Upconversion emission enhancement in Er3+/Yb3+-codoped BaTiO3 nanocrystals by tridoping with Li+ ions

► Er3+/Yb3+-codoped BaTiO3 nanocrystals emit green and red upconversion luminescence. ► Increasing Yb3+ content increases red upconversion luminescence. ► Increasing Li+ content increases green and red upconversion luminescence.