Exploration of the structural and optical properties of a red-emitting phosphor K2TiF6:Mn4+

The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode (WEED) devices. Transition metal Mn-doped compounds are fascinating luminescent materials. Herein, we performed a systematic theoretical study of the microstructure and optical properties of K2TiF6:Mn4+ using the CALYPSO structure search method in combination with first-principles calculations. We uncovered a novel structure of K2TiF6:Mn4+ with space group P-3m1 symmetry, where the impurity Mn4+ ions are accurately located at the center of the MnF6 octahedra. Based on our developed complete energy matrix diagonalization (CEMD) method, we calculated transition lines for (2)Eg -> (4)A(2), (4)A(2) -> T-4(2), and (4)A(2) -> T-4(2) at 642 nm, 471 nm, and 352 nm, respectively, which are in good agreement with the available experimental data. More remarkably, we also found another transition ((4)A(2) -> T-2(2)) that lies at 380 nm, which should be a promising candidate for laser action.