Minimizing Energy Losses in Dye‐Sensitized Solar Cells Using Coordination Compounds as Alternative Redox Mediators Coupled with Appropriate Organic Dyes

Abstract

To further boost the efficiency of dye‐sensitized solar cells, a correct evaluation of the real limitations of this type of solar cell should be conducted. From a simple analysis of the photovoltaic data found in the literature, it is evident that the Voc decrease, through energy losses, seems to be the most crucial factor diminishing the overall system efficiency. In particular, losses arising from the regeneration of the dye by the iodide/triiodide redox mediator are huge. The most convenient manner to recuperate these losses is the use of alternative redox mediators with more positive redox potentials than that of the iodide‐based shuttle. Among various types of redox active compounds, ferrocene/ferrocenium, Cu+/2+, and Co2+/3+ complexes are found to be the most effective in solar cells and the obtained efficiencies of more than 12% clearly show that a breakthrough is close, paving revolutionary roads towards making new records.

Light harvesting with Earth abundant d-block metals: Development of sensitizers in dye-sensitized solar cells (DSCs)

“…Compared to the standard dye N719, the ferrocenyl dyes perform well ( [24] provides an excellent overview of cobalt, copper, and ferrocene-based redox mediators, emphasizing means by which energy losses from DSCs can be minimized. In the light of these excellent recent reviews, we will not elaborate further on redox mediators in this article.…”

“…Scheme 1 shows the structures of selected ruthenium-based state-of-the-art dyes used in the currently best performing devices [23,24,25]. Their composition illustrates the key structural features required in a photosensitizer (Figure 4).…”

Push–pull type porphyrin based sensitizers: The effect of donor structure on the light-harvesting ability and photovoltaic performance

“…It is widely recognized that for a fixed redox electrolyte in DSCs, the rise or fall of V oc is determined by the titania electron quasi-Fermi-level (E F,n ), which intrinsically stems from a change of titania conduction band edge (E c ) and/or a variation of titania electron density [15,16]. At a given flux of photocarrier generation, the titania electron density is determined by the interfacial recombination rate of titania electrons with electron accepting species in electrolytes and/or dye cations.…”

Probing the regeneration process of triphenylamine-based organic dyes in dye-sensitized solar cells

“…For a higher open circuit voltage (V oc ), a large number of new redox mediators with more positive redox potential were proposed to replace traditional I À /I 3 -, where the most noticeable are a range of cobalt complexes, whose redox potential can be easily tuned by selecting suitable donor/ acceptor substituents on the ligand and/or modifying the ligand skeleton [24e32]. However, too positive redox potential of the redox mediator would hinder the effective dye regeneration owing to the reduced regeneration driving force [33]. Hence, elucidation of the optimum driving force for dye regeneration is important for the design of DSSCs with maximum efficiency.…”