Characterization of N,N′-dimethyl-3,4,9,10- perylenetetracarboxylic acid diimide and phthalocyaninatozinc(ii) in electrochemical photovoltaic cells

Abstract

As a direct comparison to all-solid state photovoltaic cells, photoelectrochemical cells consisting of n-type N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (MePTCDI) and p-type phthalocyaninatozinc(ii) (PcZn) thin film electrodes vapour-deposited onto ITO have been investigated in aqueous ferri/ferrocyanide, p-benzoquinone/hydroquinone or I3−/I− electrolytes. The ferri/ferrocyanide cell has been studied in more detail, and the results are discussed with regard to the HOMO-, LUMO- and Fermi-energies of the materials used. A setup of the electrodes in a tandem cell could increase the efficiency of the cell due to improved light harvesting. Saturation of the photocurrent with increasing ferri/ferrocyanide electrolyte concentration at single PcZn or MePTCDI electrodes is discussed using a model of reactant adsorption prior to the charge transfer step. In addition, a decrease observed for the open-circuit voltage of the entire cell with increasing ferri/ferrocyanide concentration leads to an optimum concentration of 10−3 moldm−3.