No abstract

Five novel perylene molecules with different intramolecular charge-transfer (ICT) characters have been synthesized. The relation between the ICT character for different donating groups and the results for their electro- and photochemical properties as well as their performance in nanostructured dye-sensitized solar cells (nDSC) are reported. With the stronger donors, we obtain a shift of the lowest unoccupied molecular orbital (LUMO) to more negative potential versus normal hydrogen electrode (NHE) as well as an increase the charge separation in the dye upon excitation. Ab initio calculations were used to analyze the effects on orbital energies and electron distribution with the different donors. Incorporating the dyes in nDSCs, we see a drastical improvement in the performance for the more polar dyes. In particular, we find a much improved photovoltage because of higher LUMO levels, allowing conduction band tuning in the TiO2 as well as a contribution from the permanent dipoles in the dyes. The photocurrent improves remarkably with increasing ICT character of the dyes. The external quantum efficiency reached over 70%, and the overall solar-to-electrical energy conversion efficiency was improved to almost 4% for the dye with highest ICT character, which can be compared with devices with the standard N719 dye (Ru(dcbpy)2(NCS)2) showing 6% under similar conditions. The performance is a significant improvement compared to previous reports for perylenes and lifts the performance from modest to promising. Initial stability tests show that the dye with the highest performance was spectrally stable after more than 2000 h of irradiation in a solar-cell device.

Two new synthetic approaches to terrylenediimides, highly photostable fluorescent dyes, are described. For the first time terrylenediimide has been synthesised in a straightforward procedure that makes large quantities available. The second route includes an efficient cross-coupling reaction followed by a cyclodehydrogenation. Monofunctionalisation of the imide structure allows terrylenediimides now to be coupled with a variety of compounds, for example, by Suzuki cross-coupling, which can lead to an array of terrylenediimides with new functional groups such as hydroxy, amino, or carboxy groups needed to link up with other molecules. The functionalisation in the bay region is used to tune the properties of terrylenediimides and extend the range of applications, for example, by introducing water solubility. These tetrasubstituted terrylenediimides offer, depending on the substituents used, exciting features such as good solubility in common organic solvents, water solubility, or NIR absorption.

In the red: The synthesis and optical properties of homologous ladder‐type near‐infrared‐absorbing chromophores, namely, two pentarylenebis(dicarboximide)s (green traces; see picture) as well as a hexarylenebis(dicarboximide) (yellow trace) have been studied. A strong bathochromic shift of the absorption maximum is noted with an increasing degree of annulation as is evident from the other traces.

Sunny side up: 1,6‐Dithiophenol‐substituted perylene organic sensitizer 1 was synthesized, and its photovoltaic properties in dye‐sensitized solar cells were assessed. When anchored onto TiO2 film, the dye exhibits an unprecedented incident monochromatic photon‐to‐current conversion efficiency of 87 % and yields a power conversion efficiency of 6.8 % under standard AM 1.5 solar conditions.

Two new one-dimensional organic/inorganic composite polymers were synthesized by the reaction of Cd(NO3)2·4H2O with 1,2-bis(4-pyridyl)ethyne or trans-1,2-bis(4-pyridyl)ethene in several solvent systems. [Cd(NO3)2(1,2-bis(4-pyridyl)ethyne)1.5] n (1), which has an infinite one-dimensional structure with interpenetrating molecular ladders, was obtained by reacting Cd(NO3)2·4H2O with 1,2-bis(4-pyridyl)ethyne in a methylene chloride/methanol solvent system. It crystallized in the monoclinic space group C2/c (No. 15), with a = 20.713(3) Å, b = 17.450(2) Å, c = 14.451(3) Å, β = 129.203(8)°, Z = 8. [Cd(NO3)2(1,2-bis(4-pyridyl)ethene)1.5] n (2) was generated from the reaction of Cd(NO3)2·4H2O with the trans-1,2-bis(4-pyridyl)ethene ligand in an ethanol/water system. It has a novel infinite non-interpenetrating zigzag chain structure which is made up of trans-1,2-bis(4-pyridyl)ethene−Cd−trans-1,2-bis(4-pyridyl)ethene−Cd−trans-1,2-bis(4-pyridyl)ethene building units. Compound 2 crystallized in the triclinic space group P1̄ (No. 2), with a = 10.725(2) Å, b = 10.814(2) Å, c = 9.517(2) Å, α = 104.21(2)°, β = 94.60(1)°, γ = 106.62(1)°, Z = 2. In compound 1, the Cd(II) centers lie in a heptacoordinate environment, while in compound 2, the Cd(II) atoms adopt an octahedral geometry. The two kinds of polymer structures are based on a T-shape and a linear building block, respectively. [Cd(NO3)2(1,2-bis(4-pyridyl)ethane)1.5] n (3) was also synthesized by the reaction of Cd(NO3)2·4H2O with the 1,2-bis(4-pyridyl)ethane ligand in a methylene chloride/methanol system. Polymer 3 forms square units, which are linked through the two Cd(II) centers to give infinite linear chains. The synthesis of compound 3 was reported by Fujita (Fujita, M. J. Chem. Soc., Chem. Commun. 1994, 1977) using a different solvent system.

Novel perylene-3,4,9,10-tetracarboxdiimides (PDI) dyes functionalized with polyphenylene dendrimers attached at the bay region are reported. Derivatives of PDI bearing polyphenylene dendrimers up to the second generation, substituted with an increasing number of triphenylamine (TPA) moieties at the periphery, as well as a related nondendronized model compound were prepared. Intramolecular energy transfer was demonstrated by the observation of PDI emission on excitation of the triphenylamines, and electron transfer was detected by comparing photoluminescence quenching in solvents of different polarity.

Perylene dyes have been widely used as photoreceptors in organic photovoltaics because of their outstanding photo‐, thermal and chemical stability as well as their excellent photophysical properties. Herein we describe a novel generation of perylene dyes based on N‐(2,6‐diisopropylphenyl)‐perylene‐3,4‐dicarboximide. The optical properties of these novel perylenes can be finely tuned via the substituents in the 1‐, 6‐ and 9‐positions of the perylene core. The facile synthesis, tunable orbital and absorption properties, and electrochemical potentials help us to design efficient perylene sensitizers for solar‐cell applications.