No abstract

Solid-state light sources are in the process of profoundly changing the way humans generate light for general lighting applications. Solid-state light sources possess two highly desirable features, which set them apart from most other light sources: (i) they have the potential to create light with essentially unit power efficiency and (ii) the properties of light, such as spectral composition and temporal modulation, can be controlled to a degree that is not possible with conventional light sources such as incandescent and fluorescent lamps. The implications are enormous and, as a consequence, many positive developments are to be expected including a reduction in global energy consumption, reduction of global-warming-gas and pollutant emissions and a multitude of new functionalities benefiting numerous applications. This review will assess the impact of solid-state lighting technology on energy consumption, the environment and on emerging application fields that make use of the controllability afforded by solid-state sources. The review will also discuss technical areas that fuel continued progress in solid-state lighting. Specifically, we will review the use of novel phosphor distributions in white light-emitting diodes (LEDs) and show the strong influence of phosphor distribution on efficiency. We will also review the use of reflectors in LEDs with emphasis on 'perfect' reflectors, i.e. reflectors with highly reflective omni-directional characteristics. Finally, we will discuss a new class of thin-film materials with an unprecedented low refractive index. Such low-n materials may strongly contribute to the continuous progress in solid-state lighting.

The sesquiterpene (E)-β-farnesene (EBF) is the alarm pheromone for many species of aphids [1]. When released from aphids attacked by parasitoids or predators, it alerts nearby conspecifics to escape by walking away and dropping off the host plant [2, 3]. The reception of alarm pheromone in aphids is accomplished through a highly sensitive chemosensory system. Although olfaction-related gene families including odorant receptors (ORs) and odorant-binding proteins (OBPs) have recently been identified from aphid genomes [4-6], the cellular and molecular mechanisms of EBF reception are still largely unknown. Here we demonstrate that ApisOR5, a member of the large superfamily of odorant receptors, is expressed in large placoid sensillum neurons on the sixth antennal segment and confers response to EBF when co-expressed with Orco, an obligate odorant receptor co-receptor, in parallel heterologous expression systems. In addition, the repellent behavior of Acyrthosiphon pisum to EBF disappears after knocking down ApisOR5 by RNAi as well as two A. pisum odorant-binding proteins known to bind EBF (ApisOBP3 and ApisOBP7). Furthermore, other odorants that can also activate ApisOR5, such as geranyl acetate, significantly repel A. pisum, as does EBF. Taken together, these data allow us to conclude that ApisOR5 is essential to EBF reception in A. pisum. The characterization of the EBF receptor allows high-throughput screening of aphid repellents, providing the necessary information to develop new strategies for aphid control.

Assuming large color gamut and therefore better color reproducibility will be a highly desired feature of all displays as we look to the near future, we make the case in this paper that Quantum Dots (QDs) are currently the down-conversion technology of choice that will allow liquid crystal display (LCD) makers to cost-effectively reach and exceed 100% of the NTSC (National Television Standard Committee) standard while achieving maximum system efficiency. We will discuss in detail the numerous fundamental advantages of QDs over phosphors, along with their scientific origins, and make the case that QDs are the ultimate light generating material for next-generation displays. OBJECTIVE AND BACKGROUNDLCD backlights generate light that is transmitted through a color filter array (CFA) in the liquid crystal panel, which together determine the range of colors the display can render and therefore size of the color gamut. By changing the spectral profile of the backlight unit with down-conversion materials, wider color gamuts can be achieved than with the typical yellow phosphor (Ce:YAG) and blue LED system.Recently, several types of red and green emitting phosphors [1] have been re-formulated to have narrower band emission compared to yellow phosphors typically used for white LED LCDs, increasing the color gamut to ~80% coverage of NTSC (~60% coverage of Rec. 2020) at reasonable system efficiencies. While it is possible that narrow-band red and green emitting phosphor technology will continue to improve over the next several years and be applied more heavily to LCD displays, it is a mature technology that may be reaching practical limits. Colloidal semiconductor nanocrystals or quantum dots (QDs), on the other hand, represent a relatively new display technology that is demonstrating significant and fundamental advantages over sulfide and nitride based narrow-band red and green emitting phosphors. In this paper we will discuss recent progress on red and green emitting QD materials for display applications and compare and contrast fundamental emitter properties and future potential with those of red and green phosphors.The exceptional quality of QD materials and the degree of control over their important optical properties at mass production scales have allowed the launch of the first mainstream QD-enhanced consumer electronic products. Sony Bravia Triluminos TVs containing QD Vision's Color IQ TM optics were first announced at the 2013 Consumer Electronics Show with a color gamut of ~100% NTSC (CIE 1931) area. Recently 3M and Nanosys also successfully launched a main stream QD-enhanced display product with the Amazon Kindle Fire HDX 7.9" tablet. Figure 1 shows examples of these two QD-enhanced LCD displays. The benefits of using QDs as the down-conversion material for LCD displays are numerous, and many prominent analysts are now forecasting most wide color gamut LCD displays will be QD-enhanced over the next several years. Figure 2 shows the three primary architectures for incorporation of QDs into an LCD display,...

The junction temperature of AlGaN ultraviolet light-emitting diodes emitting at 295nm is measured by using the temperature coefficients of the diode forward voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-forward voltage is the most accurate (±3°C). A theoretical model for the dependence of the diode forward voltage (Vf) on junction temperature (Tj) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6K∕W is obtained with the device mounted with thermal paste on a heat sink.