Two novel double‐alkyl functionalized imidazolium ionic liquid crystals have successfully been utilized to demonstrate the benefits of the liquid crystalline phase on the ssDSSC performance. In particular, a good balance between dye regeneration and hole transport is only realized in the liquid crystalline phase. Devices that employ a single component ionic liquid based electrolyte show a remarkably stable efficiency during 1000 h under outdoor operation temperature conditions and 1 sun illumination.

Four novel nanographene/porphyrin hybrids were prepared, characterized, and probed in solar energy conversion schemes. Exfoliation of graphite by means of immobilizing four different porphyrins onto the basal plane of graphene is accompanied by distinct electronic interactions in both the ground and the excited states. In the ground state, a strong loss in oscillator strength goes hand-in-hand with a notable broadening of the porphyrin transitions and, as such, attests to the shift of electron density from the electron donating porphyrins to nanographene. In the excited state, a nearly quantitative quenching of the porphyrin fluorescence is indicative of full charge transfer. The latter is corroborated by femtosecond transient absorption measurements, which reveal the generation of the one-electron oxidized radical cation of the porphyrins with absorption maxima at 490 and 625 nm in the visible region and conduction band electrons in nanographene with features at 890 and 1025 nm in the near infrared region. We have demonstrated the applicability of the new nanographene/porphyrin hybrids in, for example, solar cells. In this regard, the presence of flakes is crucial in terms of influencing the injection processes, preventing aggregation, and reducing recombination losses, which are commonly encountered in porphyrin-based DSSCs.

Different nanocarbons, that is, single-wall carbon nanotubes, graphene, single-wall carbon nanohorns (SWCNHs), and their respective oxidized analogs have been used to fabricate novel doped TiO2 electrodes for DSSCs. Our results indicate that all of the nanocarbons significantly enhance the device characteristics when compared to standard TiO2 electrodes. Overall, our most outstanding finding is that SWCNH derivatives are also a plausible material for developing highly-efficient DSSCs.

No abstract

In the current work, we have explored a novel synthetic route towards metalated porphycenes and their use in p-type NiO-based dye-sensitized solar cells. Particular emphasis is placed on the influence that the relative positioning of the anchoring group exerts on the DSSC performance.Factors that favor dye-sensitized solar cells (DSSCs) as a key technology in solar-energy conversion schemes include low purity requirements and easy accessibility, low costs, fast processing, and simple up-scaling. DSSCs have been rendered even more attractive by recent progress in solid-state and flexible devices. 1,2 To date, record efficiencies as high as 13% have been reported for n-type DSSCs. 3 However, efficient p-type DSSCs, which complement n-type DSSCs in, for example, tandem configurations, are necessary for obtaining values beyond 13%, and are therefore the subject of intensive investigation. 4 Regardless of whether the semiconductor materials are n-or p-type, the chromophore attached to the semiconductor electrode is decisive in terms of light harvesting, charge transfer, and charge transport. Diverse organic or inorganic chromophores have recently been tested in both types of DSSCs. [5][6][7][8] Fine tuning synthetic parameters such as the metalation of the chromophore, the nature of the anchor, and the bridge that links the chromophore to the anchor, have made control over important characteristics like highly effective charge separation, reduced charge recombination, and long term stability possible. [9][10][11][12] Semiconductor nickel oxide (NiO) stands out as an electrode material for p-type DSSCs. 7,[13][14][15] This has triggered the design of novel light-harvesting and electron-accepting chromophores. 13 We have focused on porphycenes because of their similarity to porphyrins and phthalocyanines. 16,17 In contrast to the electrondonating features of porphyrins and phthalocyanines, which are widely used in n-type DSSCs, 8,18 porphycenes are strong electron acceptors, making them more suitable building blocks for p-type DSSCs. Only a few examples of the use of free-base porphycenes in solar energy devices are known to date. 19,20 We now report two major achievements. The first is the development of a new synthetic route to nickel porphycenes, which have barely been investigated previously. We have characterized the novel nickel porphycenes by physicochemical and computational techniques. Secondly, we have used these nickel porphycenes in p-type NiO-based DSSCs. We have been able to rationalize the overall performances in terms of the position and the nature of the anchor groups and, in turn, to establish new guidelines to designing novel electron acceptors.Three different nickel porphycenes were prepared -Scheme 1 -see ESI. † To obtain the target porphycenes, the 2,7,12,17-tetra-npropylporphycenato nickel (1) was chosen as starting material. Firstly, the peripheral alkyl chains ensure solubility in a wide variety of solvents. Secondly, the established chemistry of 1 allows the target featuring a vinyl group as a...