Thermal Stability And Responsive Organic Thin Film Transistors:Materials Synthesis And Device Fabrication

Organic thin film transistors?OTFTs?have been widely investigated for a wide range of applications,both in terms of device structure and performance optimization.At the same time,the pursuit of multi-functional OTFT devices,in which organic phototransistors?OPTs?combine light detection and switching functions together have also been extensively focused.Organic materials,as a core part of an OTFT device,have been developed rapidly despite of various challenges,Various organic materials especially those based on small molecule derivatives of[1]benzothieno[3,2-b][1]benzothiophene?BTBT?core exhibited excellent semiconductor performance.However,the ability to maintain high mobilities at elevated temperature environments has been a huge challenge.However,small-molecule semiconductors based OPTs devices that can be used normally under high temperature conditions are rarely reported.The molecular structures developed in recent reports will have a significant impact on the device performance.The molecular structure of organic semiconductors can be designed to regulate the molecular energy level,and the molecular structure with a certain rigidity can result in a material with high thermal stability.At the same time,in some cases of thermal annealing,few molecules could form a bilayer structure and show better performance.Based on the recent research achievements reported in literature,it is necessary to simplify and design a more practical semiconductor material.Small molecule semiconductor materials designed for OTFTs and OPTs are mainly expected to have high mobility and high optical responsivity.From the point of view of selecting small-molecule organic semiconductor materials with characteristic light absorption,large planar structure and?-conjugated extension,highly ordered polycrystalline thin films can be deposited for their use in both OTFT and OPTs devices to achieve higher performance.In order to obtain high performance OTFTs and OPTs,in this work,we have designed and synthesized a class of BTBT-based dimer derivatives and BTBT derivatives containing azo structure by analyzing and summarizing related results.Two of the BTBT dimer derivatives,1,4-bis?[1]benzothieno[3,2-b][1]benzothiophen-2-yl?benzene?BTBT-Ph-BTBT?and 4,4'-bis?[1]benzothieno[3,2-b][1]benzothiophen-2-yl?-1,1'-biphenyl?BTBT-DPh-BTBT?,in which a similar bilayer structure?two BTBT-based monomer molecules linked by chemical bond?is combined with an extended?-conjugated structure,and their physicochemical characteristics and charge carrier transport properties are investigated.Compared with monomeric compounds,organic thin film transistors based on BTBT-Ph-BTBT and BTBT-DPh-BTBT show significantly higher mobility(up to 2.5 and3.6 cm²V^-1s^-1for BTBT-Ph-BTBT and BTBT-DPh-BTBT,respectively).When the devices based on these materials were thermally annealed at 350?,the mobility of the BTBT-Ph-BTBT-based OTFT is observed to be maintained at a high value of 2.4×10^-1cm²V^-1s^-1.In addition,OPTs based on BTBT-Ph-BTBT and BTBT-DPh-BTBT exhibited excellent photoresponse performance under illumination of low power intensity incident light in the range of 250-400 nm.This work provides a method to design active layer materials for high-performance and thermally stable OTFTs and OPTs.The results obtained in this work will pave a way to design and synthesize new materials which could also be suitable for future optoelectronic devices.