Calculating current density-voltage curves of dye-sensitized solar cells: A straight-forward approach

Abstract

An analytical expression of current density-voltage (j-V) relation in dye-sensitized solar cells (DSSCs) has been derived from a modified diode model, which is a simplified form of the standard equivalent circuit model of DSSCs. The model has two resistors in parallel that resist the loss of photocurrent and a series resistor (Rs) across which drop of photovoltage occurs. The current loss due to back reaction at the TiO2/electrolyte interface is related to a recombination resistance (R-r) while that at the substrate/electrolyte interface corresponds to a shunt resistance (R-sh). Even though the final j-V expression for complete DSSCs is an implicit equation, calculation of the j-V expression for photoelectrodes of DSSCs followed by potential correction due to R-S facilitates the calculation of j-V curve of complete cell even on a spread sheet without any complex algorithm. Moreover, the paper discusses how the model parameters can be extracted from a systematic analysis of electrochemical impedance spectroscopy (EIS) data together with j-V curve of DSSCs. The model can successfully reproduce experimental j-V curves and show the effect of different model parameters. Thus, it is a powerful tool to find out the key factors that limit the performance of DSSCs. (c) 2013 Elsevier B.V. All rights reserved.