Research On Laser Preparation And Properties Of Ag Grid Transparent Electrodes With Different Shapes On Surfaces Of FTO Thin Films

Metal grid transparent electrodes are widely used in light-emitting diodes,solar cells,touch screens,liquid crystal displays and other photoelectric devices because of their good electrical conductivity,optical transmittance,good flexibility and easy access to raw materials.Also they are the best alternative to the indium tin oxide(TCO).With the increasing demand for the comprehensive performance of the metal grid transparent electrode,the preparation methods of the metal grid transparent electrode are being studied and innovated constantly.At present,the research on the grid pattern is mainly about the optimization of the grid shape,but there are few reports on the in-depth study of the optimal grid shape.Based on this,the grid shape was deeply explored in this paper,and the influences of laser parameter,grid shape and grid level for preparing an embedded metal grid on the comprehensive performance of the metal grid transparent electrode were studied.Some meaningful results were obtained as follows.1.A nanosecond pulsed laser(532 nm in wavelength)was used to perform laser etching on the FTO substrate with a spin coated PVP layer,and the effects of laser fluence and scanning speed on the width and depth of laser-etched grooves on the PVP/FTO substrate were systematically studied.It was found that when the scanning speed was 5–25 mm/s and the laser fluence was 1.2–2.8 J/cm²,laser etching could result in grooves with a width in the range of 23–31?m and a depth in the range of 1.02–1.14?m.When the scanning speed was10 mm/s and the laser fluence was 1.6 J/cm²,the width and depth of the resulting groove were respectively 23.82 and 1.02?m,and the groove quality was the best.2.Under the above optimal laser etching parameters(10 mm/s and 1.6 J/cm²),periodic grid grooves with different shapes were obtained on the PVP/FTO substrates by laser etching using the nanosecond pulsed laser(532 nm in wavelength).And 1?m-thick Ag thin films were then deposited on the PVP/FTO substrates by magnetron sputtering,followed by removal of the PVP/Ag by ethanol.The optical,electrical and comprehensive properties of the resulting regular periodic Ag grid transparent electrodes with different grid shapes were studied.The experimental results showed that when the circumradius was 0.75 mm,the regular periodic hexagonal Ag grid transparent electrode had the best optical transmittance,the strongest electrical conductivity and the highest comprehensive performance.The regular periodic triangular Ag grid transparent electrode had an average visible transmittance of71.68%,a sheet resistance of 2.73?/sq and a figure of merit of 1.31×10^–2?^–1.The regular periodic square Ag grid transparent electrode exhibited an average visible transmittance of73.15%,a sheet resistance of 2.33?/sq and a figure of merit of 1.88×10^–2?^–1.The regular periodic hexagonal Ag grid transparent electrode possessed an average visible transmittance of 73.91%,a sheet resistance of 1.89?/sq and a figure of merit of 2.57×10^–2?^–1.Subsequently,the performances of the regular periodic hexagonal Ag grid transparent electrodes with different circumradiuses were investigated.The experimental results indicated that when the circumradius was 1 mm,the as-obtained regular periodic hexagonal Ag grid transparent electrode had the highest comprehensive performance with an average visible transmittance of 78.11%,a sheet resistance of 2.31?/sq and a figure of merit of3.66×10^–2?^–1.3.Under the above optimal laser etching parameters(10 mm/s and 1.6 J/cm²)and circumradius(1 mm),fractal square grid grooves with different grid levels were obtained on the PVP/FTO substrates by laser etching using the nanosecond pulsed laser(532 nm in wavelength).And 1?m-thick Ag thin films were then deposited on the PVP/FTO substrates by magnetron sputtering,followed by removal of the PVP/Ag by ethanol.The optical,electrical and comprehensive properties of the resulting fractal square Ag grid transparent electrodes with different grid levels were studied.It was found that the level–3 fractal square Ag grid transparent electrode had the highest comprehensive performance with an average visible transmittance of 74.01%,a sheet resistance of 1.18?/sq and a figure of merit of4.18×10^–2?^–1.The average visible transmittance,sheet resistance and figure of merit of the corresponding regular periodic square Ag grid transparent electrode was 77.93%,2.55?/sq and 3.24×10^–2?^–1,respectively.The level–2 fractal square Ag grid transparent electrode displayed an average visible transmittance of 76.03%,a sheet resistance of 1.96?/sq and a figure of merit of 3.29×10^–2?^–1.Subsequently,the performances of the level–3 fractal Ag grid transparent electrodes with different shapes were investigated.The experimental results indicated that the fractal triangular Ag grid transparent electrode had an average visible transmittance of 73.21%,a sheet resistance of 1.53?/sq and a figure of merit of 2.89×10^–2?^–1.The fractal square Ag grid transparent electrode exhibited an average visible transmittance of 74.01%,a sheet resistance of 1.18?/sq and a figure of merit of 4.18×10^–2?^–1.The fractal hexagonal Ag grid transparent electrode possessed an average visible transmittance of 75.03%,a sheet resistance of 1.21?/sq and a figure of merit of 4.67×10^–2?^–1,indicating the best comprehensive performance.