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

► CIE coordinate of the Ho3+/Yb3+/Tm3+/LiNbO3 is (0.34, 0.35). ► Efficient red, green, and blue emissions are observed. ► Competition (Linear and UC) involved in upconversion process. ► The ET from Tm3+ to Ho3+ is observed.