Performance Enhancement of Silver Nanowire-Based Transparent Electrodes by Ultraviolet Irradiation

Silver nanowires (AgNWs) are used as transparent electrodes (TE) in many devices. However, the contact mode between the nanowires is the biggest reason why the sheet resistance of silver nanowires is limited. Here, simple and effective ultraviolet (UV) irradiation welding is chosen to solve this problem. The influence of the power density of the UV irradiation on welding of the silver nanowires is studied and the fixed irradiation time is chosen as one minute. The range of the UV (380 nm) irradiation power is chosen from 30 mW/cm² to 150 mW/cm². First of all, the transmittance of the silver nanowire film is not found to be affected by the UV welding (400-11,000 nm). The sheet resistance of the silver nanowires decreases to 73.9% at 60 mW/cm² and increases to 127.6% at 120 mW/cm². The investigations on the UV irradiation time reveal that the sheet resistance of the AgNWs decreases continuously when the UV irradiation time is varied from 0 to 3 min, and drops to 57.3% of the initial value at 3 min. From 3-6 min of the continuous irradiation time, the change of the sheet resistance is not obvious, which reflects the self-limiting and self-termination of AgNWs welding. By changing the wavelength of the UV irradiation from 350-400 nm, it is found that the welding effect is best when the UV wavelength is 380 nm. The average transmittance, square resistance, and the figure of merit of the welded AgNWs at 400-780 nm are 95.98%, 56.5 Ω/sq, and 117.42 × 10^-4 Ω^-1, respectively. The UV-welded AgNWs are also used in silicon-based photodetectors, and the quantum efficiency of the device is improved obviously.