Photovoltaic devices consisting of a blend of poly(9,9'-dioctylfluorene- co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) with poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) and light-emitting diodes comprising a blend of F8BT with poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) were fabricated. The lateral phase separation in both blend films spin coated from p-xylene solution was typically a few microns but by inkjet printing a solution of identical composition, the feature size could be reduced to about 300 nm when combined with raised substrate temperature during the printing process. Light-emitting diodes of TFB:F8BT blend showed good performances and higher efficiency than spin coated devices at high voltages. Inkjet printed photovoltaic devices of both TFB and PFB blends showed a much higher efficiency than those prepared by spin coating, mainly because of the finer phase separation promoted by inkjet printing. 21 refs.

Poly((9,9-dioctylfluorene-2,7-diyl)-co-(4-dicyanomethylene-2-methyl-6-(4- (diphenylamino)styryl)-4H-pyran-4',4''-diyl)) copolymers bearing dicyanomethylene (DCM) moieties as pendants, were synthesised by a palladium-catalysed Suzuki coupling reaction. The copolymers showed good solubility in common organic solvents, moderately high glass transition temperatures (greater than 97C) and good thermal stability. The UV vis absorption spectra of three copolymers showed two major absorptions by the main chain (380 nm) and by the DCM units (485 nm) and the long-wavelength absorption increased with increasing DCM comonomer fraction. The photoluminescence spectra in chloroform solution showed main chain emission at 420 nm and DCM unit emission at 620 nm but in the solid state, the photoluminescence spectra of the copolymers showed only the long wavelength red emission at 620 nm. An energy transfer mechanism was thought to be responsible for this. The electroluminescent efficiency of light-emitting diodes containing the copolymers decreased dramatically with increasing DCM content. Electroluminescent efficiencies were significantly improved when bilayer devices were fabricated in which a thin layer of electron transporting tris(8-hydroxyquinolinato)aluminium was inserted between the emitting polymer layer and the cathode. 43 refs.

Poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta(def)phenanthrene)) (PCPP), an electroluminescent polymer with stabilised blue emission, was synthesised from 4H-cyclopenta(def)phenanthrene. The photoluminescence spectra of the polymer did not show any peak in the long wavelength region, even after annealing for 18 h at 150C in air. A light-emitting diode (LED) with a configuration of indium tin oxide/polyethylene dioxythiophene:polystyrene sulphonate/PCPP/Al generated electroluminescent emission with high maximum brightness (1500 cd/sq.m at 14 V), high efficiency (0.70 cd/A at 180 mA/cu.cm), maximum peak at 400 nm, low turn-on voltage of 6.0 V, and excellent CIE coordinates for the blue colour without any filtering. PCPP showed stabilised blue electroluminescence emission without any low energy emission band in the region of 500-600 nm even after annealing for 18 h at 150C or operation of the device for 40 min. 27 refs.

Four diyne-containing poly(p-phenylene vinylene)s were synthesised by polycondensation reactions. Differences in the degree of polymerisation were attributed to differences in the reactivity of the different reactive groups during polycondensation. The absorption and emission spectra in dilute chloroform solution and the thin film absorption spectra depended on the degree of polymerisation. The photophysical and electrochemical properties of the polymers were similar to those of their yne-containing counterparts, despite the differences in the backbone conjugation pattern. Introducing a second yne unit lowered the highest occupied molecular orbit and lowest unoccupied molecular orbit levels, so the electron affinity of the diyne-containing polymers was greater than that of the yne-containing polymers. The introduction of the second yne unit facilitated the movement of charges during the electrochemical processes leading to minimal discrepancy between the optical and electrochemical band gap energies. The yne-containing polymers, however, showed significant side-chain dependent differences between the between the band gap energies. Light-emitting diodes of the configuration indium tin oxide/polyethylene dioxythiophene:polystyrene sulphonate/diyne- containing polymer/Ca/Al showed low turn-on voltage between 2 and 3 V because of enhanced electron affinity. 30 refs.

Preparation of a series of light emitting polyquinolines containing 9,9'-spirobifluorene units, using Friedlander reactions, is described. Characterisation was carried out using Fourier transform infrared and nuclear magnetic resonance spectroscopies, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction. Optical and electrochemical properties were evaluated using photoluminescence and electroluminescence spectroscopy, and cyclic voltammetry. It was observed that the spiro moieties reduced interchain aggregates and effectively controlled conjugation length, allowing good control of electronic and electroluminescent properties. Emission colours from blue to yellow could be achieved. 28 refs.

Preparation of semiladder polyphenylenes containing carbazole and fluorene moieties, and with ladder type tetraphenylene and hexaphenylene structures in the main chain, is described. Characterisation was carried out using gel permeation chromatography, Fourier transform infrared, nuclear magnetic resonance and ultraviolet visible spectroscopies, thermogravimetric analysis, differential scanning calorimetry, and electrical cyclic voltammetry measurements. It was observed that polymers exhibited pure blue fluorescence in solution, and also when prepared into light emitting devices. 19 refs.

Highly oriented blue-light-emitting blended films based on polydioctylfluorene (PFO) and ultrahigh molecular weight polyethylene (UPE) were prepared by a tensile deformation method. Effects of PFO molecular weight, blend composition, draw ratio of film, and excitation with polarised or unpolarised light on dichroic ratio were evaluated and discussed, and a figure of 58 for polarised photoluminescence was obtained when PFO molecular weight was fairly low and at low concentration range. Characterisation of films utilised ultraviolet visible and fluorescence spectroscopy measurements. 29 refs.

Introduction of a heteroaryl moiety, oxadiazole, as a branching unit during the Suzuki polycondensation of a polyfluorene resulted in a polymer for use in polymer light emitting diodes (PLEDs) giving a very stable blue light emission. Synthesis, characterisation, and optical properties were described. Polymers were characterised using gel permeation chromatography, differential scanning calorimetry and nuclear magnetic resonance, photoluminescence, and ultraviolet absorption and emission spectroscopies. PLEDs were evaluated by their electroluminescence and photoluminescence spectra. 21 refs.