Cyanine platelet single crystals: growth, crystal structure and optical spectra.

Crystalline organic semiconducting materials are much in demand for multiple electronic and optoelectronic device applications. Here, solution grown ultrathin rhombic crystals of a trimethine carbocyanine anionic dye are used to establish relationships between structural and optical properties. The dye crystallized in the monoclinic space group P21/c featuring alternating layers of molecules in two different herringbone type patterns, with perchlorate counterions located mostly within one of the two layers. Micro transmittance spectroscopy revealed a broadened spectrum compared to those obtained in solution and in an amorphous thin film. Using polarized light, transmission spectroscopy revealed strong low-energy and weak high-energy bands polarized along the crystallographic b- and c-axis, respectively. Using the extended dipole approximation, significant exciton couplings are predicted between neighboring molecules in the crystal, of the order of the intrinsic monomer reorganization energies associated with nuclear relaxation after excitation, depicting a complex spectral scenario. The exciton coupling pattern explains the relative energies of the b- and c-polarized components but the observed intensities are opposite to expectations based on chromophore alignment within the crystal.

Ternary semitransparent organic solar cells with a laminated top electrode.

Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film.

One-Dimensional Organic-Inorganic Hybrid Perovskite Incorporating Near-Infrared-Absorbing Cyanine Cations.

Hybrid perovskite crystals with organic and inorganic structural components are able to combine desirable properties from both classes of materials. Electronic interactions between the anionic inorganic framework and functional organic cations (such as chromophores or semiconductors) can give rise to unusual photophysical properties. Cyanine dyes are a well known class of cationic organic dyes with high extinction coefficients and tunable absorption maxima all over the visible and near-infrared spectrum. Here we present the synthesis and characterization of an original 1D hybrid perovskite composed of NIR-absorbing cyanine cations and polyanionic lead halide chains. This first demonstration of a cyanine-perovskite hybrid material is paving the way to a new class of compounds with great potential for applications in photonic devices.