Structure-activity relationship for the solid state emission of a new family of "push-pull" pi-extended chromophores

We report the design, synthesis, molecular optical properties, and solid state emissive behaviour of a series of novel compounds, which, similar to the archetypal AIE luminogen tetraphenylethene, are formed of a central olefin stator and decorated with either three or four rotors. These rotors, being either electron-rich substituted benzenes, or electron-withdrawing functional groups (esters, ketones, cyano groups) confer a "push–pull" character to the overall molecular structure. Building on both new and already published contributions, a comprehensive picture of the properties and the potential of these compounds is provided

Nematicon-driven injection of amplified spontaneous emission into an optical fiber

We investigate experimentally the interaction between amplified spontaneous emission (ASE) and a soliton, which are both generated in a dye-doped nematic liquid crystal (LC) cell. A light beam is injected through an optical fiber slid into the cell to form a soliton beam. ASE is then automatically collected by this self-induced waveguide and efficiently coupled into the same optical fiber, in the backward direction. We demonstrate that the presence of the soliton improves the ASE collection by one order of magnitude. We also show that the ASE is highly polarized in the plane of the LC cell and that the ASE spectrum depends on the pump stripe orientation with respect to the LC director. The origin of the spectral anisotropy of the gain curves is determined with the help of femtosecond pump-probe spectroscopy.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A comparative study of low-cost coating processes for green & sustainable organic solar cell active layer manufacturing

Owing to their facile integration into existing commercial products, high volume manufacturing of organic solar cells (OSCs) can be expected in the upcoming years. Therefore, it is important to evaluate the performance and sustainability of various active layer coating methods for OSCs. Herein, we compare four active layer coating processes: spin-coating, blade-coating, spray-coating and push-coating for poly(2,7-carbazole-alt-dithienylbenzothiadiazole):[6,6]-Phenyl-C71-butyric acid methyl ester (PCDTBT:PC71BM) active layers deposition. The optical, morphological and photovoltaic parameters of the active layers are studied. The suitability of each coating method for industrial manufacturing of PCDTBT:PC71BM OSCs is discussed in terms of environmental impact, necessary investments and running costs. Our results confirm that, despite producing high quality and high performance OSCs, spin-coating is unsuitable for high volume manufacturing due to the large amounts of materials and hazardous solvents wasted in the process. Blade-coating provides a good balance between low running costs, low environmental impact and decent performances but the process introduces lateral compositional gradients which could be detrimental for large area OSC processing. Spray-coating requires minimal initial investments but has relatively low performance and low manufacturing sustainability. Push-coating yields OSCs which perform as well as spin-coated ones, with a much lower environmental impact and cost. We should thus look forward to seeing whether this green and sustainable technology can develop into a large area coating process in the future

Ultrafast spectroscopy on water-processable PCBM: rod-coil block copolymer nanoparticles.

Using ultrafast spectroscopy, we investigate the photophysics of water-processable nanoparticles composed of a block copolymer electron donor and a fullerene derivative electron acceptor

k-Space Hyperspectral Imaging by a Birefringent Common-Path Interferometer

Fourier-plane microscopy is a powerful tool for measuring the angular optical response of a plethora of materials and photonic devices. Among them, optical microcavities feature distinctive energy-momentum dispersions, crucial for a broad range of fundamental studies and applications. However, measuring the whole momentum space (k-space) with sufficient spectral resolution using standard spectroscopic techniques is challenging, requiring long and alignment-sensitive scans. Here, we introduce a k-space hyperspectral microscope, which uses a common-path birefringent interferometer to image photoluminescent organic microcavities, obtaining an angle- and wavelength-resolved view of the samples in only one measurement. The exceptional combination of angular and spectral resolution of our technique allows us to reconstruct a three-dimensional (3D) map of the cavity dispersion in the energy-momentum space, revealing the polarization-dependent behavior of the resonant cavity modes. Furthermore, we apply our technique for the characterization of a dielectric nanodisk metasurface, evidencing the angular and spectral behavior of its anapole mode. This approach is able to provide a complete optical characterization for materials and devices with nontrivial angle-/wavelength-dependent properties, fundamental for future developments in the fields of topological photonics and optical metamaterials

Lévy defects in matrix-immobilized J aggregates : tracing intra-and intersegmental exciton relaxation

L.L. thanks the EC for financial support by the cofunded Amarout program and the Spanish Ministry for economy and competitiveness (plan nacional, Project MultiCrom (CTQ2014-58801)). G.C. acknowledges financial support by the European Research Council (ERC-2011-AdG No. 291198). D.G.L. and D.C. thank the UK EPSRC for funding via research grant EP/M025330/1 “Hybrid Polaritonics”One-dimensional J aggregates present narrow and intense absorption and emission spectra that are interesting for photonics applications. Matrix immobilization of the aggregates, as required for most device architectures, has recently been shown to induce a non-Gaussian (Lévy type) defect distribution with heavy tails, expected to influence exciton relaxation. Here we perform two-dimensional electronic spectroscopy (2DES) in one-dimensional J aggregates of the cyanine dye TDBC, immobilized in a gel matrix, and we quantitatively model 2DES maps by nonlinear optimization coupled to quantum mechanical calculations of the transient excitonic response. We find that immobilization causes strong non-Gaussian off-diagonal disorder, leading to a segmentation of the chains. Intersegmental exciton transfer is found to proceed on the picosecond time scale, causing a long-lasting excitation memory. These findings can be used to inform the design of optoelectronic devices based on J aggregates as they allow for control of exciton properties by disorder management.PostprintPostprintPeer reviewe

A core copolymer approach to improve the gain properties of a red-emitting molecule

We report a new approach to improve the gain characteristics of a red-emitting based molecule. The insertion of the active dye between two polymeric arms prevents the inter-molecular interactions deleterious for the gain. By means of the ultra-fast pump–probe technique we found an efficient energy transfer between the polymer and dye. High gain in the nanosecond timescale regime has been proved.info:eu-repo/semantics/publishe

New Organic Copolymer for Photonic Applications

info:eu-repo/semantics/nonPublishe

Strong collection of Amplified Spontaneous Emission with nematicons

Amplified spontaneous emission (ASE) generated in nematic liquid crystals is efficiently collected by a soliton generated in the same medium. The soliton guides and injects the weakly coherent polarized ASE into an optical fiber.info:eu-repo/semantics/publishe