Effect of defect state on photon synergistic process in KLu2F7:Yb3+, Er3+ nanoparticles

The synergistic effect appeared due to the cooperative dual-wavelength excitation by near-infrared (NIR) and ultraviolet (UV) light in rare-earth doped nano-particles (NPs) is very important to improve solar cell efficiency. Herein, we studied the synergistic effect combined with the energy levels of Er 3+ ions and the defect states in KLu 2 F 7 NPs. The introduction of Ce 3+ ions in KLu 2 F 7 :16%Yb 3+ , 2%Er 3+ NPs results in significant improvement of synergistic effect by producing more vacancy defects ( V K ′ $V_K^{\prime }$ ) which serves as shallow traps. We verify unambiguously that the control of the defects distribution exerts a facile approach to promote the synergistic effect with the assistance of Ce 3+ ions doping.