Study on the mechanism of high energy transfer efficiency of blue light excited Cr, Nd co-doped near infrared phosphors.

Although Cr as activator for Near infrared (NIR) phosphors has been widely studied, the peaks of Cr emission spectra in most hosts are less than 1000 nm. Nd as an activator in many hosts has a wide distribution of absorption peaks in the Ultraviolet-visible-Near infrared (UV-vis-NIR) band, especially in the 650-900 nm band for effective NIR to NIR Stokes luminescence (F→I, F→I transitions). Therefore, Cr, Nd co-doping to achieve the emission in the NIR II region (1000-1700nm) is very meaningful. Here, we report LaCaZrO(LCZO): Cr, Nd NIR phosphors with emission spectra covering an ultra-wide range of 700-1400 nm and reveal their luminescence mechanism. The energy transfer efficiency of Cr for Nd can be as high as 88.4% under 471 nm blue light excitation. In the same case, the integrated intensity of the emission spectra of Cr, Nd co-doped can reach 847% of that of Nd alone and 204% of that of Cr alone. Finally, the combination of commercial blue light chips and Cr, Nd co-doped NIR phosphors shows great potential for applications in face recognition, night lighting, and angiography.