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Light-emitting diodes (LEDs) continue to penetrate the global market; their pervasiveness clearly being felt in such diverse fields as technological, socio-economic and commercial interests. The multi-billion dollar LED market is shared by various segments, including office and household lighting, street lighting, the automobile industry, traffic signals, backlighting for hand-held devices, indoor and outdoor signs and indicators, medicine, communication systems, crop cultivation using artificial light and many more. The technological development of LEDs has undergone many phases in different parts of the world. From the early discovery of luminescence to the invention of highly efficient organic LEDs, researchers have worked with the prime purpose of improving the performance of luminaires. The need to infuse the market with more efficient and cheaper products has been prevalent from the start. LEDs are a result of this uncontrolled desire of researchers to develop superior products that would displace existing products in the market. To understand what led to the current prominence of LEDs, we give a brief historical overview of the field followed by a thorough discussion of the positive features of LEDs. This work includes the basic requirements, advantages and disadvantages of LEDs in a variety of applications. A brief description of the diverse applications of LED in fields such as lighting, indicators and displays, farming, medicine and communication is given. Considerable importance is placed on discussing the possible difficulties that must be overcome before using LEDs in commercial applications.

A series of CaZr4(PO4)6:Dy3+, CaZr4(PO4)6:Ce3+ and CaZr4(PO4)6:Dy3+, Ce3+ phosphors were prepared by the solid state reaction process.

This work reports the theoretical analysis of the electron-vibrational interaction (EVI) in 4f-5d optical transitions of Eu ions in ABaPO (A = Li, Na, K and Rb) systems. The EVI parameters were estimated from the recently reported room temperature photoluminescence results, by employing the spectrum-fitting method. Parameters such as the Huang-Rhys factor, effective phonon energy, Stokes shift and zero-phonon line position were estimated and are reported here. The estimated EVI parameters were validated by modeling the emission band and establishing the agreement between the experimental and modeled emission bands. Copyright © 2016 John Wiley & Sons, Ltd.

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