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 (Rr) while that at the substrate/electrolyte interface corresponds to a shunt resistance (Rsh). 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 Rs 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.