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LEDs are in the midst of revolutionizing the lighting industry Up-to-date and comprehensive coverage of light-emitting materials and devices used in solid state lighting and displays Presents the fundamental principles underlying luminescence Includes inorganic and organic materials and devices LEDs offer high efficiency, long life and mercury free lighting solutions

ZnO nanowires have been grown on polycrystalline Zn 2 GeO 4 :Mn substrates for the first time using a chemical vapor deposition method. Both Zn and ZnO sources were used to supply Zn vapor in the growth process of ZnO nanowires. The Zn 2 GeO 4 :Mn substrates were prepared using solid-state ceramic synthesis methods, and average grain sizes of ~1 μm were achieved. The nanowires of diameters in the range of 100–200 nm and length of ~30 μm were observed. In addition to nanowires, other morphologies of ZnO nanostructures, such as ZnO tetrapods, were observed when Zn powder was used as the source for the CVD growth. The results reveal that polycrystalline substrates are also promising as novel alternative substrates for growth of ZnO nanostructures. The as-synthesized ZnO nanowire/Zn 2 GeO 4 :Mn composites are being developed for future electroluminescent devices.

The influence of microindentation on the electroluminescence of silicon carbide was studied in forward-biased 4H SiC p-i-n junctions. Four spectral regions at approximately 390, 420, 445 and 500 nm initially observed on virgin samples strongly depend, in regard to magnitude, on the condition of the starting die. These spectral regions may be interpreted as arising from either phonon-assisted band-to-band transitions or from defect-related transitions. The same SiC die were then subjected to mechanical damage brought about by a series of closely spaced microindentations directed approximately perpendicular to the c-axis. The spectra taken after a first set and subsequently a second set of microindentations are distinct from the initial spectra in all cases, and differences are interpreted as being due to the modification of existing defects or additional defects being generated mechanically. The influence of microindentation on the ideality factor is measured and discussed. Measured light flux with respect to a standard light source is also shown at each microindentation stage.

ZnO nanowires have been grown on polycrystalline Zn.sub.2GeO.sub.4:Mn substrates for the first time using a chemical vapor deposition method. Both Zn and ZnO sources were used to supply Zn vapor in the growth process of ZnO nanowires. The Zn.sub.2GeO.sub.4:Mn substrates were prepared using solid-state ceramic synthesis methods, and average grain sizes of ~1 [mu]m were achieved. The nanowires of diameters in the range of 100-200 nm and length of ~30 [mu]m were observed. In addition to nanowires, other morphologies of ZnO nanostructures, such as ZnO tetrapods, were observed when Zn powder was used as the source for the CVD growth. The results reveal that polycrystalline substrates are also promising as novel alternative substrates for growth of ZnO nanostructures. The as-synthesized ZnO nanowire/Zn.sub.2GeO.sub.4:Mn composites are being developed for future electroluminescent devices.

Earth‐abundant, fluorescent silicon carbide (SiC) quantum dots (QDs) have recently attracted remarkable attention on account of their long‐term chemical and optical stability and impressive biocompatibility. However, there has been a long‐standing debate among researchers concerning whether radiative recombination in SiC QDs is governed by quantum confinement effects or by surface‐related states. Herein, the underlying mechanism responsible for the photoluminescence observed in SiC QDs is elucidated. Significant progress made through the development of advanced strategies for synthesizing ultrasmall SiC QDs and modifying their surfaces with functional groups, conjugated molecules, and protective shells is discussed. Subsequently, the potential for engineered SiC QDs to be applied to a range of sectors, including energy (photocatalytic‐based CO2 reduction systems), electronics/optoelectronics (electroluminescent white light‐emitting diodes, nonlinear optics, and quantum sensing), and biomedicine (cell imaging and biosensors), is reviewed. Finally, this review is summarized with some forward‐looking challenges and prospects. Fluorescent silicon carbide quantum dots with excellent biocompatibility and chemical stability are gaining increasing attention. This review resolves the long‐standing debate on their emission origin, demonstrating the dominant role of surface states in radiative recombination. It further highlights recent progress in synthesis strategies, surface engineering for enhanced photoluminescence quantum yield, and applications in energy, biosensing/bioimaging, and optoelectronics.

Alternating current (AC) electroluminescent light emitting materials and devices play a small but continuing role in today's solid state lighting and display markets. The semiconductor‐based solid state conversion of electrical energy to visible light has become dominated by both inorganic and organic p‐n junction light emitting diode (LED) devices, however there are other mechanisms of effecting luminescence from electron‐hole pair recombination in devices that do not necessarily have both p‐type and n‐type regions. In contrast to organic light emitting diode (OLED) devices, powder electroluminescence (EL) and thin film electroluminescence (TFEL) materials are relatively air and moisture insensitive due to their use of inorganic crystalline materials. The use of free‐standing and self‐supporting ceramic sheets for EL substrates has been employed to develop a number of new EL phosphors. The device structure is effectively composed of numerous spherical, small‐area TFEL devices embedded within a polymer film.

This chapter presents a series of more specific luminescence processes. It discusses the physics required to understand excitons and optical processes in molecular materials. The molecular exciton is fundamental to organic light emitting diode (OLED) operation. It is possible for the molecule to be excited to form an exciton by electrical means rather than by the absorption of a photon which is the situation in OLEDs. The most important applications of LEDs and OLEDs are for visible illumination and displays. This requires the use of units to measure the brightness and color of light output. To determine the probability of occupancy of states in the bands, people use Fermi‐Dirac statistics. The chapter introduces photometric units and relates them to radiometric units. Finally, it summarizes the key concepts underlying p‐n junction operation for reference and detailed quantitative treatments.