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

The performance of photovoltaic (PV) devices as a function of temperature is crucial for technical development and for accurate commercial information. Along with solar irradiance, temperature is the most important operating factor of the PV device performance. Normally, it is widely accepted that dye sensitized solar cells (DSC) show minimal energy efficiency dependence with temperature (20-60 °C). 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 wide temperature range. A unique laser assisted sealing technique that allows studying the temperature effect between -5 °C and 105 °C without electrolyte leakage or external contamination was used. To the best of our knowledge, this is the highest operating temperature ever considered in kinetic studies of liquid state DSCs. The electrochemical reaction between electrons and triiodide/iodide ions was shown to be the most important factor for determining the energy efficiency of DSCs as a function of temperature. It was concluded that the activation energy of the recombination reactions depends on the interface where it happens - TiO2/electrolyte and SnO2-F/electrolyte - and on the temperature. It was found that in addition to temperature having a deep influence on the recombination reaction rate, the energy of the injecting electron is also critical. These conclusions should provide solid ground for further developments in the DSCs and perovskite solar cells, and allow a better comparison of the energy efficiency of different PV technologies over a range of operating temperatures.