Inkjet Printing of Titanium Dioxide Photoanodes for Dye Sensitized Solar Cells

Abstract

Dye Sensitized Solar Cells (DSSC) offer advantages over semiconductor solar cells including lower costs and relaxed material purity requirements. However, DSSC solar energy conversion efficiencies are lower than many competing photovoltaic technologies. Key to DSSC performance is the incorporation of nanocrystalline metal oxides to provide a large surface area for photosensitive dye loading. Titanium dioxide (TiO 2 ) is the predominately used metal oxide.The structure of the TiO 2 layer determines charge transfer efficiency and the level of generated photocurrent. Common practice for high performance cells is to deposit a thin, compact TiO 2 coating followed by a thicker, more porous TiO 2 layer. Often, different deposition methods are used for each layer.Inkjet printing of TiO 2 potentially offers a high degree of control over the deposition of TiO 2 suspensions. Previous use of inkjet printing for TiO 2 depositions have focused on producing TiO 2 films with uniform density. A multi-ink printing system offers the possibility of forming TiO 2 films with variable density using a single deposition method.For this research, inkjet printing of TiO 2 films with a graded density profile was explored as a means of improving DSSC performance. Cell performance was assessed through the measurement of generated currents and device Fill Factors.Two means to produce density variations in TiO 2 layers were explored: TiO 2 particle size and layer pore-volume. For the former, the reduction of micron-sized TiO 2 particles using a milling approach was attempted but proved unsuccessful. To affect changes in pore-volume, several TiO 2 suspensions were developed with varying pore-forming content that successfully produced variations in layer density. DSSCs with printed TiO 2 films having three density layers showed an average improvement in the Fill Factor of 8% versus single layers and 6% versus 5 double layers. Short-circuit currents in tri-layer films increased an average of 35% over single layers and 13% over double layers.The results effectively demonstrated the potential for using inkjet printing as a sole deposition method to produce TiO 2 films with a non-uniform density leading to improved DSSC performance. One possibility for further study would be to create further layer variations through the simultaneous printing of different suspensions.

Efficiency of inkjet printing in fabrication Organic Solar cells

“…Once the concentration reached 50%, the drop was more uniform in distribution but often exhibited weak adhesion to the substrate near the edges. Based on the observations, a concentration between 45 and 50% of PEG relative to the weight of the TiO2 was used for all suspensions prepared for deposition by printing and spin coating (Johnson 2013)…”

The role of printing techniques for large-area dye sensitized solar cells

“…In DSSC this technique has been mainly used to print patterned TiO 2 layers for both rigid and flexible (PET/ITO) substrates [124]. The inkjet is effective in multilayer deposition [125] where a multi-ink printing system offers the possibility of depositing TiO 2 films with variable density using a single deposition method.…”