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

A. T. Wieg,J. E. Garay,C. L. Hardin,E. H. Penilla,Y. Kodera

doi:10.1063/1.4971846

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.

Highlights

Broadband white light emission from Ce:Aluminum nitride (AlN) ceramics: High thermal conductivity down-converters for light emitting diodes (LEDs) and laser-driven solid state lighting
Because LEDs are extremely sensitive to temperature fluctuations, thermal management continues to be at the forefront of research and development of white light producing LEDs with most of the work devoted to the design of heat sinks and packaging
In previous investigations using a different RE dopant, we demonstrated that both milling and dopant source can affect RE incorporation in AlN.[10,18]

Summary

Introduction

Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting. Further advantages such as excellent thermal shock resistance[10] and large band gap, 6.2 eV,[11] increase the attractiveness of an AlN-based ceramic down-conversion material for LED based white light.

Results

Conclusion