A
facile and low-cost strategy to improve stability and conversion efficiency of
CdSe film electrodes prepared by chemical bath deposition (CBD) onto FTO/glass
substrates, is described. The naked CdSe film electrodes, with band gap value 1.8
eV, photo-corroded under the photoelectrochemical
(PEC) working conditions and exhibited no photocurrent. The CdSe film peeled
out in short times. Attempts
made to enhance stability and efficiency of naked CdSe electrodes, by chemical
etching or pre-scratching the FTO surface with fine sand-paper, failed to
improve film PEC characteristics. Annealing the glass/FTO/CdSe film also
failed to improve its PEC stability or efficiency. When coated with the electro-active species Tetra(-4-pyridyl)porphyrinatomanganeseIII/II
sulfate embedded inside polysiloxane films (MnPyP/Polysil) the CdSe films did
not peel out under the PEC conditions. The coated electrode (glass/FTO/CdSe/MnPyP/Polysil)
clearly exhibited photocurrents.
Pre-annealing the naked CdSe
film at 350oC, followed by coating with MnPyP/Polysil further enhanced the electrode PEC
characteristics. Additional heating of the prepared glass/FTO/CdSe/MnPyP/Polysil
electrode at 120oC also enhanced its PEC characteristics. The mode of action of the MnPyP/Polysil
coating has been attributed to its ability to behave as a charge transfer
catalyst at the solid/liquid interface. The new technique described here could
also be potentially valuable for
other types of thin film electrode materials.