To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

Luminescent materials (or phosphors) are generally characterized by the emission of light with energy beyond thermal equilibrium. More vividly this means: The nature of luminescence is different from that of black-body radiation. Luminescence can occur as a result of many different kinds of excitation, which is reflected in expressions such as photo-, electro-, chemi-, thermo-, sono-, or triboluminescence. In practice, most often the excitation is via X-rays, cathode rays, or UV emission of a gas discharge. The role of the phosphor is to convert the incoming radiation into visible light. In addition to the type of excitation, two other terms are used quite often to classify luminescent materials. Both can be related to the decay time (s): fluorescence (s < 10 ms) and phosphorescence (s > 0.1 s). [1] The luminescence of inorganic solids, which is the focus of this contribution, can be traced to two mechanisms: luminescence of localized centers and luminescence of semiconductors (Fig. 1). [1,2] The first case is represented by transitions between energy levels of single ions (e.g., f±f transitions of Eu 3+ in Y 2 O 3 :Eu 3+ ) or complex ions (e.g., the charge-transfer transition on [WO 4 ] 2± in CaWO 4 ). In the case of luminescent centers, the transition rate is (more or less strongly) correlated to the relevant quantum-mechanical selection rules, and reflected in the intensity as well as the decay time of the transition. Excitation and emission can be (as shown in Fig. 1) both localized to one center (e.g., [WO 4 ] 2± in CaWO 4 ) or separated from each other: excitation on sensitizer (e.g., Ce 3+ in LaPO 4 :Ce 3+ ,Tb 3+ ) is followed by emission on activator (e.g., Tb 3+ in LaPO 4 :Ce 3+

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The development and demonstration of a highly efficient warm‐white all‐nitride phosphor‐converted light emitting diode (pc‐LED) is presented utilizing a GaN based quantum well blue LED and two novel nitrogen containing luminescent materials, both of which are doped with Eu2+. For color conversion of the primary blue the nitridosilicates M2Si5N8 (orange‐red) and MSi2O2N2 (yellow‐green), with M = alkaline earth, were employed, thus achieving a high luminous efficiency (25 lumen/W at 1 W input), excellent color quality (correlated color temperature CCT = 3200 K, general color rendering index Ra > 90) and the highest proven color stability of any pc‐LED obtained so far. Thus, these novel all‐nitride LEDs are superior to both incandescent and fluorescent lamps and may therefore become the next generation of general lighting sources. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

π–π interactions in a phenothiazine-based organic redox polymer lead to an ultra-high cycling stability of a lithium–organic battery.