CATION EFFECT ON THE CDSE-LIQUID JUNCTION

The effect of cation on the CdSe/polysulfide photoelectrochemical (PEC ) solar cell has been investigated. The current-potential response of the polysulfide electrolyte on a platinum electrode was measured as a function of the alkali metal cation in solution. There was a -33 m V s hift in the redox potential and an increase in the current when the ca tion changed from Na+ to Cs+. The performance of the CdSe/polysulfide PEC cell with both polycrystalline and single-crystal semiconductor el ectrodes increased in the open-circuit potential, the short-circuit cu rrent, the fill factor, and the energy conversion efficiency when Cs p olysulfide was used with K or Na polysulfide. Impedance measurements w ere made on the electrodes in polysulfide solutions with the different cations. The results for both electrolytes showed a negative shift in the flatband potential, an increase in the apparent charge-carrier co ncentration, and an increase in the frequency dispersion of the measur ements with the addition of Cs+. The impedance measurements also showe d a dependence on the orientation of the CdSe crystal. The effects abo ve are related to a combination of a change in the solution and the su rface of the semiconductor. The stoichiometric distribution of the pol ysulfide species changes with the addition of Cs+ and the surface of t he semiconductor changes, facilitating charge transfer across the semi conductor/electrolyte interface.