Enhanced photovoltaic performances of dye-sensitized solar cell using self-charring phosphate ester surfactant

In this article, we describe the use of Triton™ X-based surfactants with an octyl phenol ethoxylate (OPE) backbone and a phosphate ester chain end as a dispersant for formulating TiO2 paste. Three phosphate-terminated Triton™ X (or OPE) derivatives, i.e. [OPE2-OPO(OH)2], [OPE5-OPO(OH)2], and [OPE10-OPO(OH)2] are prepared from OPEs of different oxyethylene units and phosphorous pentoxide. The phosphate-terminated Triton™ X of the highest number of oxyethylene units (i.e. OPE10-OPO(OH)2) provides the desirable amount of char (9 wt.%) at 600 °C under air atmosphere, and is found to lower the viscosity of [TiO2/ethyl cellulose/terpineol] paste, leading to finer and more close-packed TiO2 film after firing. The photoanode film prepared by the TiO2 paste was built up on a conducting glass plate by a screen printing process followed by a heat treatment for sintering. Then, the TiO2 film showed not only higher particle density, but also residual char on the particle surface in comparison with the control sample film prepared from the [TiO2/ethyl cellulose/terpineol] paste with no dispersant. The dye-sensitized solar cell (DSSC) employing the prepared nanocrystalline TiO2 film with char exhibits significantly improved photovoltage and photocurrent characteristics under 1 sun illumination.