Preparation And Photoelectric Properties Study Of OFET Based Polymer/Small Molecules

As one of the important components of optoelectronic devices,organic field-effect transistors（OFETs）are widely used in radio frequency identification tags,sensors,flexible electronic displays and other fields,and have been the focus of researchers.Organic polymers have the natural advantages of being easy to process in solution,flexible and mass-producible,making them ideal candidates for the construction of high-performance organic field-effect transistors.However,limited by the complexity of the transport excitation mechanism of polymer semiconductors and the difficulty of tuning their multilayer condensed state structure,the mobility of polymer-based organic field effect transistors has so far been relatively low and the functionality is relatively homogeneous.Research into the structure-property relationship of organic semiconductors is of great importance as a guide to the realisation of good stability,high mobility and versatile OFET devices.By selecting the blended system of organic small molecules and polymers as the sample,this dissertation has concentrated on the controllable preparation of organic crystalline structures and the optoelectronic performance of their corresponding devices,systematically exploring the crystalline behavior of the blend of organic small molecules and polymers,the optoelectronic characteristics and the mechanisms.The specific research contents include the following two aspects:（1）Crystalline structures with controllable morphologies were prepared by solution crystallization by blending small molecule TIPS with polymers PBTTT and F8BT,respectively.The blend system of TIPS/PBTTT via crystallization can overcome the poor solution processability of small molecules and the inferior crystalline properties of polymers,achieving fiber crystals with uniform orientation and large area.The corresponding device had a mobility of up to 0.3 cm² V^-1 S^-1,showing good stability.Based on the solution crystallization of TIPS/F8BT,an ultra-thin rod-like crystal structure with a regular shape was obtained,yielding the mobility of around 3.6 cm² V^-1 S^-1.The mobility of microcrystals was much higher than that of the corresponding crystalline films.Based on the simple crystalline growth via solution-processed methods,the preparation of OFETs with high mobility and good stability was realized.（2）Bottom-gate top-contact organic thin-film transistors（OTFTs）based on photochromic molecules/polymers were prepared by introducing the photochromic molecules such as SP or DAE into the PBTTT active layer,respectively.OTFTs based on SP/PBTTT and DTE/PBTTT were stimulated by UV light.In this case,the leakage current of the devices increased significantly,but the threshold voltages showed an opposite trend.Therefore,great efforts were exerted on their optoelectronic properties.This phenomenon is mainly attributed to the reversible conversion of isomers of photochromic molecules under light stimulation,which produced energy changes in the process,thus leading to the reversible regulation of the electrical properties of the device.Organic electronic devices with optical switching function were prepared by adding photochromic molecules into polymers,which can provide an important foundation for multifunctional integrated devices.