research and practical application.In this thesis,based on different alkanes as small organic molecules and Thiophene and benzene polycyclic molecules(TF)with different alkyl chain length as organic semiconductor molecules,we have realized controllable growth in low-dimension by dip-coating method.At the same time,we focus on the study of their structures and optoelectronic properties:1.We study building low-dimensional structure of alkanes molecules with different length of carbon chain using dip-coating method.Finally,we got one-dimensional stripe structures of dotriacontane and ultra-thin two-dimensional organic crystals of tetratetracontane.For these organic crystals,we used a necessary morphology and structure characterization.Then we used one-dimensional stripe films of dotriacontane and micro-crystal thin films of tetratetracontane as the template layer to induce growth of organic semiconductor molecules such as pentacene,6,13-bis(tri-isopropylsilylethynyl)pentacene(TIPS-pentacene),2,7-dioctyl benzothieno [3,2-b] benzothiophene(C8-BTBT).In order to further study the electronic properties of organic semiconductor thin film obtained by the template method,we constructed the field effect transistor based on pentacene/alkane with a bottom-gate and top-contact structure.Experimental results show that device performance based on template-induced pentacene is superior to the traditional pentacene device,mobility increased to 0.49 cm2 / V·s from 0.064 cm2 / V·s,owing to the decreasing of screw dislocation defects and passivation of the dielectric surface.2.Based on small organic semiconductor molecules TF-C6 and TF-C12,We study on the controllable growth of low-dimensional organic crystals using dip-coating method by controlling the concentration of the solution,type of solvent and lifting rate.Experimental results show that due to different solubility of this two molecules,they formed different low dimensional structure under different lift rates.Morphology of TF-C6 from stripes thin films transfer to long line crystals with the decrease of pulling rate;TF-C12 can form micro organic single-crystal under the high concentration of solution and low speed.In order to further study their electrical performance,we constructed bottom-gate and top-contact field effect transistor,results show that the device performance based on one-dimensional nano-stripes of TF-C6 is superior to the thin film transistor by physical vapor deposition method.