Recombination between injected electrons and iodine limits the photovoltage in dye-sensitized solar cells (DSSCs). We have recently suggested that many new dye molecules, intended to improve DSSCs, can accelerate this reaction, negating the expected improvement (J. Am. Chem. Soc. 2008, 130, 2907). Here we study two dyes with only a two-atom change in the structure, yet which give different V(oc)s. Using a range of measurements we show conclusively that the change in V(oc) is due solely to the increase in the recombination rate. From the structure of the dyes, and literature values for iodine binding of similar compounds, we find that it is very likely that the change in V(oc) is due solely to the difference in iodine binding at the site of the two-atom change. Using the large amount of literature on iodine complexation, we suggest structures for dyes that might show improved V(oc).
Stable and efficient dye‐sensitized solar cells based on water‐containing electrolytes are shown. For water contents up to 40%, no decrease in efficiency is seen. The cells are demonstrated to be stable for long periods of continuous illumination.This work lays a foundation for the further development of water‐based cells for commercial production.
Photocurrents generated by thick, strongly absorbing, dye-sensitized cells were reduced when the electrolyte iodine concentration was increased. Electron diffusion lengths measured using common transient techniques (L(n)) were at least two times higher than diffusion lengths measured at steady state (L(IPCE)). Charge collection efficiency calculated using L(n) seriously overpredicted photocurrent, while L(IPCE) correctly predicted photocurrent. This has implications for optimizing cell design.
Paired electron transfers (ET) induced by the absorption of two photons by synthetic dendrimers are observed in first-, second-, and third-generation dendrimers comprised of a viologen-like core and an array of naphthalene peripheral groups. Flash photolysis and transient absorption techniques show that the yield of photoinduced double ET depends on laser intensity in the two largest dendrimers, NBV2(+2) and NBV3(+2). Their photochemical behavior thus requires an unusual multiphoton kinetic scheme. These dendrimers constitute the first synthetic models capable of multiple electron redox events deriving from a defined molecular architecture, thus mimicking natural light-collecting antenna systems.
Yes. Testing 7 different metals as a substrate for a counter electrode in dye sensitized solar cells (DSSC) showed that some metals can be a good option for use with cobalt electrolyte. It was found that Stainless steels 304 and 321 as well as Ni and Ti suit well to the counter electrodes in DSSCs with cobalt electrolyte. In these 4 cases both the efficiency and the lifetime were similar to the reference cells on conducting glass substrates. In contrast, the cells with Al, Cu and Zn substrates suffered from both a low efficiency and a poor stability. These three metals had clear marks of corrosion such as apparent corrosion products in the aged cells. Additionally, we also investigated how the different types of catalyst materials perform in the case of a metal counter electrode (stainless steel 304) with cobalt electrolyte in comparison to reference glass cells. Among the 5 different catalyst layers the best results for stainless steel electrode were achieved with low temperature platinization whereas polymer catalysts poly(3,4-ethylenedioxythiophene)-p-toluenesulfone and poly(3,4-ethylenedioxythiophene)-polystyrenesulfone that worked well on the glass worked very poorly on the metal.
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