Meter-scale Carbon Nanotube Thin Films And Their Applications In Transparent Thin Film Transistors

Single-wall carbon nanotubes(SWCNTs)have been considered one of the most promising candidates for flexible and transparent electronic devices due to their extraordinary electrical,mechanical and optical properties.SWCNT films have been demonstrated as both promising transparent electrodes and semiconducting active channels in various flexible and transparent electronics.The production of high-quality SWCNT thin films by an efficient and scalable method has become a key issue for their practical application in flexible electronics.However,the size of fabricated SWCNT films is usually limited to be in a square centimeter scale,and the batch processing used is not scalable.Besides,the optoelectrical performance of SWCNT films is far below theoretical predictions,due to the impurities and structural defects introduced during the solution processes of film fabrication.In this dissertation,we propose a continuous synthesis,deposition and transfer method for the fabrication of high-quality SWCNT thin films.A meter-scale SWCNT thin film with high performance has been prepared continuously for the first time,which demonstrates wide-range applications of SWCNT thin films in large-area,flexible and transparent electronics.(1)A gas-filtration method was proposed to continuously deposite SWCNTs on a membrane filter and meter-scale,uniform SWCNT films with controllable densities were obtained at room temperature and atmospheric pressure.SWCNTs were continuously synthesized by a floating catalyst chemical vapor deposition technique and then deposited onto the membrane filter in a self-made gas filtration system.A fluid dynamics simulation of the gas velocity distribution in the gas-filtration system showed a uniform velocity distribution in the gas stream at the equilibrium state,indicating that a steady and uniform SWCNT deposition process was possible.The as-deposited SWCNT films were transferred onto flexible polymer substrates with the aid of a roll-to-roll transfer technique,and SWCNT films with a width of 0.5 meters and unlimited length were obtained for the first time.(2)The as-prepared SWCNT films exhibited excellent optoelectrical performance and uniformity.SWCNT films had a transmittance of 90%at a wavelength of 550 nm and a sheet resistance of 65 ?/? and the relative standard deviations of the corresponding transmittance and sheet resistance were 0.3%and 7.4%,respectively.(3)High perfonnance CNT thin film transistors(TFTs)were fabricated by adjusting the density of CNT films.The as-fabricated CNT TFTs show a carrier mobility of 76 cm2V-1S-1 and on-off current ratio of 106.Large-area,high-performance all-carbon flexible and transparent TFTs and integrated circuits,including inverters,NAND/NOR/XOR logic gates,ring oscillators and active-matrix organic light emitting diode driving circuits,were fabricated on flexible substrates by using SWCNT films with different densities as flexible electrodes,interconnects and semiconductor channel materials.These results demostrate that SWCNT films are promising for use in large-area,flexible and transparent electronics.