Invisible metal-grid transparent electrode prepared by electrohydrodynamic (EHD) jet printing

Invisible Ag-grid transparent electrodes (TEs) were prepared by electrohydrodynamic (EHD) jet printing using Ag nano-particle inks. Ag-grid width less than 10 μm was achieved by the EHD jet printing, which was invisible to the naked eye. The Ag-grid line-to-line distance (pitch) was modulated in order to investigate the electrical and optical properties of the EHD jet-printed Ag-grid TEs. The decrease in the sheet resistance at the expense of the transmittance was observed as the Ag-grid pitch decreased. The figure of merit of Ag-grid TEs with various Ag-grid pitches was investigated in order to determine the optimum pitch condition for both electrical and optical properties. With the 150 μm Ag-grid pitch, the EHD jet-printed Ag-grid TE has the sheet resistance of 4.87 Ω sq^-1 and the transmittance of 81.75% after annealing at 200 °C under near-infrared. Ag filling factor (FF) was defined to predict the electrical and optical properties of Ag-grid TEs. It was found that the measured electrical and optical properties were well simulated by the theoretical equations incorporating FF. The EHD jet-printed invisible Ag-grid TE with good electrical and optical properties implies its promising application to the printed optoelectronic devices.