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A near-IR absorbing dye ( FcS1), in which three fluorene rings were fused with a porphyrazine ring, has been designed and synthesized as a photosensitizer for dye-sensitized solar cells (DSSCs). The fusion of the fluorene rings led to tailoring of the HOMO and LUMO energy levels as well as an expansion of the π-system. The absorption spectrum of FcS1 adsorbed onto a nanocrystalline TiO2 film suggested the formation of J-aggregates with tilted orientation of the macrocyclic ligands. While the power conversion efficiency of DSSCs sensitized with FcS1 was a modest 3.2 % under simulated air mass 1.5 global sunlight, FcS1 can convert the red and near-IR light regions between 600 and 860 nm into electricity. [ABSTRACT FROM AUTHOR]

We designed and synthesized two zinc phthalocyanine sensitizers (PcS27 and PcS28), substituted with branched or cyclic alkoxy chains, to investigate the structural effect of peripheral alkyl chains on the performance of dye-sensitized TiO2 solar cells. The bulky cyclic alkyl chains of PcS28 decreased the adsorption density of PcS28 on the TiO2 electrode, while the terminal branches of alkoxy chains of PcS27 did not influence the adsorption density in comparison to the previously published PcS20 with linear alkoxy chains. Under one sun conditions, PcS27 cells exhibited higher open-circuit voltage but a slightly lower energy conversion efficiency, 6.0% less than PcS20. These results suggest that the small alternation of alkoxy chains resulted in decreasing electron pushing ability of peripheral phenoxy units, giving lower short-circuit current. [ABSTRACT FROM AUTHOR]

Abstract: The lifetime of electrons in the semiconductor electrode of dye-sensitized solar cells (DSSCs) is an important parameter determining the energy conversion efficiency. We propose a method to determine the electron lifetime by stepped current induced measurement of cell voltage in the dark (darkSCIM). Since this technique does not require the creation of photoinduced charges, the lifetime of devices with poorly injecting dyes, or indeed values for devices, which employ no sensitizer, can be determined. [Copyright &y& Elsevier]