(Invited) A Systems View of Solar Energy Conversion Efficiency in Dye-Sensitized Photoanodes

Abstract

Dye-sensitized photoelectrodes are highly complex structures, involving large internal surface areas hosting tightly coupled interfacial and electrolyte chemistry. How the electrode architecture and the chemical reactions in them are connected to measured photovoltages and photocurrents for the simplest case of the dye-sensitized solar cell is examined using full-system multiscale reaction-diffusion simulations. These calculations provide a fully spatially resolved time history of the system, spanning nm-microns and ns-sec. In this talk, a basic but physically realistic computational framework will be introduced, and several aspects of system behaviors revealed by the simulations will be described. The influence of molecular diffusion on photocurrents, within the photoelectrode and across the system, will be described. Whether electron-electrolyte recombination within the photoanode is responsible for losses that limit efficiency is also examined. Recombination reactions are found to be significant, but are not performance-limiting because the reactions drive shifts in the electrolyte chemistry to support efficient dye cycling, and compensate for losses. This phenomenon can compensate for efficiency limitations due to diffusion between the photoanode and the cathode. The implications of these findings for strategies to improve the efficiency of this class of systems are discussed.