Synthesis and direct ink writing of silver ink for fabricating current collecting lines of dye sensitized solar cells

Conductive gridline is essential part of electronic devices. Direct ink writing is fast and simple method for gridline deposition. In this work, silver ink suitable for direct ink writing was synthesized. Thereafter, the effect of writing process parameters was investigated. Then, silver conductive lines were deposited on electrodes of the dye sensitized solar cell (DSSC) by direct ink writing and its role in increasing the efficiency of DSSC was investigated.    

Silver ink was synthesized according to Lewis-Walker method. Silver acetate was dissolved in ammonium hydroxide and formic acid was added as reducing agent. The viscosity of ink was tuned by adding hydroxyethyl cellulose (HEC). Direct ink writing apparatus was built in our lab. Different ink writing process parameters were investigated. Photoanode and counter electrode of DSSC were fabricated on FTO substrates. Photoanode composed of N719 dye sensitized TiO2 nanoparticles and counter electrode consisted of platinum thin film. The distance between electrodes was filled by electrolyte. Finally, silver lines were written on electrodes of DSSC to obtain conductive gridlines.    

2.3 wt% HEC gave the best result. It was found that nozzle-substrate distance has no influence on shape and electrical resistance. However, at higher distances printed lines became disconnected. Width and thickness of silver gridline increased with injection rate and value of 0.48 ml/min was optimum value. Sintering at 360 ˚C was proposed for following steps. By applying silver gridlines on DSSC, fill factor and power conversion efficiency (η) increased significantly. η increased from 1.5% to 2.8%.