We have mixed nematic light-emitting liquid crystals and incorporated them as insoluble cross-linked polymer networks in a liquid crystal white-light organic light-emitting diode (LC-WOLED). The light emission is not voltage-dependent and polarized white light emission is also demonstrated. This wetchemistry approach to WOLEDs is compatible with patterning by photolithography as well as by inkjet printing at room temperature on plastic substrates by roll-to-roll manufacturing.

Titanium dioxide nanorods coated with phosphonate ligands with photoreactive coumarin in a terminal position were prepared. These nanorods form liquid crystalline solutions at high concentrations. Relatively high dielectric constant thin films were prepared from the solution-processable and photocrosslinkable hybrid inorganic/organic titanium dioxide nanorods.

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We discuss a liquid crystal composite approach to provide a distributed interface to vertically separate electron-donating and electron-accepting films in an organic photovoltaic device. Two different methods are used to prepare a nematic liquid crystal polymer network with a porous surface and electron-donating properties. This is infilled with an electron-accepting organic semiconductor to form a bilayer device. The interface is diffuse rather than localized so that more photogenerated excitons can reach it to generate charge before they recombine. Photoinduced absorption of a blend of the donor and acceptor materials confirms that excitons dissociate at the heterointerface. The spatial features of the diffuse interface are examined by Fourier analysis of topographic images. We find a correlation between the in-plane spatial frequencies of the interface and photovoltaic device performance. The device performance is investigated as a function of input irradiance. Any charge combination is monomolecular rather than bimolecular, and the monochromatic power conversion efficiency varies between 0.8% and 0.3% with input irradiance. Equivalent circuit analysis shows that this is limited by a high series resistance, a blocking contact, and nonoptimized spatial features of the porous interface.

We report a new single-step method to directly imprint nanometer-scale structures on photoreactive organic semiconductors. A surface relief grating is spontaneously formed when a light-emitting, liquid crystalline, and semiconducting thin film is irradiated by patterned light generated using a phase mask. Grating formation requires no postannealing nor wet etching so there is potential for high-throughput fabrication. The structured film is cross-linked for robustness. Gratings deeper than the original film thickness are made with periods as small as 265 nm. Grating formation is attributed to mass transfer, enhanced by self-assembly, from dark to illuminated regions. A photovoltaic device incorporating the grating is discussed.