Conventional squaraine dyes exhibit an intense absorption band in the red region of the solar spectrum and with appropriate design can also have high energy absorption as well, making them interesting building blocks toward achieving panchromatic dyes for dye sensitized solar cell (DSSC) applications. In this report, eight squaraine dyes with thiophene, 4-hexyl-4H-dithieno­[3,2-b:2′,3′-d]­pyrrole, dithieno­[3,2-b:2′,3′-d]­thiophene, and 4,4-bis­(2-ethylhexyl)-4H-silolo­[3,2-b:4,5-b′]­dithiophene (DTS) π-bridges with cyanoacetic acid (CA) and cyanophosphonic acid (PA) acceptor/anchoring groups are synthesized to extend the squaraine absorption into the 450–550 nm region and to provide different spatial arrangements of solubilizing groups. Squaraines with CA anchoring groups have higher power conversion efficiencies compared to their PA analogs, with the highest being 8.9% for the DTS-based dye, which is among the highest reported in the literature for squaraine dyes. This is due to high short circuit currents (J SC) and increased open circuit voltages (V OC). Dyes with PA anchoring groups exhibited lower J SC resulting from decreased charge injection efficiency, as determined by femtosecond transient absorption spectroscopy. This study suggests that out-of-plane bulky substituents may increase DSSC performance not only by increasing J SC through decreased aggregation but also by increasing V OC through decreased TiO2/electrolyte recombination.

Maintaining high incident light absorption while minimizing luminescence reabsorption is a key challenge for organic luminescent solar concentrators (LSCs). Energy migration and trapping using light-harvesting donors and a low-energy highly emitting acceptor is one strategy to reduce the reabsorption issue. However, concentration quenching and the potential formation of quenching aggregates is a limiting factor in realizing efficient devices. We describe the synthesis of a novel molecularly insulated perylene diimide that can resist luminescence quenching at concentrations in excess of 50 mM. Photophysical measurements show the insulated perylene diimide has an excitation energy migration diffusion length of 230 ± 10 Å at 60 mM in poly(methyl methacrylate). LSC devices using a mixture of the insulated perylene diimide light absorber and perylene red (LR305) as the low-energy trap emitter exhibit reduced reabsorption and a better current output than LR305 only devices. The results demonstrate that appropriately designed organic molecule dyes can potentially meet the stringent requirements required for efficient LSCs. S tationary light concentration without external cooling can be realized using luminescent solar concentrators (LSCs), making these devices attractive for building integrated photovoltaic devices. A typical LSC consists of large sheets of plastic or glass containing luminescent molecules that absorb the solar spectrum and then re-emit the absorbed energy into a waveguide mode that directs the luminescence to the thin edges of the concentrator. Edge-mounted solar cells can then harvest the concentrated luminescence for photoelectric conversion. Reabsorption of the emitted light in the waveguide limits the achievable light concentration contributing to parasitic losses such as re-emission into the escape cone or nonunity fluorescence quantum efficiency due to competing nonradiative processes. Separation of both the energy of the peak maxima of absorption and emission (the Stokes shift) and tail absorption of the chromophores in an LSC is crucial in reducing reabsorption. 1,2 Organic solar concentrators that use diluted organic chromophores in inert host matrices are lagging behind their inorganic counterparts due to their small Stokes shifts. 3 A key advantage of organic chromophores over inorganic materials is their solubility in inexpensive host matrices or waveguides, such as poly(methyl methacrylate) (PMMA) or glass, without any complicated processing and the ability to fine-tune their properties by simple molecular engineering approaches. This is particularly important for thin-film LSCs where the concentration required to achieve total light absorption over the wavelength range of the chromophore can be high ( Figure 1).Modification of dyes to achieve a large Stokes shift has achieved only limited success for LSC applications. In some cases, increasing the Stokes shift of the dye has led to a decreased quantum yield and there often remains the long tail absorption of the dye. 4 Energy transfer ...

Development of single-molecule localization microscopy (SMLM) has sparked a revolution in biological imaging, allowing "superresolution" fluorescence microscopy below the diffraction limit of light. The past decade has seen an explosion in not only optical hardware for SMLM but also the development or repurposing of fluorescent proteins and small-molecule fluorescent probes for this technique. In this review, written by chemists for chemists, we detail the history of single-molecule localization microscopy and collate the collection of probes with demonstrated utility in SMLM. We hope it will serve as a primer for probe choice in localization microscopy as well as an inspiration for the development of new fluorophores that enable imaging of biological samples with exquisite detail.

Panchromatic dyes with absorption profiles extending into the near infra-red are of interest to researchers in the field of dye sensitized solar cells (DSSCs), as they offer potential access to a wide energy range of photons necessary to enhance solar to electric power conversion efficiencies (PCEs). In this report, a porphyrin with a Soret band absorbing at high energy is combined with a squaraine absorbing at low energy via an acetylene linker to form a bichromophoric sensitizer with molar extinctions on the order of 10 5 M -1 cm -1 and an incident photon-to-current efficiency (IPCE) onset of ~850 nm. Various bulky substituents were installed on both the porphyrin and squaraine moieties, and conjugation was increased with π-bridge spacers to achieve a PCE of 7.6%, which is up to 15% higher than a comparable squaraine-only dye. For the most part, charge injection dynamics indicate slower charge injection rates and lower injection quantum yields for these bichromophoric sensitizers compared to non-porphyrin squaraine-based DSSC sensitizers. Nevertheless, higher PCE was observed for most porphyrincontaining dyes due largely to increased panchromaticity.

Nine 1,3,6,8-tetraarylpyrenes were prepared and characterized for OLED-based blue-light emission.

Chemisorption of an organic monolayer to tune the surface properties of a transparent conductive oxide (TCO) electrode can improve the performance of organic electronic devices that rely on efficient charge transfer between an organic active layer and a TCO contact. Here a series of perylene diimides (PDIs) was synthesized and used to study relationships between monolayer structure/properties and electron transfer kinetics at PDI-modified indium tin oxide (ITO) electrodes. In these PDI molecules, one of the imide substituents is a benzene ring bearing a phosphonic acid (PA) and the other is a bulky aryl group that is twisted out of the plane of the PDI core. The size of the bulky aryl group and the substitution of the benzene ring bearing the PA were both varied which altered the extent of aggregation when these molecules were absorbed as monolayer films (MLs) on ITO, as revealed by both attenuated total reflectance (ATR) and total internal reflection fluorescence (TIRF) spectra. Polarized ATR measurements indicate that in these MLs, the long axis of the PDI core is tilted at an angle of 33˚-42˚ relative to the surface normal; the tilt angle increased as the degree of bulky substitution increased. Rate constants for electron transfer (k s,opt ) between these redox-active modifiers and ITO were determined by potential-modulated ATR spectroscopy. As the degree of PDI aggregation was reduced, k s,opt declined which is attributed to a reduction in the lateral electron self-exchange rate between adsorbed PDI molecules, as well as the heterogeneous conductivity of the ITO electrode surface. Photoelectrochemical measurements using a dissolved aluminum phthalocyanine as an electron donor showed that ITO modified with any of these PDIs is a more effective electron-collecting electrode than bare ITO.

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The morphological and electrical properties of 2,11-di-tert-butyl-6,7,15,16-tetrakis(hexylthio)quinoxalino[2′,3′: 9,10]phenanthro[4,5-abc]phenazine (TQPP) organic molecule combined with butylamine (BAM)-modified graphene sheets (GSs) are described. The grafting of the amine onto the graphene sheet plane promotes its compatibility with this BAM soluble molecule, leading to the preparation of homogeneous films containing exfoliated graphene sheets, as demonstrated by infrared spectroscopy, field emission electron microscopy, and Raman spectroscopy. The film deposited from the BAM-modified GSs/TQPP blend showed a photoelectrical response higher than those prepared with neat molecule and GSs/TQPP blend, respectively.