Upconversion white-light emission in Ho3+/Yb3+/Tm3+ codoped LiNbO3 polycrystals

Ho3+/Yb3+/Tm3+ codoped LiNbO3 polycrystals exhibiting upconversion white-light under 980 nm excitation have been successfully fabricated by the high temperature solid-state reaction method. CIE coordinate of the Ho3+/Yb3+/Tm3+/LiNbO3 polycrystal is (0.34, 0.35), which is very close to the standard equal energy white-light illuminate (0.33, 0.33). Efficient green, red, and blue upconversion emissions have been observed. The luminescent decay dynamics are studied, and rate equations for the blue, green, and red emissions are set up to analyze the upconversion luminescence mechanism. The present results demonstrate that the competition between the linear decay and the upconversion process for the depletion of the intermediate excited states plays an important role in upconversion mechanism. The LiNbO3 with upconversion white-light will be a promising luminous material.