The High Aqueous Solubility of K 2 S and Its Effect on Bulk and Photoelectrochemical Characteristics of Cd ( SeTe ) / S x = Cells: II . Variation of Sulfur/Sulfide Ratio

Abstract

Variation of sulfur/alkali sulfide ratio is shown to modify significantly transparency, redox potential, and half‐life of aqueous polysulfide solutions. In electrolytes containing 3m total sulfur and various concentration of , shift in from 2.5 to 0.4 is calculated to change the primary polysulfide species from to in solution. When these electrolytes are employed in photoelectrochemical solar cells, a decrease in , from 2.5 to 1.8, increases relative optical to electrical conversion efficiencies by 50%, due primarily to improvement in fill factor, paralleled by an increase in . At , photovoltage, photocurrent, and fill factor are depressed. Photovoltage decrease is attributed to negative shifts in redox potential not paralleled by commensurate shifts in flatband potential. At low , an observed decrease in fill factor and photocurrent are related to a decrease in in solution and to ion pairing.