| In recent years,with the continuous progress of science and technology and the development of new technology,people have put forward higher requirements for the quality of life and survival level,flexible electronic devices have entered the stage of rapid development.The development of flexible transparent electrodes with excellent light transmittance and electrical conductivity as well as excellent mechanical flexibility and their application in flexible optoelectronic devices and smart wearable devices is a promising research direction.It is very important and crucial to improve the conductivity of flexible transparent electrodes under the premise of making them have excellent light transmittance.Indium tin oxide（ITO）films have been widely used in commercial applications over the past half century due to their excellent compatibility with electrical conductivity and transparency.However,the drawbacks of ITO,such as the brittleness,the high temperature deposition process as well as expensive price,has severely limited the development of flexible transparent electrodes.In this paper,the flexible transparent electrode was constructed by depositing nano-conductive materials on the surface of the flexible substrate,and the application of bio-polysaccharide fiber in the field of flexible transparent electrode was explored,and the transparent electrode was combined as transparent capacitance sensor.The transmittance,conductivity,flexibility,stability,durability,interfacial adhesion of transparent electrodes as well as the capacitance sensing performance,durability,and signal monitoring performance of transparent capacitance sensor are tested.The main research contents are as follows:（1）In order to prepare flexible transparent electrode with good electrical conductivity and light transmittance,transparent polyethylene terephthalate（PET）film was used as flexible transparent electrode substrate,and metal carbide/nitride（MXene）conductive material was sprayed on the transparent substrate to construct conductive layer.The flexible transparent electrode has excellent flexibility and is combined as a flexible transparent capacitance sensor for human body signal detection.The photoelectric performance of the transparent electrode is good,and the sheet resistance can reach 200Ω/sq after being sprayed for many times,and its transmittance at 550 nm is 60%.The resistance of the flexible transparent electrode is almost unchanged during a single large-angle bending process,and the R/R0 only increases by5%after 1000 bending cycles,indicating that the flexible transparent electrode has good flexibility,stability and durability.During the adhesive strip test,the resistance increases greatly and the interface adhesion is poor.With the change of pressure,the relative capacitance of the flexible transparent capacitance sensor can be more than 65%,which has good sensing performance and transparency.TheΔC/C0 of the flexible transparent capacitive sensor remains stable after 1000 pressing cycles,which proves its good pressing durability.（2）In order to further improve the comprehensive properties of light transmittance and conductivity of the prepared transparent electrodes,and improve the adhesion of conductive materials on the surface of flexible substrates.The plant leaf vein fibers with continuous network structure were used as the flexible substrates of transparent electrodes by pre-template method,and MXene nanomaterials are deposited on the plant leaf vein network to form a continuous and uniform conductive network structure.The surface of the vein fiber is rich in hydroxyl active groups,and the surface of the MXene nanomaterial is also rich in hydroxyl active groups.The hydrogen bond formed between the two can effectively improve the deposition adhesion of the MXene lamella on the vein network.There are grooves on the surface of plant leaf vein fibers,and MXene nanomaterials are deposited along the grooves to improve the adhesion of nano-conductive materials on the surface of leaf vein fibers.This chemical functional group and physical structure have unique advantages,so that MXene conductive material and vein fiber interface has good adhesion.When the MXene is deposited on the vein network substrate for many times,the sheet resistance can be reduced to 11.4Ω/sq,and the transmittance at 550 nm is 80.6%,indicating good photoelectric comprehensive performance.In a single large-angle bending process,the resistance is almost unchanged,and R/R0only changes 4.6%after 1000 bending cycles.Its flexibility,stability and durability are relatively excellent.The resistance increase of adhesive tape is small and the interface adhesion is good.The transparent capacitance sensor is composed of flexible transparent electrodes prepared by MXene nanomaterial.The relative capacitance increases regularly with the increase of pressure,and the range of relative capacitance can reach more than 80%.After1000 press/release tests,ΔC/C0 remained stable,indicating excellent sensing performance,transparency and durability of the transparent capacitance sensor.（3）In order to further improve the photoelectric comprehensive performance of the transparent electrode and keep the light transmittance and conductivity of the prepared transparent electrode at a high level,silver nanowires（Ag NWs）and MXene were deposited on the surface of the plant leaf fiber to construct a three-dimensional conductive network,which greatly improved the stability of the conductive network.The one-dimensional Ag NWs continuous network is used as the architectural framework of the two-dimensional MXene sheets to provide a“high-speed conductive channel”for the conductive network of the MXene unit,and the MXene sheets are attached to the Ag NWs conductive network to form a stable three-dimensional conductive network.The three-dimensional conductive network flexible transparent electrode has a square resistance of 0.5Ω/sq when the transmittance at 550 nm is81.6%,and the overall optoelectronic performance is excellent.The resistance is almost unchanged during a single large-angle bending process,and the resistance increases by only0.11%after 2000 cyclic bending tests,showing good flexibility,cycle stability and durability.The resistance of adhesive tape increases very little and the interface adhesion is excellent.The relative capacitance variation range of the capacitive sensor prepared by the transparent electrode can reach more than 100%,almost no change after 2000 cycles,and can be used for signal monitoring,with good sensing performance,transparency and durability.In conclusion,the flexible transparent electrode with fiber conductive network structure was constructed by using bio-polysaccharide leaf fiber as flexible substrate,which has good light transmittance and electrical conductivity,and exhibits good flexibility,stability,durability,and interfacial adhesion.Its application in the field of wearable capacitive sensor was explored.The flexible transparent capacitive sensor prepared showed good transparency,sensing performance and stability,which can be used for human body signal monitoring.The flexible transparent electrode was prepared as a variety of flexible transparent devices,which greatly expanded the application of bio-polysaccharide vein fiber in the photoelectric field. |
