Low-temperature versus oxygen plasma treatment of water-based TiO2 paste for dye-sensitized solar cells

Abstract

High-temperature treatment steps in fabrication process of dye sensitized solar cell (DSSC) significantly contribute to the manufacturing costs and limit the use of temperature sensitive substrates. Therefore our aim was to develop a simple method for the preparation of water-based TiO2 paste. The paste is based on peroxotitanic acid (PTA) sol–gel matrix and commercial TiO2 nanoparticles (P25). Two fabrication processes to decompose/transform the PTA matrix in the printed TiO2 layer are explored and combined: annealing at temperatures up to 250 °C and/or oxygen plasma treatment. The results show that the PTA matrix in the paste converts to anatase phase and to some extent also attaches to the TiO2 nanoparticles P25 acting as an interconnecting network within TiO2 layer. The transformation of the PTA matrix occurs around 250 °C, but in the presence of TiO2 nanoparticles P25 it starts already at 120 °C. In addition the results reveal that the crystallization is achievable also solely with the oxygen plasma treatment. The efficiency of the TiO2 layers, exposed to different post-deposition treatments, is evaluated in DSSCs. The results show that oxygen plasma treatment of the TiO2 layers could efficiently replace temperature curing at 250 °C. Within this study the DSSCs with the efficiency up to 4.2 % measured under standard test conditions (1,000 W/m2, AM1.5, 25 °C) were realized.