Inkjet printing of TiO2 potentially offers a high degree of control over the deposition of TiO2 suspensions. Previous use of inkjet printing for TiO2 depositions have focused on producing TiO2 films with uniform density. A multi-ink printing system offers the possibility of depositing TiO2 films with variable density using a single deposition method.
For this research, inkjet printing of TiO2 films with a graded density profile was explored as a means of improving dye sensitized solar cells (DSSCs) performance. Varying pore volume as a means to produce density variations in TiO2 layers was explored. To control the pore volume, several TiO2 suspensions were developed with different pore-forming additives. DSSCs with printed TiO2 films having three density layers showed an average improvement in the conversion efficiency of 127% versus those with a single layer and 45% versus those with dual- layer TiO2. Short-circuit current densities of cells with tri-layer films increased an average of 62% over those with a single layer and 17% over those with dual-layer TiO2. It was also shown that DSSCs with inkjet printed TiO2 layers performed better than those with spin-coated TiO2 layers.
The results effectively demonstrated the potential for using inkjet printing as a sole deposition method to produce TiO2 films with non-uniform density leading to improved DSSC performance. One possibility for further study is to create further layer variations through simultaneous printing of different suspensions.