Synthesis of Perylene-3,4-mono(dicarboximide)−Fullerene C60 Dyads as New Light-Harvesting Systems

Phenylene-Bridged Perylene Monoimides as Acceptors for Organic Solar Cells: A Study on the Structure-Property Relationship

A series of non-fullerene acceptors based on perylene monoimides coupled in the peri position through phenylene linkers were synthesized via Suzuki-coupling reactions. Various substitution patterns were investigated using density functional theory (DFT) calculations in combination with experimental data to elucidate the geometry and their optical and electrochemical properties. Further investigations of the bulk properties with grazing incidence wide angle X-ray scattering (GIWAXS) gave insight into the stacking behavior of the acceptor thin films. Electrochemical and morphological properties correlate with the photovoltaic performance of devices with the polymeric donor PBDB-T and a maximum efficiency of 3.17 % was reached. The study gives detailed information about structure-property relationships of perylene-linker-perylene compounds.

Visible-Light-Mediated Synthesis of AzaBenzannulated Perylenediimide-Based Light-Harvesting Dyads

Intramolecular imine photocyclization has been explored for grafting on the bay region of perylenediimide (PDI) different electro- and photoactive chromophores to achieve new AzaBenzannulated-PDI (AzaBPDI) dyads. Triphenylamine (TPA), fluorene (Fl), perylenemonoimide (PMI), and perylenediimide (PDI) units have been successfully assembled to AzaBPDI using this straightforward one-pot synthesis starting from the easily accessible 1-aminoPDI. This original procedure was compared to the well-known Pictet-Spengler reaction and appears to be an attractive alternative in terms of versatility and efficiency with higher yields obtained. The optical and electrochemical properties of these molecular systems demonstrated large absorption capabilities in the visible range, good accepting abilities with low LUMO levels, and efficient electronic interactions between chromophoric units such as energy or electron transfers. In addition, with their large dihedral angle estimated by theoretical calculations, those dyads should present interesting applications in various organic optoelectronic devices. In particular, the PMI-AzaBPDI and PDI-AzaBPDI dyads presenting low LUMO levels, a broad absorption in the visible range, and a twisted conformation make them good candidates as non-fullerene acceptors in organic solar cells.

The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents

C60 fullerene exhibits unique optical properties that have high potential for wide photo-optical applications. To analyze the optical properties of C60, its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, non-polar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to Ag → T1u and Ag → T1g transitions. However, these bands differed from the solid C60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C60 and the organic solvents due to their different solvent polarities.

Photophysics of perylene monoimide-labelled organocatalysts

A fluorophore-tagged organocatalyst undergoes electron transfer in polar solvents allowing to sense the presence of its free quinuclidine catalytic site.

Artificial miniaturized luminescent materials based on perylene-covered glass surfaces

Cu(i)-Catalyzed 1,3-dipolar cycloaddition was used to construct a luminescent monolayer for an ICT-showing pyrrolidino-perylene association (5PMI) on glass surfaces, which represents a rare perylene chromophore, to date, anchored to a solid surface.

Synthesis and Properties of Axially Symmetrical Rigid Visible Light-Harvesting Systems Containing [60]Fullerene and Perylenebisimide

Two visible light-harvesting perylenebisimide (PDI)-[60]fullerene (C₆₀) systems, dyad P1 with one C₆₀ unit and triad P2 with two C₆₀ units, have been synthesized. Both systems are axially symmetrical with a rigid biphenyl linker, ensuring a relatively fixed spatial distance between the donor and acceptor, preventing through-space interaction, and enhancing energy transfer. Steady-state and transient spectroscopy, electrochemistry, as well as theoretical calculations have been used to investigate the electrochemical and photophysical properties of the two systems. Steady-state and time-resolved spectroscopy demonstrate that the excited state is featured by an efficient intramolecular energy transfer from PDI to C₆₀. Then, the high efficient intrinsic intersystem crossing of C₆₀ eventually leads to the production of the triplet C₆₀. The extensive visible light absorption of PDI in the range of 400-650 nm and the final localization of the excited energy at the triplet C₆₀ make these compounds ideal singlet oxygen inducers. Further investigation shows that the photooxidation capability for both compounds is significantly enhanced with respect to either PDI or C₆₀ and even better than that of the commonly used triplet photosensitizer methylene blue (MB). The double C₆₀ moieties in P2 display a better result, and the photooxidation efficiency of P2 increases 1.3- and 1.4-fold compared to that of P1 and MB, respectively. The combination of a light-harvesting unit with an intersystem crossing unit results in a highly efficient photooxidation system, which opens up a new way to triplet photosensitizer design.

Flat-on ambipolar triphenylamine/C60 nano-stacks formed from the self-organization of a pyramid-sphere-shaped amphiphile

The study identified the flat-on dual-channel nano-structure and the ambipolar characteristics of a novel giant pyramid-sphere shape amphiphile.

A giant amphiphile, which is constructed with an amorphous nano-pyramid (triphenylamine, TPA) and a crystalline nano-sphere (C₆₀), was synthesized. Structural characterization indicates that this pyramid-sphere-shaped amphiphile (TPA–C₆₀) forms a solvent-induced ordered phase, in which the two constituent units self-assemble into alternating stacks of two-dimensional (2D) TPA and C₆₀ nano-sheets. Due to the complexity of the molecular structure and the amorphous nature of the nano-pyramid, phase formation was driven by intermolecular C₆₀–C₆₀ interactions and the ordered phase could not be reformed from the TPA–C₆₀ melt. Oriented crystal arrays of TPA–C₆₀, which contain flat-on TPA/C₆₀ nano-stacks, can be obtained via a PDMS-assisted crystallization (PAC) technique. The flat-on dual-channel supramolecular structure of TPA–C₆₀ delivered ambipolar and balanced charge-transport characteristics with an average μ_e of 2.11 × 10^–4 cm² V^–1 s^–1 and μ_h of 3.37 × 10^–4 cm² V^–1 s^–1. The anisotropic charge-transport ability of the pyramid-sphere-shaped amphiphile was further understood based on the lattice structure and the lattice orientation of TPA–C₆₀ revealed from electron diffraction analyses.

Rapid microwave-assisted synthesis of N-benzyl fulleropyrrolidines under solvent free conditions

Rapid microwave-assisted synthesis of N-benzyl fulleropyrrolidines under solvent free conditions.

Fulleropyrrolidine molecular dumbbells act as multi-electron-acceptor triads. Spectroscopic, electrochemical, computational and morphological characterizations

Three novel fulleropyrrolidine dumbbells consisting three electron acceptor moieties joined by alkyl linker displaying tunable electrical and morphological properties were synthesized and characterized.

A double-acceptor as a superior organic dye design for p-type DSSCs: high photocurrents and the observed light soaking effect

Herein, we report three novel single donor double acceptor dyes, BH2, 4, and 6, for use in p-type dye sensitized solar cells (DSSCs). BH4 yields one of the highest photocurrents, 7.4 mA cm(-2), to date. The high performance is achieved via a shorter synthetic route and no exotic materials or cell-building techniques. We suggest a structural principle when building dyes whereby one adopts a double acceptor/single anchor when a triphenylamine moiety is incorporated into a dye for p-type DSSCs. This strategy increases the molar extinction coefficient while simultaneously reducing the number of synthetic steps. The molar extinction coefficients (99 980 M(-1) cm(-1)) reported herein are among the highest reported. Finally, we report the first-ever-observed light soaking effect in p-type DSSCs.

Energy-funneling-based broadband visible-light-absorbing bodipy-C60 triads and tetrads as dual functional heavy-atom-free organic triplet photosensitizers for photocatalytic organic reactions

C60-bodipy triads and tetrads based on the energy-funneling effect that show broadband absorption in the visible region have been prepared as novel triplet photosensitizers. The new photosensitizers contain two or three different light-harvesting antennae associated with different absorption wavelengths, resulting in a broad absorption band (450-650 nm). The panchromatic excitation energy harvested by the bodipy moieties is funneled into a spin converter (C60), thus ensuring intersystem crossing and population of the triplet state. Nanosecond time-resolved transient absorption and spin density analysis indicated that the T1 state is localized on either C60 or the antennae, depending on the T1 energy levels of the two entities. The antenna-localized T1 state shows a longer lifetime (τ(T)=132.9 μs) than the C60-localized T1 state (ca. 27.4 μs). We found that the C60 triads and tetrads can be used as dual functional photocatalysts, that is, singlet oxygen ((1)O2) and superoxide radical anion (O2(.-)) photosensitizers. In the photooxidation of naphthol to juglone, the (1)O2 photosensitizing ability of the C60 triad is a factor of 8.9 greater than the conventional triplet photosensitizers tetraphenylporphyrin and methylene blue. The C60 dyads and triads were also used as photocatalysts for O2(.-)-mediated aerobic oxidation of aromatic boronic acids to produce phenols. The reaction times were greatly reduced compared with when [Ru(bpy)3Cl2] was used as photocatalyst. Our study of triplet photosensitizers has shown that broadband absorption in the visible spectral region and long-lived triplet excited states can be useful for the design of new heavy-atom-free organic triplet photosensitizers and for the application of these triplet photosensitizers in photo-organocatalysis.

Styryl Bodipy-C60 dyads as efficient heavy-atom-free organic triplet photosensitizers

C60-styryl Bodipy dyads that show strong absorption of visible light (ε = 64,600 M(-1) cm(-1) at 657 nm) and a long-lived triplet excited state (τT = 123.2 μs) are prepared. The dyads were used as heavy-atom-free organic triplet photosensitizers for photooxidation of 1,5-dihydroxynaphthalene via the photosensitizing of singlet oxygen ((1)O2). The photooxidation efficiency of the dyads compared to the conventional Ir(III) complex (1)O2 photosensitizer increased 19-fold.

Electric field dependent photocurrent generation in a thin-film organic photovoltaic device with a [70]fullerene-benzodifuranone dyad

A [70]fullerene-benzodifuranone acceptor dyad synthesized by a Ag⁺-mediated coupling reaction was used to construct a thin-film organic solar cell. The fullerene and the benzodifuranone dye in the dyad have close-lying LUMO levels in the range of 3.7-3.9 eV, so that energy transfer from the dye to the fullerene can take place. A p-n heterojunction photovoltaic device consisting of a tetrabenzoporphyrin and a [70]fullerene-benzodifuranone dyad showed a weak but discernible contribution from light absorption of the dyad to the photocurrent under both a positive and a negative effective bias. These results indicate that the benzodifuranone moiety attached to the acceptor contributes to light-harvesting by energy transfer.