Role of temperature in the recombination reaction on dye-sensitized solar cells

Abstract

The performance of photovoltaic (PV) devices as a function of temperature is crucial for technicaldevelopment and for accurate commercial information. Along with solar irradiance, temperature is themost important operating factor of the PV device performance. Normally, it is widely accepted that dyesensitized solar cells (DSC) show minimal energy efficiency dependence with temperature (20-60 1C).The energy efficiency in DSCs depends on the light absorption, charge transport (ohmic resistances)and recombination rates. In this study, the recombination reaction kinetics was studied within a widetemperature range. A unique laser assisted sealing technique that allows studying the temperature effectbetween 5 1C and 105 1C without electrolyte leakage or external contamination was used. To the bestof our knowledge, this is the highest operating temperature ever considered in kinetic studies of liquidstate DSCs. The electrochemical reaction between electrons and triiodide/iodide ions was shown to bethe most important factor for determining the energy efficiency of DSCs as a function of temperature. Itwas concluded that the activation energy of the recombination reactions depends on the interfacewhere it happens - TiO2/electrolyte and SnO2-F/electrolyte - and on the temperature. It was found thatin addition to temperature having a deep influence on the recombination reaction rate, the energy of theinjecting electron is also critical. These conclusions should provide solid ground for further developments inthe DSCs and perovskite solar cells, and allow a better comparison of the energy efficiency of different PVtechnologies over a range of operating temperatures.