FLUORINE-DOPED TIN OXIDE AEROGEL AS CONDUCTIVE SCAFFOLD FOR TIO2 IN DYE-SENSITIZED SOLAR CELLS

摘要

Nano-structured semiconductor materials are currently being explored in the dye-sensitized solar cell (DSC). Nanotube, nanowire and nanorod structures have been suggested to have enhanced photoelectrochemical properties [1]. These structures are expected to have faster electron transfer [2]. A drawback of these structures, however, is their relatively low surface area, which translates into lower dye adsorption and thus lower currents. Aerogels have recently been used as photoanodes in the DSC and are attractive structures due to their high surface area, high porosity and particle interconnectivity. They are made via sol-gel synthesis and supercritical drying (Figure 1). The solutions are processed as gels where the precursor particles are arranged in a three dimensional array with the solvent supporting the structure [3]. Evaporating away the solvent would result in high surface tension at the liquid-gas interface, leading to collapse of the structure. Instead, the gel is dried supercritically, allowing the solvent to escape while preserving the structure. To achieve supercritical phase change, the samples are placed in a pressurized autoclave and temperature is ramped-up above the critical point. The supercritical fluid is then slowly released, removing the solvent while leaving the gel structure intact, resulting in an aerogel [4].