Screen printing of transparent conductive features based on silver nanowire networks

Abstract

Metal nanowire networks are a promising concept for replacing ITO in transparent electrodes for a range of optoelectronic devices. In these networks, the nanowires conduct charge carriers, while the open areas allow the transmission of light. Metal nanowires are both printable and achieve a performance equivalent to ITO upon thermal processing at temperatures below 150°C which make them ideal for depositing transparent electrodes on plastic substrates. For this contribution, silver nanowires (AgNWs) were synthesized using a polyol synthesis method. Various formulations containing AgNWs were prepared and their rheological behavior was assessed in view of screen printing. The most promising formulations were selected to print test features on PET substrates and the electrical and optical characteristics of these features were measured by a Van der Pauw method and UV-Vis spectroscopy respectively. By the addition of AgNWs to a PEDOT-based formulation, the sheet resistance of the printed features can be decreased from ca. 200 Ohm/sq to values below 40 Ohm/sq, indicating that a nanowire network improves the conductivity. However these features appear blue due to the absorption of (infra-)red light by PEDOT. The optical properties can be significantly enhanced by replacing the PEDOT-based formulation by a cellulose-based formulation.