The Redox Pair Chemical Environment Influence on the Recombination Loss in Dye-Sensitized Solar Cells

Abstract

Reduction of recombination losses in dye-sensitized solar cells (DSC) is vital to fabricate efficient devices. The electron recombination lifetime depends on the relative energetics of the semiconductor and the redox pair and on the chemical nature of the electrolyte (hole conductor). In this work, the behavior of the electron lifetime in DSC devices prepared with various solvents (acetonitrile, valeronitrile, ethylene carbonate, pure ionic liquids), additives (lithium ions, TBP), and redox pairs (iodide/iodine, Co(II)/Co(III)) is thoroughly studied using high-extinction dyes. Lifetimes were extracted by means of small-perturbation electrochemical techniques (impedance spectroscopy, intensity-modulated photovoltage spectroscopy) and open-circuit voltage decays. To ensure a safe inner comparison and a proper interpretation, all devices were constructed using the same type of TiO2 electrode and the same dyes (C101 and Z907 for iodide/iodine and cobalt-based electrolytes, respectively). Furthermore, small-pe...