Iodine-free redox couples for dye-sensitized solar cells

Abstract

Redox couples, as one of the crucial components of dye-sensitized solar cells, have been investigated for many years. Due to the many drawbacks of I⁻/I₃⁻ electrolyte, scientists have paid more attention to seeking other alternative electrolyte systems. Up to now, the best efficiency of iodine-free redox couple-based DSCs, 7.5%, has been achieved by ferrocene/ferrocenium redox couple under AM 1.5G, 100 mW cm⁻² light illumination and other redox couples also show the promising future in DSCs. In this feature article, we systematically present three series of iodine-free redox couples including metal-complexes, inorganic and pure organic redox couples, and further compare the different photovoltaic and photophysical properties of these redox couples. As a consequence, the goals of this article are to show the important progress achieved in the redox couples research area of DSCs and analyze the advantages as well as the disadvantages of these redox couples to speed up the further development of iodine-free redox couples in the future.