Successful integration of solution-processible nanocrystal quantum dots, active over a wide spectral range in the infrared, organic molecules and polymers, to fabricate efficient photoconductive and photorefractive devices operational at important optical communication wavelengths is achieved. Sensitization of the polymeric composites by quantum dots led to high photocurrents at 1340 nm, yielding a high photoconductive quantum efficiency. In the photorefractive composites, pronounced two-beam coupling was observed, leading to good optical gains achievable by low-power continuous-wave illumination. The photoresponse was further extended to 1550 nm. A steady state diffraction efficiency was obtained in the dynamic refractive-index gratings with appreciable response times. In order to enhance the photoconductive performance of the devices, the organic semiconductor pentacene was incorporated into the hybrid composite through a soluble presursor. At the operating wavelength of 1340 nm, the photocurrent increased significantly as the amount of pentacene in the composite was increased, resulting in a spectacular improvement of external quantum efficiency.

We demonstrate the functionalization of 2-D photonic crystal structures operating at ∼ 1.5 μm with colloidal PbSe quantum dots and examine the modified photoluminescence from the functionalized photonic crystal. Using spin coating and airbrushing, monodisperse PbSe quantum dots were deposited from hexanes on lithographically patterned GaAs photonic crystal substrates. The effectiveness of patterning the PbSe quantum dots via standard liftoff process was examined. The near-IR photoluminescence spectra of quantum dot-functionalized photonic crystals were studied. We found that the photoluminescence peak became attenuated by approximately a factor of five and exhibited a narrow peak width (50 nm vs. 120 nm) compared to PbSe deposited on unpatterned GaAs, suggesting that there is some coupling between the quantum dots and the photonic crystal. Future work to improve the coupling and detection efficiency is proposed.

In order to design liquid lens which works in a severe environment such as high temperature and high humidity, several layered liquid systems are investigated. Especially, the change of the interface between conducting and non-conducting liquid layers has been traced by using empirical molecular dynamics simulation and density-functional theory calculation. The stability of the liquid layers at high temperature was evaluated by simulation results such as the density profile of liquid components, their distribution near the interface, the interface thickness and chemical reactivity between them, which depends on the molecular species consisting of liquid and their concentrations. We found that the organic solvent including halogen atoms, alkyl halide, easily penetrates into conducting liquid layer and reacts with its substances, which is added to increase refractive index and density of non-conducting liquid. We also presented an optimized solution including the minimum organic solvent and satisfying the requisites for an optical device.

A polymer field-effect transistor (FET) was fabricated with poly(3-hexylthophene) as an active layer and poly(methyl-methacrylate) gate dielectric modified with poly(vinyl alcohol). The influences of air atmosphere on the FET property were investigated. Under the air atmosphere, FET properties such as modulation of drain current by gate bias, leakage current and threshold voltage shift were strongly influenced by humidity. An influence was investigated by temperature dependence of FET properties. It cleared the relationship between the FET property and intrinsic mobile ion in the gate dielectric. The influence of humidity on the FET property can be prevented by insertion of a clay mineral layer, which clogs motion of ion transport in gate dielectric layer.

The motivation and distinct approach for this work is the use of intraband transitions within colloidal quantum dots for the detection of mid- (3-5 μm) and/or long-wave (8-14 μm) infrared light. The CdSe colloidal quantum dot/MEH-PPV conducting polymer nanocomposite material is well-suited for this application due to the ∼1.5 eV difference between the corresponding electron affinities. Therefore, CdSe colloidal quantum dots embedded in MEH-PPV should provide electron quantum confinement such that intraband transitions can occur in the conduction band. Further, it is desirable to deposit these nanocomposites on semiconductor substrates to enable charge transfer of photogenerated electron-hole pairs from the substrate to the nanocomposite. In this way, optoelectronic devices analogous to those achieved using Stranski-Krastanow quantum dots grown by epitaxy can be realized. To date, there have been relatively few investigations of colloidal quantum dot nanocomposites deposited on GaAs substrates. However, it is crucial to develop a better understanding of the optical properties of these hybrid material systems if such heterostructures are to be used for optoelectronic devices, such as infrared photodetectors. By depositing the nanocomposites on GaAs substrates featuring different doping characteristics and measuring the corresponding Fourier transform infrared absorbance, the feasibility of these intraband transitions is demonstrated at room temperature.

Intercalated or exfoliated nanocomposites were composed by the novolac cured epoxy and one of three different kinds of layered silicates, such as montmorillonite (PK-802), saponite (Semecton-SA) and nontronite (PK-805). The bi-functional modifiers (PI/BEN or MI/BEN) with different ratio, which contained one of the promoters (2-phenylimidazole, PI and 2-methylimidazole, MI) of epoxy and benzalkonium chloride (BEN), were intercalated into the gallery regions of pure clays at the same time and followed by a crosslinking reaction. The properties of novolac cured epoxy/clay nanocomposites were characterized by wild-angle X-ray diffraction (WAXRD), thermal analysis (TGA/DSC), coefficiency of thermal expansion (TMA), mechanical properties (DMA), and transmission electron microscopy (TEM). According to the measurement, these novolac cured epoxy-clay nanocomposites have shown the significant improvement in the thermal, mechanical and barrier properties.

Transmission volume holograms recorded in two types of methacrylate-based photopolymer films that include benzyl n-butyl phthalate (BBP) or Poly(methyl methacrylate) (PMMA) are studied. It is shown that both BBP and PMMA molecules can be uniformly dispersed into methacrylate monomers and that a refractive index modulation as high as ∼0.005 is recorded by optimizing their volume concentrations. Moreover, it is also shown that the additional doping of silica nanoparticles substantially suppresses polymerization shrinkage without increasing optical scattering loss.

Double layer structures of porous silicon (PS) and polypyrrole (PPy) were prepared in order to study their electrical properties. PS was prepared by electrochemical etching in a HF/Ethanol solution from n-type silicon wafer and PPy by galvanstatic method in a lithium perchlorate/monomer solution. The experimental parameters for preparation of PS and PPy were varied to obtain different morphology of the PS/PPy structures. The surface topography of these structures was analyzed by Atomic Force Morphology (AFM). Tip- and agglomerate-like morphologies of PPy were obtained on PS layers with different pore diameters. The electrical and AFM characterization of PS were studied with and without PPy. Current-voltage (I-V) curves of PS/PPy structures were obtained in dark and under illumination. PS without PPy shows an exponential behavior in the current ((+)Al/n-Si/PS/Cu(-)), but it is almost linear when the PPy layer is deposited over the PS layer ((+)Al/n-Si/PS-PPy/Cu(-)). All structures present photovoltage under illumination conditions. However, this parameter is smaller in Al/n-Si/PS-PPy/Cu structure than Al/n-Si/PS/Cu. The open circuit voltage (VOC) and short circuit current density (JSC) of these structures decrease when the surface morphology of PPy is tip-like, but JSC increase when the surface morphology of PPy is agglomerate-like.

Luminescent stilbenoid chromophores with two alkoxysilane end groups are prepared via hydrosilylation or condensation / reduction of substituted 5-ring OPVs with hydro- and aminopropylsilanes. Chromophore and curable units are connected via flexible spacers. To obtain compounds with a rigid connection between silane and π-system, iodo- or bromo-OPVs were coupled to alkoxysilanes carrying vinyl- or p-vinylphenyl moieties under Heck conditions. This approach allowed a combined connection of the chromophore to the silane moiety with an extension of the π-system. Hydrolysis of the alkoxysilanes yields silanols condensing to curable three-dimensional networks, thus allowing the transformation of small molecules to transparent and fluorescent films with well-defined chromophores.