Highly efficient all‐nitride phosphor‐converted white light emitting diode

Abstract

In the Editor's Choice [1] 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 doped with Eu2+. These novel LEDs are superior to both incandescent and fluorescent lamps and may therefore become the next generation of general lighting sources. The cover picture is an artist's view of the 2‐pc‐LED: On a copper slug and underneath a plastic lens a ‘flip‐chip’ is soldered to metal contacts; ‘flip‐chip’ meaning the substrate on which the stack of GaN and InGaN layers has been deposited is used as light exit, the (bottom) p‐contacts being highly reflective. The color converting phosphors are placed on top of the chip, embedded in silicone. Primary blue as well as color‐converted red and green photons are emitted. The first author, Regina Mueller‐Mach, manages the Charac‐terization Laboratory at Lumileds which runs R&D work on phosphor converted LEDs in close cooperation with Philips Research Laboratories and the Department of Chemistry and Biochemistry of the University of Munich.

Luminescence properties of SrSi2O2N2 doped with divalent rare earth ions

“…The luminescence characteristics of the Eu 2+ -doped SrSi 2 O 2 N 2 are shown to be very promising for application in pcLEDs. This is substantiated by a recent paper on an all-nitride, phosphor-converted white light emitting diode using the Eu 2+ -doped title compound [13].…”

“…The absence of luminescence quenching below 500 K in combination with the high luminescence quantum yield (90% for SrSi 2 O 2 N 2 :Eu 2+ 2%) implies that this material is very promising for application as a luminescence converter in phosphor-converted LEDs [13].…”

Research challenges to ultra‐efficient inorganic solid‐state lighting

“…Oxonitridosilicates, M II Si 2 O 2 N 2 (M = Ca, Sr), have been identified more recently as a promising new class of phosphors with strong blue absorption, high quantum efficiency and excellent thermal stability [57,60,89]. Green emission from SrSi 2 O 2 N 2 :Eu 2+ (FWHM = 78 nm, λ max = 538 nm) has been reported to exhibit quantum efficiencies >90%, even at temperatures above 200…”

“…In these M 2 Si 5 N 8 host lattices (as in the M II M III 2 S 4 family discussed in connection with the wideband green phosphor), Eu 2+ emission is sensitive to the size of the cations and can be tuned from yellow to deep red by varying the occupancy of the M site (M = Eu, Ba, Sr, Ca) [57]. For example, Sr 2 Si 5 N 8 :Eu 2+ emits in the red [57] and, importantly, its quantum efficiency does not appear to decrease significantly at operating temperatures of 125…”

“…• C [57]. The recently developed red-emitting phosphor (Sr,Ca)AlSiN 3 appears to have great promise for SSL, though its synthesis is difficult, and its emission is broader than optimal.…”