The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

Lanthanide ions possess fascinating optical properties and their discovery, first industrial uses and present high technological applications are largely governed by their interaction with light. Lighting devices (economical luminescent lamps, light emitting diodes), television and computer displays, optical fibres, optical amplifiers, lasers, as well as responsive luminescent stains for biomedical analysis, medical diagnosis, and cell imaging rely heavily on lanthanide ions. This critical review has been tailored for a broad audience of chemists, biochemists and materials scientists; the basics of lanthanide photophysics are highlighted together with the synthetic strategies used to insert these ions into mono- and polymetallic molecular edifices. Recent advances in NIR-emitting materials, including liquid crystals, and in the control of luminescent properties in polymetallic assemblies are also presented. (210 references.)

Taking advantage of luminescent lanthanide ions

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

/pdf/lanthanide-luminescence-for-functional-materials-and-bio-1w9cppwf8r.pdf

Lanthanide luminescence for functional materials and bio-sciences

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

The structural and luminescence properties of porous silicon

The photoluminescence (PL) properties of ZnSe films grown by hot wall epitaxy are reported. The PL spectra show clear neutral donor-bound exciton peak; donor acceptor pair (DAP) peak, conduction band to acceptor (CA) peak, and their phonon replicas until fourth order. The conduction band to acceptor peak and it's phonon replicas exist until room temperature. From the ratio of PL intensities of DAP and CA peaks and their replicas, we obtain the Huang-Rhys factor S = 0.58, in agreement with other experiments for acceptor-bound exciton transitions. From the temperature dependence of PL intensities we derive the activation energy of thermal quenching process for the DAP transitions as about 7 meV.

Luminescence properties of ZnSe films grown by hot wall epitaxy

The present disclosure relates to display, windows, camera cover, lens and lens cover, optical/infra-red sensors, glasses and spectacles.

Carbon-based Nano-thin Film for Enhancing Surface Abrasion Resistance on Sapphire Thin Film

A highly efficient white organic light-emitting device (OLED) with a novel sky blue dopant BUBD-1 in a two-color emission system was fabricated. The device achieved an EL efficiency of 17.1 cd/A and 7.9 lm/W at 20 mA/cm2 with CIEx,y coordinates of (x=0.29, y=0.41) which was not changed with drive conditions. The white light OLED reached a half-decay t½ lifetime over 40,000 hours at an initial luminance of 300 cd/m2.

25.3: Highly Efficient White Light Organic Light-Emitting Device

In our recent paper, 1 we presented the study of the emission spectra of triss8-hydroxyquinolined aluminum sAlqd based organic light-emitting diodes sOLEDsd as a function of organic layer thickness. Both calculations and experimental results were presented. The discrepancy between the calculated and measured emission spectra was noted, and possible reasons were discussed. Finally, it was concluded that further study is needed to conclusively establish whether any other phenomena in addition to simple interference play a role in the obtained results. In his recent comment, 2 Shore claimed that our experimental data can be entirely explained by simple interference phenomena, and presented calculations which qualitatively “reproduce” basic behavior of our devices. However, the calculations in our work fFig. 1sbdg also show similar behavior as those presented in the comment by Shore sFig. 2d. Since Shore 2 changed only the Alq layer thickness, while we considered devices with different N, N8-disnaphthalene-1-yl d-N,N8-diphenylbenzidinesNPBd and Alq thicknesses, direct comparison can only be made for the device with 65 nm NPB and 139 nm Alq. It is obvious from Fig. 1sbd in our letter and Fig. 2 in the recent comment 2 that both calculations show essentially the same features. Yet, quantitative agreement between the experimental data and the calculated results is lacking. Since the thicknesses of organic layers were verified by step profiler and spectroscopic ellipsometry after deposition, thickness errors in the fabricated devices are unlikely. Another possible reason for the discrepancy, as correctly identified by Shore, 2 is different emission region thickness. Figure 1 illustrates the influence of the assumed emission region thickness on the calculated electroluminescence sELd spectra. Further studies with confined emitting layers of known thickness are in progress to experimentally establish the influence of the emitting layer thickness. We would also like to point out that, regardless of the assumed emission layer thickness, the calculated spectra always show two peaks, while some of the experimental spectra showed clear shoulders in addition to two peaks. Comparison between the calculated and the experimental spectra for the 65/153s65 nm NPB and 153 nm Alq d device is shown in Fig. 2sad. It can be observed that the calculated spectrum, exhibiting a two-peak structure, does not describe the experimental spectrum well. The calculation for the same

https://espace.library.uq.edu.au/view/UQ:249061/UQ249061_OA.pdf

Response to “Comment on ‘Change of the emission spectra in organic light-emitting diodes by layer thickness modification’” [Appl. Phys. Lett. 86, 186101 (2005)]

An organic light-emitting device (OLED) with enhanced efficiency by employing an ambipolar material, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as both hole-transport and electron-transport layers has been developed. The efficiency of the device is more than 40% enhanced compared with a control device. Moreover, the operational stability is also greatly improved as it minimizes the formation of all unstable redox species of Alq3+ as well as NPB−.

Kok Wai Cheah

Papers

Luminescence properties of ZnSe films grown by hot wall epitaxy

Carbon-based Nano-thin Film for Enhancing Surface Abrasion Resistance on Sapphire Thin Film

25.3: Highly Efficient White Light Organic Light-Emitting Device

Response to “Comment on ‘Change of the emission spectra in organic light-emitting diodes by layer thickness modification’” [Appl. Phys. Lett. 86, 186101 (2005)]

P‐206: Improved OLEDs with Single Ambipolar Material for Hole‐Transport and Electron‐Transport Layers