Abstract

Blue-emitting phosphors for near ultraviolet (NUV) based tri-color RGB phosphor blend converted white light emitting diodes (LEDs) have been extensively investigated in the past few years. LED chip peaked near 400 nm is the most efficient among the NUV chips currently. However, most of blue phosphors show inefficient excitation around 400 nm. Herein, a novel blue phosphor SrLu2O4:Ce3+ matching well with near 400 nm chip and showing high thermal stability has been developed. The photoluminescence spectrum presents a broad emission band peaking at 460 nm with a bandwidth of nearly 90 nm. By optimizing the Ce3+ concentration, an internal quantum efficiency (IQE) as high as 76% was achieved. Furthermore, 86% of the room-temperature emission intensity is still maintained at 150 °C, indicating a good thermal stability and practicality. A series of white LEDs were fabricated based on 405 nm chips coated with a blend of the new blue phosphor with the commercial yellow and red phosphors. High color rendering indexes (≥90) were achieved while the correlated color temperature was tuneable in the range of 3094 to 8990 K. These results suggest that SrLu2O4:Ce3+ can be utilized as a blue-emitting phosphor in NUV based white LEDs.

Highlights

  • White light emitting diodes (LEDs) have been widely deployed commercially on solid-state lighting, because of their superior efficiency and long life[1]

  • We report to our knowledge for the first time, a novel blue phosphor of SrLu2O4: Ce3+ prepared by solid state reaction

  • White LEDs with high color rendering index (CRI) at different correlated color temperature (CCT) were fabricated based on near ultraviolet (NUV) chips coated with blends of the new blue phosphor with the commercial yellow and red phosphors

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Summary

Introduction

White LEDs have been widely deployed commercially on solid-state lighting, because of their superior efficiency and long life[1]. The inconsistency of the aging characteristics of the blue chip and the phosphor can lead to the instability of the white light which is generated by the combination of the blue light from the chip and the yellow light from the phosphor This type of white LED emits little red light and has a low color rendering index[3,4,5,6,7,8]. To resolve this problem, one can use an alternative method to obtain stable white light by a combination of a red-green-blue (RGB) phosphor blend with a near ultraviolet (NUV) LED chip[9,10]. White LEDs with high color rendering index (CRI) at different correlated color temperature (CCT) were fabricated based on NUV chips coated with blends of the new blue phosphor with the commercial yellow and red phosphors

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