E.A. Marseglia

Crystal network formation in organic solar cells

We have studied the effects of annealing on performance and morphology of photovoltaic devices using blends of two organic semiconductors: a conjugated polymer and a soluble perylene derivative. The efficiency of such photovoltaic cells has been determined. The effect of temperature on blend morphology has been investigated for actual device films. Annealing leads to the formation of micron size perylene crystals and an enhancement of the quantum efficiency. This enhancement has been attributed to the formation of an electron conducting perylene crystal network.

Dye-based donor/acceptor solar cells

We have fabricated organic donor/acceptor solar cells with three different architectures using soluble derivatives (dyes) of the molecular semiconductors phthalocyanine as electron donor (D), i.e. hole transport material and perylene as electron acceptor (A), i.e. electron transport material. These architectures comprise a blend and a double layer structure as well as the only recently reported laminated-device structure. The organic semiconducting films were deposited at room temperature via spin coating from solution. Current–voltage (I/V) characteristics and external quantum efficiency spectra will be discussed. The measured quantum efficiencies reach values between 0.3% and 1.1% with a photoresponse covering the entire spectrum of visible light. Our results show that together with insoluble small molecules (pigments) and conjugated polymers, dye molecules represent a new class of organic semiconducting materials that can be used to manufacture D/A solar cells.

Photovoltaic properties of MEH-PPV/PPEI blend devices

Abstract We report on the photophysical properties of blends of poly(2-methoxy-5-(2′-ethyl-hexyloxy)- p -phenylene vinylene), MEH-PPV, and perylene bis(phenethylimide), PPEI. Highly efficient quenching of photoluminescence (PL) efficiency was observed. We have measured the photocurrent response of an MEH-PPV/PPEI blend in a sandwich cell between indium tin oxide (ITO) and aluminium electrodes. The external quantum efficiency (EQE) is enhanced considerably with regard to single layer MEH-PPV devices.

Structural studies of oriented precursor route conjugated polymers

Abstract Conjugated polymers prepared by the thermal transformation of a precursor polymer can be produced as highly oriented films if the transformation reaction is carried out in a stress field. Investigation of the anisotropic properties of such films has given much information on the microscopic electronic processes which determine the behaviour of these polymers. We report here on the structural characterisation of oriented poly(phenylenevinylene) [PPV] and Durham-route polyacetylene [(CH) x ] using X-ray diffraction and infrared spectroscopy.

Synthesis and optical characterisation of platinum(ii) poly-yne polymers incorporating substituted 1,4-diethynylbenzene derivatives and an investigation of the intermolecular interactions in the diethynylbenzene molecular precursorsElectronic supplementary information (ESI) available: atomic cooordinates for 6 and 7. See http://www.rsc.org/suppdata/nj/b2/b206946f/

A series of 1,4-diethynylbenzene (1) derivatives, H–CC–R–CC–H with R=C6H3NH2 (2), C6H3F (3), C6H2F2-2,5 (4), C6F4 (5), C6H2(OCH3)2-2,5 (6) and C6H2(OnC8H17)2-2,5 (7) has been synthesised and their crystal structures determined by single crystal (2–5) or powder (6, 7) X-ray diffraction. The CCH⋯πCC hydrogen bonds dominating structure 1 are gradually replaced by CC–H⋯F ones with the increase of fluorination (3→5), or completely replaced by CCH⋯N and NH⋯πCC bonds in 2, and CCH⋯O in 6 and 7. The related platinum-based polymers, trans-[–Pt(PnBu3)2–CC–R–CC–]n (R=as above and C6H4,) have been prepared and characterised by spectroscopic methods and thermogravimetry, which show that the amino- and methoxy-derivatives have lowest thermal stability while the fluorinated ones exhibit increasing thermal stability with increasing fluorination. Optical spectroscopic measurements reveal that substituents on the aromatic spacer group do not create strong donor–acceptor interactions along the rigid backbone of the organometallic polymers.

Solid State Conformation and Crystal Packing of Methyl-Substituted Quaterthiophenes

Abstract The solid state structures of a series of methyl substituted neutral quaterthiophenes have been analysed. Structures have been retrieved from the Cambridge Structural Database and investigated in terms of crystal cohesion and intermolecular interactions. In these thiophene oligomers, it can be shown that crystal packing efficiency and optimisation of S—S, C-H—S and C-H—π interactions constitute the driving force for their solid state geometry and configuration. A detailed discussion of their packing arrangement is reported and shown to be based on either a herringbone or π-π stacking of thiophene units.

Structural and morphological investigations of oriented Durham polyacetylene

Abstract Trans -polyacetylene films have been synthesized via the Durham precursor route, and have been oriented by application of stress during preparation from the precursor polymer. X-ray and electron diffraction measurements show that these Durham polyacetylene films are composed of crystallites that are highly oriented about the fibre axis. The crystallite size perpendicular to the chains and the nature of the lateral packing have been derived from a line profile analysis of hk 0 reflections according to the paracrystalline model. The results have been verified by direct Fourier synthesis of the observed intensities of hk 0 reflections.

Structural characterisation of a series of acetylide-functionalised oligopyridines and the synthesis, characterisation and optical spectroscopy of platinum di-ynes and poly-ynes containing oligopyridyl linker groups in the backbone

A series of trimethylsilyl-protected bis(ethynyl)oligopyridine derivatives Me3SiCC–R–CC–SiMe3 (R = 2,2′-bipyridine-5,5′-diyl (1a), 2,2′-bipyridine-6,6′-diyl (2a), 2,2′:6′,2″-terpyridine-6,6″-diyl (3a), 4′-phenyl-2,2′:6′,2″-terpyridine-6,6″-diyl (4a)) has been synthesised and 2a–4a have been characterised by single crystal X-ray crystallography. The corresponding terminal di-ynes H–CC–R–CCH (1b–4b) and their dinuclear platinum(II) complexes trans-[(Et3P)2(Ph)Pt–CC–R–CC–Pt(Ph)(Et3P)2] (1M–4M) have been characterised spectroscopically and by single-crystal X-ray crystallography for 2M. Novel platinum(II) poly-yne polymers trans-[Pt(PBun3)2–CC–R–CC–]n (1P–4P) containing the oligopyridyl linker groups in the backbone have been synthesised by the CuI-catalysed dehydrohalogenation polycondensation reaction of 1b–4b and trans-[(Bu3P)2PtCl2] in Pri2NH–CH2Cl2. The polymeric materials exhibit decreasing thermal stability with increasing number of pyridine units in the linker group. In the absorption and phosphorescence spectra, the platinum(II) poly-yne and di-yne complexes 1P, 1M show red shifts whereas the complexes 2P–3P, 2M–3M show blue shifts of the S1 and T1 states. At room temperature, the phosphoresence spectra indicate some excimer formation whereas at 10 K, only intra-chain emission occurs. The results of the photophysical studies are compared with those obtained for other platinum(II)-containing poly-ynes and related organometallic polymers.

Structural order in poly(p-phenylene vinylene)

Poly(p-phenylene vinylene) [PPV] is fast becoming one of the most widely studied of the conjugated polymers. Its preparation via a precursor polymer synthesis allows ready processing and presents many opportunities for subtle control of the physical and electronic properties of the final polymer. A number of precursor routes have now been developed and we report an X-ray and electron diffraction study of the effects of different synthesis routes on the structure of the PPV polymer films thus prepared.

The effect of side groups on the structure and ordering of poly(p-phenylene vinylene) derivatives

Abstract Results of electron diffraction experiments on unoriented and stretct-oriented poly( p -phenylene vinylene) [PPV], poly(2,5-dimethyl- p -phenylene vinylene) [PDMePV], poly(2,5-dimethoxy- p -phenylene vinylene) [PDMeOPV] and poly(2,5-diethoxy- p -phenylene vinylene) [PDEOPV] are presented. We make a comparison of these closely related materials and discuss the effect that different 2,5-substituent groups have on the state of order.