TY - JOUR
T1 - Enhanced quantum efficiency of a self-organized silica mixed red phosphor CaAlSiN3:Eu
AU - Oishi, Masatsugu
AU - Shiomi, Shohei
AU - Ohara, Koji
AU - Fujishiro, Fumito
AU - Kai, Yoichiro
AU - Shih, Shao Ju
AU - Moriga, Toshihiro
AU - Chichibu, Shigefusa F.
AU - Takatori, Aiko
AU - Kojima, Kazunobu
N1 - Funding Information:
We thank Dr. Kenichiro Ikemura, Hamamatsu Photonics for the QE and fluorescence lifetime experiments. We thank Dr. Toshiaki Ina, Japan Synchrotron Radiation Research Institute, for the support during the XAFS experiments. We are also grateful to Mr. Tomoyuki Ueki and Masashi Maeda, Tokushima University, for the TEM and PL measurments. The authors are grateful to Ms. Natsumi Hirayama, Tokushima University, for the diffuse reflectance measurement. The XAFS and high-energy X-ray total scattering experiments were perfomed at SPring-8 under proposals 2017B1307, 2017A1347, and 2017B1437. This work was performed under the Research Program of Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials in Network Joint Research Center for Materials and Devices, and Collaboration Program by and between Tokushima University (TU) and National Taiwan University of Science and Technology (NTUST).
Publisher Copyright:
© 2022 Elsevier Inc.
PY - 2022/5
Y1 - 2022/5
N2 - This study develops self-organized silica mixed CaAlSiN3:Eu (CASN) powder which improves light extraction efficiency (LEE) of the phosphor particles by enhanced scattering. A simple powder process conducted at room temperature, which is free from high temperature sintering process often applied for glass coated phosphors. Red phosphor CASN particles with a size of a few microns are mixed with nano-sized silica which was prepared in a tetraethyl orthosilicate (TEOS) solution of an alkali hydrolysis bath. The pair distribution function (PDF) profile obtained by an X-ray total scattering experiment indicates that the obtained nano-sized silica powders were amorphous. Compared to pure CASN powders, the composite CASN has an increased diffuse reflection, a reduced amount of absorption light, and an improved quantum efficiency (QE) of about 15%. QE is the product of internal quantum efficiency (IQE) and light extraction efficiency (LEE). The light emission lifetime measurement does not show a noticeable change between the pure and composite samples, indicating that the mixing process does not affect the electronic state of the Eu2+ luminescence center of CASN powder. That is, IQE of composite CASN is the same with that of pure CASN particles. Therefore, the improvement of QE of the composite CASN powders is due to the improvement of LEE.
AB - This study develops self-organized silica mixed CaAlSiN3:Eu (CASN) powder which improves light extraction efficiency (LEE) of the phosphor particles by enhanced scattering. A simple powder process conducted at room temperature, which is free from high temperature sintering process often applied for glass coated phosphors. Red phosphor CASN particles with a size of a few microns are mixed with nano-sized silica which was prepared in a tetraethyl orthosilicate (TEOS) solution of an alkali hydrolysis bath. The pair distribution function (PDF) profile obtained by an X-ray total scattering experiment indicates that the obtained nano-sized silica powders were amorphous. Compared to pure CASN powders, the composite CASN has an increased diffuse reflection, a reduced amount of absorption light, and an improved quantum efficiency (QE) of about 15%. QE is the product of internal quantum efficiency (IQE) and light extraction efficiency (LEE). The light emission lifetime measurement does not show a noticeable change between the pure and composite samples, indicating that the mixing process does not affect the electronic state of the Eu2+ luminescence center of CASN powder. That is, IQE of composite CASN is the same with that of pure CASN particles. Therefore, the improvement of QE of the composite CASN powders is due to the improvement of LEE.
KW - (Oxy)nitride phosphors
KW - Amorphous silica mixture
KW - Composites
KW - Photoluminescence
KW - Quantum efficiency
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U2 - 10.1016/j.jssc.2022.122968
DO - 10.1016/j.jssc.2022.122968
M3 - Article
AN - SCOPUS:85124218712
SN - 0022-4596
VL - 309
JO - Journal of Solid State Chemistry
JF - Journal of Solid State Chemistry
M1 - 122968
ER -