Tunable Optical Properties, Enhanced Photoluminescence, and Thermostability of CaO: Eu^2+/3+ Phosphors by Codoping Cl^– Ions

Europium-activated calcium oxide (CaO: Eu) phosphor shows great potential in the fabrication of light-emitting diodes (LEDs). However, its luminescent intensity and thermostability still need to be further enhanced. In this work, the photoluminescence property and thermostability of CaO: Eu^2+/3+ were improved significantly by codoping a few of Cl^- ions into it. Compared with CaO: Eu^2+/3+ samples, CaO: Eu^2+/3+, Cl^- phosphors not only have tunable luminescence but also show stronger luminescence intensity and thermal stability. The emission color of phosphors can be tuned by changing the excitation wavelength; typically, strong red/blue light can be displayed under 250/362 nm excitation. More importantly, both the red and blue emissions will increase simultaneously with increasing codoped Cl^- content. When the Cl^- ion content is 0.06, the emission intensity of CaO: 0.01Eu^2+/3+, 0.06Cl^- reaches its maximum and its red and blue emission intensities increase by approximate 2.5 times and 13.2 times, respectively. The results show that CaO: Eu^2+/3+, Cl^- phosphors have potential application value in LEDs and anti-counterfeiting.