title: Interpretation of optoelectronic transient and charge extraction measurements in dye-sensitized solar cells.
abstract: Tools that assess the limitations of dye sensitized solar cells (DSSCs) made with new materials are critical for progress. Measuring the transient electrical signals (voltage or current) after optically perturbing a DSSC is an approach which can give information about electron concentration, transport and recombination. Here we describe the theory and practice of this class of optoelectronic measurements, illustrated with numerous examples. The measurements are interpreted with the multiple trapping continuum model which describes electrons in a semiconductor with an exponential distribution of trapping states. We review standard small perturbation photocurrent and photovoltage transients, and introduce the photovoltage time of flight measurement which allows the simultaneous derivation of both effective diffusion and recombination coefficients. We then consider the utility of large perturbation measurements such as charge extraction and the current interrupt technique for finding the internal charge and voltage within a device. Combining these measurements allows differences between DSSCs to be understood in terms such as electron collection efficiency, semiconductor conduction band edge shifts and recombination kinetics.
authors: Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK. piers.barnes@imperial.ac.uk
authors: Piers R F
authors: PR
authors: Barnes
authors: Kati
authors: K
authors: Miettunen
authors: Xiaoe
authors: X
authors: Li
authors: Assaf Y
authors: AY
authors: Anderson
authors: Takeru
authors: T
authors: Bessho
authors: Michael
authors: M
authors: Gratzel
authors: Brian C
authors: BC
authors: O'Regan