In this paper, we report on an increase in emission intensity of up to 10 nW/mm2 that has been realized with a new novel two junction, diagonal avalanche control, and minority carrier injection silicon complementary metal–oxide–semiconductor (CMOS) light emitting device (LED). The device utilizes a four-terminal configuration with two embedded shallow nþp junctions in a p substrate. One junction is kept in deep-avalanche and light-emitting mode, while the other junction is forward biased and minority carrier electrons are injected into the avalanching junction. The device has been realized using standard 0.35 mm CMOS design rules and fabrication technology and operates at 9V in the current range 0.1– 3 mA. The optical output power is about one order of magnitude higher for previous single-junction nþp light-emitting devices while the emission intensity is about two orders of magnitude higher than for single-junction devices. The optical output is about three orders of magnitude higher than the low-frequency detectivity limit of silicon p–i–n detectors of comparable dimensions. The realized characteristics may enable diverse optoelectronic applications in standard-CMOS-silicon-technology-based integrated circuitry.

No description available.

We have developed high-efficiency blue organic light-emitting devices incorporate 1,3,5-Tri(1-pyrenyl)benzene(TPB3) as emitting layer and 4,7-diphenyl-1,10-phenanthroline(BPhen) as the electron transporting layer, which has a large Highest Occupied Molecular Orbital energy level and has good electron mobility. A device having the configuration : ITO(140 nm)/NPB(65 nm)/(TPB3 40nm)/BPhen(30 nm)/LiF(0.8 nm)/Al(200 nm) exhibited a maximum luminance at 9.5V of 29940 cd/m2, The maximum current and power efficiencies were 3.85 cd/A and 2.38 lm/W, respectively. The current and power efficiencies were greater than 3cd/A and 1.1 lm/W respectively, Over a large range of potentials (3.5~10.0V) with good Commission Internationale de l¡¦Eclairage (CIE) coordinates of (0.17, 0.22). These results indicate that TPB3 is good blue-emitting material for OLED applications. The photophysical and chemical properties of TPB3 have also been studied in this research.

Over the past decade, intensive academic and commercial interests have been paid on compounds possessing photochemical properties, namely for their preparation, chemical properties, high efficiency and potential low-cost. Compounds having intense photochemical properties gained great interest due to wide range of potential applications. The sensitizers are one of the key components for high power-conversion efficiency in the dye sensitized solar cells (DSSCs). They are the core components in the organic light-emitting devices (OLEDs) due to their ability to emit light with the wavelengths largely red- shifted from their absorption wavelength. Ruthenium based sensitizers have been tagged “molecular light switches” because, although the fluorescence of these complexes in aqueous solutions is negligible, it increases of greater than 10000 fold in the presence of DNA. Many polypyridyl and dipyrido phenazine ruthenium complexes have achieved high power conversion efficiencies and therefore are of practical interest. Several research groups stated that the dipyrido phenazine ligand may be thought of as comprising two components: a bipyridyl unit and a phenazine unit. These two subunits behave essentially separately, with many molecular orbitals being localised over only one subunit and a redox properties of central phenazine moiety in the dipyrido phenazine ligand are important for the photochemical applications. Therefore a phenazine ligand was selected as a model for the present investigation. The chemistry of phenazine ligand is mostly limited to the late transition metal and f - element complexes. Our laboratory has a rich backgroung in the aluminum and early transition metal chemistry. The aluminum chemistry and early transition metal chemistry are of great interest since aluminum and early transition metal complexes are environmentally friendlier and cheaper than the late transition metal compounds. Another drawback of the ruthenium-based sensitizers is the lack of absorption in the red region of the visible spectrum, and also low molar extinction coefficients. An essential requirement for efficient conversion of solar energy is the good spectral match of the sensitizer absorption to the emission spectrum of solar radiation. In this regard, the ruthenium sensitizers’ spectral response in the lower energy regions is not sufficient. The current project has three parts. In the first part we collected and reviewed known literature regarding the certain classes of non-innocent ligands containing the six-membered carbon- nitrogen heterocycles and regarding the ligands potentially important for the photochemical applications. We also reviewed all available to the data information about the complexes supported by the phenazine ligand. In the second part we have investigated interaction of alkylaluminum compounds and phenazine and observed reduction of phenazine accompanied by formation of dialuminum cage type compounds containing two formally mononegative phenazine ligand. The derivatization of phenazine has been also observed. It resulted in formation of compounds having a stable organic radical. In a third part of our project we have explored interaction of phenazine or thiophenazine with the alkylaluminum compounds and chromium dichloride. The reaction in the three component system resulted in reduction of phenazine ligand and lead to the heterometallic Cr(II) - aluminum complexes containing a formally dinegative phenazine or thiophenazine ligands. When a large excess of triethylaluminum was taken, reduction of phenazine and chromium has been observed leading to the heterometallic multinuclear Cr(I) - aluminum complex containing a formally dinegative phenazine ligands and two chromium atoms in one complex in the rare oxidation state one.

Over the past decade, intensive academic and commercial interests have been paid on compounds possessing photochemical properties, namely for their preparation, chemical properties, high efficiency and potential low-cost. Compounds having intense photochemical properties gained great interest due to wide range of potential applications. The sensitizers are one of the key components for high power-conversion efficiency in the dye sensitized solar cells (DSSCs). They are the core components in the organic light-emitting devices (OLEDs) due to their ability to emit light with the wavelengths largely red- shifted from their absorption wavelength. Ruthenium based sensitizers have been tagged “molecular light switches” because, although the fluorescence of these complexes in aqueous solutions is negligible, it increases of greater than 10000 fold in the presence of DNA. Many polypyridyl and dipyrido phenazine ruthenium complexes have achieved high power conversion efficiencies and therefore are of practical interest. Several research groups stated that the dipyrido phenazine ligand may be thought of as comprising two components: a bipyridyl unit and a phenazine unit. These two subunits behave essentially separately, with many molecular orbitals being localised over only one subunit and a redox properties of central phenazine moiety in the dipyrido phenazine ligand are important for the photochemical applications. Therefore a phenazine ligand was selected as a model for the present investigation. The chemistry of phenazine ligand is mostly limited to the late transition metal and f - element complexes. Our laboratory has a rich backgroung in the aluminum and early transition metal chemistry. The aluminum chemistry and early transition metal chemistry are of great interest since aluminum and early transition metal complexes are environmentally friendlier and cheaper than the late transition metal compounds. Another drawback of the ruthenium-based sensitizers is the lack of absorption in the red region of the visible spectrum, and also low molar extinction coefficients. An essential requirement for efficient conversion of solar energy is the good spectral match of the sensitizer absorption to the emission spectrum of solar radiation. In this regard, the ruthenium sensitizers’ spectral response in the lower energy regions is not sufficient. The current project has three parts. In the first part we collected and reviewed known literature regarding the certain classes of non-innocent ligands containing the six-membered carbon- nitrogen heterocycles and regarding the ligands potentially important for the photochemical applications. We also reviewed all available to the data information about the complexes supported by the phenazine ligand. In the second part we have investigated interaction of alkylaluminum compounds and phenazine and observed reduction of phenazine accompanied by formation of dialuminum cage type compounds containing two formally mononegative phenazine ligand. The derivatization of phenazine has been also observed. It resulted in formation of compounds having a stable organic radical. In a third part of our project we have explored interaction of phenazine or thiophenazine with the alkylaluminum compounds and chromium dichloride. The reaction in the three component system resulted in reduction of phenazine ligand and lead to the heterometallic Cr(II) - aluminum complexes containing a formally dinegative phenazine or thiophenazine ligands. When a large excess of triethylaluminum was taken, reduction of phenazine and chromium has been observed leading to the heterometallic multinuclear Cr(I) - aluminum complex containing a formally dinegative phenazine ligands and two chromium atoms in one complex in the rare oxidation state one.

No description available.

Due to its truly two dimensional (2D) character and its particular lattice, single layer graphene (SLG) possesses exceptional properties: it is semimetallic, transparent, strong yet flexible ... Complementary features such as the insulating character of hexagonal boron nitride (h-BN) and semiconducting properties of transition metal dichalcogenides (TMDs) enable the whole spectrum of electronic devices to be built with combinations of these 2D materials. Due to this and the ease of exfoliation with a sticky tape, a vast amount of research was sparked. The mechanical exfoliation method, however, is only suitable for novel or proof-of-concept devices. The trend nowadays in electronics is towards transparent, lightweight, flexible, embedded smart devices and sensors in everyday objects such as windows and mirrors, garments, windshields, car seats, parachutes...These demands are already met inherently by these new materials, thus the challenges remaining are within their synthesis, deposition and processing, where more scalable ways of production and device fabrication need to be developed. This thesis explores innovative approaches using established techniques that aim to bridge the gap between proof-of-concept devices and real applications of 2D materials in future commercial level technologies. Methods to create graphene and engineer its properties are employed with a special focus on scalability and adaptability towards the industry. These graphene materials have been processed using pioneering schemes to create different optoelectronic devices and sensors. The techniques employed here for synthesis, transfer and deposition, device processing and characterization of graphene and derivatives, are suitable for their use in large manufacturing and mass-production. Depending on the application envisaged, different materials are used and optimize in order to balance good performance, cost-effectiveness and suitability/scalability of the process for the specific target the device was designed for.

This thesis focuses on development of novel nanomaterials, including semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs), for fabricating white-light emitting devices and assaying thiols in biological and environmental samples. The thesis mainly contains two divisions. One demonstrates synthesis, optical properties and white-light emissions of alloyed quantum dots and their application to light-emitting devices. The other describes to combine functionalized gold nanoparticles with capillary electrophoresis and accomplish high selectivity and ultrasensitive detection for thiols. First, through one-step aqueous synthesis, alloyed ZnxCd1¡VxSe QDs have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO4)2 and Zn(ClO4)2 with NaHSe using 3-mercaptopropionic acid as a surface-stabilizing agent. The optical properties and composition of the alloyed QDs were highly dependent on the molar ratio of Zn2+ to Cd2+. With the increase in Zn content, a systematic blue shift occurred in the first exciton absorption and band edge emission. Moreover, X-ray diffraction peaks of the alloyed QDs systematically shifted to larger angles simultaneously. These systematic shifts indicated the formation of the alloyed QDs. Interestingly, among these alloyed QDs, Zn0.93Cd0.07Se QDs exhibited white-light emission with quantum yields of 12%. In addition, we discovered that we could adjust the relative strength of the band edge and trap state emissions by controlling the reaction time, thereby attain white-light-emitting QDs. Finally, we blended alloyed QDs with ultraviolet-transparent polydimethylsiloxane (PDMS) to develop a white-light, solid-state lighting device by using a 365-nm UV lamp as the pump source. In the other part of this thesis, we proposed a method for selective enrichment of thiols using Tween 20-capped gold nanoparticles (AuNPs) prior to capillary electrophoresis coupled with laser-induced fluorescence (CE-LIF). By forming Au-S bonds, Tween 20-AuNPs can selectively extract thiols from a complicated matrix. A Tween 20 capping layer not only suppresses nonspecific adsorption, but also enables NPs to disperse in a highly-salinity solution. For analyses of aminothiols, after extraction and centrifugation, thioglycollic acid was utilized to remove aminothiols that attached to the NP surfaces. The extracted aminothiols was derivatized with o-phthalaldehyde (OPA) followed by CE-LIF. The use of this nanoprobe provided approximately 11-, 282-, and 21-fold sensitivity improvements for homocysteine (HCys), glutathione (GSH), and £^-glutamylcysteine (GluCys), respectively. Furthermore, the limits of detection (LODs) at a signal-to-noise ratio of 3 for HCys, GSH, and GluCys are 4013, 80, and 383 pM, respectively. A practical analysis of aminothiols in human urine sample has been accomplished by our proposed method. For another application to determining thiol-containing peptides, we use dithiothreitol to remove thiol-containing peptides from the NP surface through ligand exchange. The released peptides are selectively derivatized with OPA to form tricyclic isoindole derivatives. After injecting a large sample volume, the sensitivity of these peptides was improved by stacking them via using polyethylene oxide (PEO) as additive for on-line concentration and separation. As a result, LODs for GSH, GluCys, and phytochelatins (PC2 ~ PC4) were down to 0.1-6 pM. The proposed method has the lowest LODs for five peptides compared to other reported methods, and it also detect dissolve thiols in seawater in practice. Our proposed method is capable of ultrasensitive detection for thiols in biological and environmental samples.

The development of ultraviolet semiconductor emitters (LEDs and lasers) will enable a large number of industrial and medical applications. AlGaN alloys are ideally suited for the development of such devices since their energy gap can be tuned from the near UV (365 nm) to deep UV (200 nm). However, the doping of such materials n- and p-type is difficult. Another problem is the generally poor light extraction efficiency from both UV and visible LEDs. This research addressed the first problem by developing UV emitters in the form of graded-index-separate-confinement-heterostructure (GRINSCH). In these device the active region is embedded in two compositionally graded wave guiding layers. Due to the polar nature of nitride semiconductors these compositionally graded AlGaN films are doped p- or n-type if the grading changes from high to low concentration or from low to high concentration respectively. Thus, a p-n junction is automatically formed without the incorporation of dopants. The polarization induced doping level in these structures was calculated to be 1018cm-3 for the p- and n-sides. A number of devices, whose active region is either 75 nm Al0.72Ga0.28N bulk film or multiple QWs have been grown on 6H-SiC substrates by Molecular-Beam Epitaxy (MBE) and investigated. The emission properties of these structures were investigated by cathodoluminescence (CL) and by measuring their optical gain. A maximum net modal gain in excess of 80 cm-1 was measured with an optical gain threshold of 14 µJ / cm2. Some of these structures, emitting in the near UV, were also electrically pumped. The second problem was addressed by incorporating dielectric (TiO2) photonic crystals on the phosphor plates of white LEDs in order to increase the light extraction efficiency upon illumination with blue LEDs. The two-dimensional (2D) hexagonal-lattice of TiO2 photonic crystal was formed by e-beam lithography on low-scattering (Y1-xCex)3Al5O12 (YAG:Ce) ceramic phosphor plates. Yellow light extraction enhancement by a factor of 4.4 was achieved with a 2D photonic crystal nano-cylinders having diameter 430 nm, lattice constant of 580 nm and height of 350 nm. Simulations using a three-dimensional finite difference time domain are consistent with our measured data.

No description available.