Cation Effects in p-Type Dye Sensitized Solar Cells

The performance of dye sensitized solar cells (DSSCs) depends on the properties and interactions of three fundamental components: the semiconductor, chromophore, and electrolyte. For the electrolyte, the dependence of DSSC performance on the identity and valence state of the spectator cation has not been well studied in p-type semiconductor systems, although the effects of these species in n-type TiO2 devices are significant, producing large shifts in semiconductor flat band potential, charge transfer kinetics, photocurrent, and open-circuit voltage (VOC). Here, we vary the spectator cation in p-type NiO DSSCs and demonstrate an increase in VOC by over 50% with two common redox couples. Using optimal cations, high VOC values are achieved without a significant reduction in photocurrent. Mott-Schottky analysis and electrochemical impedance spectroscopy reveal that the cation can shift the flat-band potential of NiO by nearly 1 V and substantially alter the lifetime of charge carriers and charge transfer res...