Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

Abstract

We introduce high thermal conductivity aluminum nitride (AlN) as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL) emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l’Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

“…successfully incorporated Tb 3+ into the Al 2 O 3 matrix with a concentration as high as 0.5 at% . Similarly, AlN:Ce phosphor ceramic was successfully prepared with the CAPAD procedure . The thermal conductivity of the sintered AlN:Ce ceramic is expected to be >90 W m −1 K −1 .…”

“…h–j) Photographs of the white light emission by coupling AlN:Ce ceramics to the 355 nm laser source. Reproduced with permission . Copyright 2016, American Institute of Physics.…”

A Thermally Robust La3Si6N11:Ce‐in‐Glass Film for High‐Brightness Blue‐Laser‐Driven Solid State Lighting

“…Wieg et al. prepared a white‐emitting AlN:Ce ceramic with a high thermal conductivity, which is suitable for UV laser–driven high‐power lighting . Despite these efforts, most nitride phosphors can hardly be sintered to dense ceramics with acceptable optical properties due to their intrinsic low diffusion rate .…”

Extremely Slow Decay of Yellow Luminescence in Be‐Doped GaN and Its Identification

“…Very interesting for applications are LEDs emitting white light. Today, these LEDs are mostly obtained using phosphors to convert blue or ultra‐violet light into white light . Teisseyre et al used a Be‐doped GaN crystal as optical converter for a blue emitting LED.…”