Photoinduced absorption spectroscopy as a tool in the study of dye-sensitized solar cells

Photoinduced absorption spectroscopy, where the excitation is provided by a square-wave modulated (on/off) monochromatic light source, is a versatile tool in the study of dye-sensitized solar cells. Spectra of transient species, such as the oxidized dye, can easily be obtained and their kinetics can be explored using frequency or time-resolved techniques. Exptl. photoinduced absorption conditions can be kept close to typical solar cell operating conditions, allowing extn. of relevant time consts. Photoinduced absorption is also a suitable method to study the quality of pore filling in case of solid hole conductors. Dye mols. that are not in direct contact with the hole conductor will have long lifetimes in their oxidized state and appear clearly in the photoinduced absorption spectrum. The basic principles of photoinduced absorption are explained using the example of electron injection and recombination in dye-sensitized TiO2 in the absence of redox electrolyte.