Dual-mode luminescence: a new perspective in calcium molybdate phosphor for solar cell application

Herein, a dual mode luminescence behavior of rare earth doped/codoped CaMoO₄:(Eu³⁺, Eu³⁺/Yb³⁺) phosphors synthesized by hydrothermal method are presented. The structural analysis and surface morphology were investigated by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The optical properties were studied through UV–vis diffuse reflectance spectroscopy, photoluminescence (PL) and lifetime measurements. The PL excitation spectra of Eu³⁺ doped CaMoO₄ phosphors were recorded at different excitation wavelengths such as 250, 270, 300, 394 nm wavelengths. The down-shifting PL emission spectra of phosphors were recorded at optimized 250 nm excitation wavelength. In addition, emission was also recorded for Eu³⁺/Yb³⁺ codoped CaMoO₄ phosphor after an excitation wavelength 980 nm through up-conversion process. The phosphors show hypersensitive red emission (⁵D₀ → ⁷F₂) through down-shifting as well as up-conversion processes. The red color was visualized by using commission international de L’Eclairage (CIE) chromaticity diagram. Thus, the obtained results show that dual-mode red emitting phosphors may be used as spectral converter in solar cells.