Simultaneous improvement in emission intensity and spectral purity of red photon upconversion in Gd2O3:Yb3+/Er3+ phosphors under 1550 nm excitation

Upconversion luminescent nano-materials with both excitation and emission peaks in the “optical window” is of significant importance for application in deeper bio-imaging, due to the weak effects of light absorption, light scattering, and auto-fluorescence. This paper reports an Er3+ self-sensitized red up-converting nanophosphors with improved emission intensity and spectral purity. The influence of Yb3+ concentration on upconversion luminescence properties is investigated comprehensively. Compared with the sample without Yb3+ doping, the luminescence intensity in the sample with 10% Yb3+ is increased by 12.9 times. Moreover, the dominant wavelength at 1550 nm excitation is about 60 nm larger than that excited at 980 nm. It has been demonstrated that Yb3+ co-doping can not only improve the photon absorption at 1550 nm and the probability of red emission, but also suppress other light emissions and phonon emission through the selective population of red-emitting level.