Research on the Preparation and Luminescent Properties of Ca0.87-xSrxAl2Si2O8:0.13Eu2+ Broad Band Blue Phosphor for White Light LEDs

TL;DR

This study develops a new broadband blue phosphor Ca0.87-xSrxAl2Si2O8:0.13Eu2+ with enhanced luminescent properties for white LEDs, achieving high quantum efficiency, stable emission at elevated temperatures, and excellent color rendering.

Contribution

It introduces a cation substitution strategy to optimize a feldspar-structured phosphor with improved luminescence and thermal stability for LED applications.

Findings

Luminescence intensity doubled with optimal Sr2+ concentration.

Internal quantum efficiency reached 84.1%.

White LED with high color rendering index of 94.3% was fabricated.

Abstract

White light emitting diodes (LEDs) have become the most widely used lighting devices due to their high luminous efficiency, environmental friendliness, long lifespan, and energy-saving advantages. Currently, the production of white light LEDs faces challenges such as a lack of cyan light emission, which results in a low color rendering index (Ra), as well as issues related to poor thermal stability of the luminescent materials and difficulties in synthesis. This paper employs a high-temperature solid-state method and cation substitution strategy to prepare a broadband blue phosphor Ca0.87-xSrxAl2Si2O8: 0.13Eu2+ (x=0-0.87) with a feldspar structure. By varying the concentration of x, phase transitions are achieved, leading to the formation of two luminescent centers. The luminescence intensity of Ca0.87Al2Si2O8:0.13Eu2+ is enhanced by 2 times, and the internal quantum efficiency (IQE) increases by 24.8%. The internal quantum efficiency of Ca0.27Sr0.60Al2Si2O8:0.13Eu2+ reaches as high as 84.1%. The strongest emission peak is observed when the concentration of Sr2+ reaches 0.6 mol, with a full width at half maximum of 91 nm. The experimental value of the optical band gap of the matrix is 5.74 eV, indicating that the luminescence intensity of the sample Ca0.27Sr0.60Al2Si2O8:0.13Eu2+ at 150{\deg}C is 92.2% of that at room temperature. Ca0.27Sr0.60Al2Si2O8:0.13Eu2+ and commercial red phosphor (Ca,Sr)AlSiN3:Eu2+, as well as commercial green phosphor (Sr,Ba)2SiO4:Eu2+, have been successfully packaged into white light LED devices using a 365nm near-ultraviolet chip. The color rendering index (Ra) of this white light LED device is 94.3, with a color coordinate of (0.4094, 0.4167) and a correlated color temperature (CCT) of 3611.4K.