银纳米线柔性可见光透明电极的制备与研究（特邀）

In recent years， wearable electronic devices have attracted significant research interest. With the rapid development of the new generation of electronic devices， high-performance flexible transparent electrode is desired to realize high-efficient and high-performance optoelectronic devices. A flexible transparent electrode is a kind of conductive film which has ultra-high conductivity and transmittance. In addition to these two important features， a new generation of flexible transparent electrodes must exhibit good mechanical flexibility. They have various applications such as flexible solar cells， smart glasses， flexible sensors， tactile electronic skin， and flexible displays， which changes and improves our daily life. The most widely used transparent electrode material is Indium Tin Oxide （ITO）， which has high transmittance （>90%） under low sheet resistance （10 Ω/sq）. However， ITO has many disadvantages， such as poor adhesion to substrate， inherent brittleness and high price， which is not suitable to fully meet the requirements of flexible electronic devices. Researchers have explored some new transparent electrode materials to replace the traditional ITO electrodes， such as conductive polymers， graphene， carbon nanotubes， metal grids， metal nanowires， and so on. Among them， silver nanowires are regarded as the most promising conductive materials due to their excellent optoelectronic properties and mechanical flexibility. However， the silver nanowires network has a high contact resistance due to the weak contact at the junctions， which causes poor conductivity and weak contact. Mechanical stability and the electrical conductivity can be improved by melting and welding the silver nanowire network. The traditional thermal annealing welding process is time-consuming， and the required high temperature （above 200°C） can easily destroy the silver nanowires and flexible substrate. In this paper， a new method was developed to achieve high-efficient welding of silver nanowire networks at low temperatures using the optical nano-welding process. Silver nanowires/PMMA/PDMS flexible transparent electrodes were fabricated combined with the femtosecond laser nano-welding process. Numerical simulations of the interaction between different silver nanowire crossing angles at different laser wavelengths were performed， and the optimal conditions for laser welding and silver nanowire solutions were explored. The results showed that the silver nanowires network structure has strong absorption in the laser wavelength range of 500~600 nm. The effects of laser wavelength， laser energy and irradiation time on the sheet resistance of the film were studied. The results showed that when the laser power used was 160 mW， the sheet resistance of the thin film can reach the lowest value at a shorter irradiation time （25 s）. In addition， from the microscopic morphology of the silver nanowire junction， only the junctions of silver nanowires were melted and welded during the laser irradiation， while the remaining structure was not affected or even damaged including the flexible substrate. The highest figure of merit was also obtained when optimizing the deposition density of silver nanowires. When the deposition density of silver nanowires was 167.85 mg/cm²， the optimal sheet resistance value of the flexible transparent electrode was 12.72 Ω/sq， with a transmittance of 82.41% at 550 nm wavelength， demonstrating excellent optoelectronic properties. The proposed flexible transparent electrode also showed good mechanical stability， and the sheet resistance of the silver nanowire flexible transparent electrode remained relatively stable over 220 bending cycles and 70 adhesion tests. This remarkable feature paves the way for a new generation of flexible wearable electronics in the future.