Light management in dye-sensitized solar cell

Abstract

Dye-sensitized solar cell (DSSC) is composed of a nanocrystalline TiO2 film whose surface is covered with dye molecules, an iodide/tri-iodide electrolyte and a platinum counter electrode. Charge generation occurs when dye absorbs photon energy, which is separated by injection of photo-excited electrons into the conduction band of TiO2. The photo-injected electrons are transported through TiO2 network and collected at transparent conducting electrode. The oxidized dyes are regenerated by oxidation of iodide. Light-to-electricity conversion efficiency depends on photocurrent density, open-circuit voltage and fill factor. Photocurrent density is related to the incident photon-to-current conversion efficiency (IPCE) that is a collective measure of light harvesting, charge separation and charge collection efficiency. Since the higher IPCE, the higher photocurrent density becomes, light management in DSSC is one of most important issues. In this paper, effective methods to improve IPCE are described including size-dependent light scattering effect, bi-functionality design in material synthesis and panchromatic approach such as selective position of different dyes in a mesoporous TiO2 film.