Preparation And Properties Of Graphene-based Transparent Conductive Films

Flexible transparent conductive film has become a research hotspot in flexible electronics field due to its foldable,wearable,and low-cost process.Graphene,a mono atom layer of a two-dimensional(2D)carbon lattice,is considered to be an ideal material for flexible transparent conductive films due to its high electrical conductivity,optical transparency and excellent mechanical flexibility.However,graphene-based transparent conductive films are still facing high sheet resistance at relative high light transmittance due to the micro-nano structure defects and the like.Hence,this dissertation focused on transparent conductive films based on graphene oxide(GO)and graphene as raw materials.The composites of 2D graphene and 1D silver nanowires,carbon nanotubes were also prepared to fabricate transparent conductive films.The relationship between microstructures and macroscopic properties and their applications in flexible and wearable electronics of the transparent conductive films were further studied systematically.The main content is summarized as follows:(1)The GO thin film was synergistically reduced by a chemical method and 1100 ℃high temperature thermal reduction method.The GO thin film was first reduced by the vapor of hydroiodic acid and acetic acid mixture at 100 ℃ for 3 h and then reduced at 1100 ℃ for 0.5 h in an argon atmospheret to restore its sp2 structure.The obtained graphene-based transparent conductive film exhibited a resistance of 562 Ω/sq with a transmittance of 63.7%.The optoelectronic properties of the graphene-based transparent conductive film obtained by this method was better than those obtained by traditional chemical reduction method.(2)Mussel-inspired polydopamine-functionalized graphene was fabricated.Polydopamine functionalized graphene surface was rich in catechol groups,which enabled graphene to be adhesive.Polydopamine enhanced the interfacial interactions between graphene sheets and that between graphene sheets and the substrates.It also avoided the damage of the graphene films during the transfer process.(3)The 2D polydopamine-functionalized graphene was mixed with 1D high conductive silver nanowires to prepare transparent conductive films.Silver nanowires enhanced the conductivity of graphene based transparent conductive films effectively,and the polydopamine-functionalized graphene enhanced the adhesion force and oxidation resistance of silver nanowires.The transparent conductive film of polydopamine-functionalized graphene and silver nanowire composites was found to have a sheet resistance of 63 Ω/sq and a transparency of 70.5%.(4)A novel transparent conductive film with poly(3,4-ethylenedioxythiophene)/silver nanowires/polydopamine functionalized graphene sandwiched structure was fabricated.Multi-interfacial interactions between the top poly(3,4-ethylenedioxythiophene)and the underlying poly dopamine functionalized graphene as well as the capillary forces induced welding and fusion of the intermediate silver nanowires at low temperature.The sandwiched structure film exhibited a sheet resistance of 12.4 Ω/sq and a transparency of 89.6%.This method created the bases for large-scale and roll-to-roll process of flexible electronics.(5)Carbon nanotubes was used as the 3D conductive network to reinforce the framework and graphene was used as a patch of carbon nanotubes network.Poly(3,4-ethylenedioxythiophene)as a "cross-linker" of carbon nanotubes and graphene sheets to construct a 3D flexible conductive network.The conductive network was embedded into a flexible substrate derived from crab shells and potato.The transparent conductive film can disappear transiently.The biodegradable transparent conductive film exhibited a sheet resistance of 46 Ω/sq and a transparency of 83.5%,which provides a new way to solve the current serious e-waste problem effectively.In summary,this dissertation focused on the high-performance graphene-based transparent conductive film.We systematically studied the optoelectronic properties of pure graphene and its hybrids with 1D carbon nanotubes and silver nanowires based transparent conductive films.This systematic investigation would contribute to further development of novel graphene-based flexible and wearable optoelectronic devices.