Transparent Conformal Electrode And Its Application In Organic Transistor

With the rapid development of wearable and portable electronics,electronic devices will evolve from the current rigid systems to flexible systems and ultimately to stretchable electronics,enabling true seamless integration of electronics with biology.Transparent conformal electrodes are of great significance for the future development of electronic skin and other frontier technologies.Recently transparent stretchable electrodes have made some progress.However,the high-precision pattern of transparent stretchable electrode is still a challenging task to accomplish,which is directly responsible for the integration and photoelectric properties of the device.Organic field-effect transistor(OFET)has the advantages of light weight,inherent mechanical flexibility,and can maintain the stable electrical properties under mechanical deformations.Therefore,combining organic field-effect transistor with transparent conformal electrode will play a strong role in future flexible/elastic bionic electronics.In this dissertation,we fabricated the transparent confofomal electrodes with high-precision via photolithography,and obtained the high-performance transparent conformal organic field-effect transistors.The main results are as follows:1.The conformal electrodes with high-resolution pattern and good mechanical flexibility were obtained based on photolithography method and embedded structure.Based on the high-resolution patterned electrodes,we explored the anisotropic transport in one-dimension organic single-crystal microbelt by a “cross-channel” method.The rubrene microbelt showed the highest mobility up to 26 cm2/V·s in the length direction.To the best of our knowledge,this is the highest value for rubrene OFETs to date.Based on the conformal electrodes and flexible rubrene microbelt,the conformal organic field-effect transistor was fabricated by layer-by-layer assembly.Furthermore,the organic circuit with good adherence on a pearl ball was realized.These results present great potential for the applications of conformal electrodes in the next-generation conformal electronics.2.To improve the transparency of the conformal electrode,ultrathin embedded metallic grid electrode was obtained via photolithography.The metallic grid electrode showed the high transparency of 90%,and the sheet resistance was 70 ?/?.Fully transparent conformal organic thin-film field-effect transistor array was demonstrated based on the photolithography-compatible ultrathin metallic grid electrode and the solution-processed C8-BTBT film.The resulting organic field-effect transistor array exhibited high optical transparency of >80% over the visible spectrum,mobility up to 2 cm2/V·s,on/off ratio of 105~106,switching current of >0.1 m A,excellent mechanical stability and light stability.The transparent conformal transistor array was demonstrated to well adhere onto the flat and curved LEDs as front driving.These results open a path towards applications of the solution-processed transistors in future large-scale transparent conformal active-matrix displays.3.To further improve the mechanical property of the electrode,PEDOT:PSS/SWCNTs composite electrode was fabricated to replace the thermal-evaporated metal electrode by an all-solution method.The transmittance of ultrathin composite electrode(25 nm)was 83% at 550 nm,and the sheet resistance was 90 ?/?.In addition,the composite electrode could stretch up to 280%,and withstand the mechanical deformations of twist,roll,stretch and wrinkle.Based on the photolithography method,the transparent stretchable electrode with high precision pattern could be achieved,and the pattern precision was up to 3 ?m.To the best of our knowledge,3 ?m is the highest precision pattern for the reported transparent stretchable electrodes.The all-solution-processed organic thin-film field-effect transistor was obtained by layer-by-layer assembly.The resulting organic field-effect transistor array exhibited high optical transparency of >80% over the visible spectrum,mobility up to 2.7 cm2/V·s,average mobility of 1.2 cm2/V·s.The transparent conformal transistor could be attatched on the uncommon surface and applied in the LED drive circuit.These results present the great potential of the transparent conformal organic transistors in the next-generation wearble electronics.