A high-efficiency double perovskite phosphor SrLaNaTeO6:Mn4+: Potential applications in w-LEDs and indoor plant growth lighting

A novel deep-red phosphor with Mn 4+ -doped double perovskites SrLaNaTeO 6 (SLNTO) was synthesized by the conventional high-temperature solid-state method. SLNTO contains both [NaO 6 ] and [TeO 6 ] octahedra. The octahedral structure of double perovskites facilitates the doping of Mn 4+ . The band gap ( E g ) of the direct semiconductor SLNTO is 2.88 eV. With an excitation wavelength of 322 nm, SLNTO:Mn 4+ has a 700 nm deep-red wavelength emission assigned to the energy level transition from 2 E 1g to 4 A 2g of Mn 4+ ions. Photoluminescence (PL) of the sample and phytochrome far-red light (P FR ) absorption are satisfactory matches. According to the Tanabe-Sugano diagram, Mn 4+ is located in the strong crystalline field for 2 E 1g . A 2.0 mol% concentration of Mn 4+ is optimal; further high doping results in concentration quenching, ascribed to the neighbour ion interaction and dipole‒dipole ( d-d ) interactions. The internal quantum efficiency (IQE) is 87.84 %. Additionally, the electroluminescent (EL) spectrum of the encapsulated plant growth lamp overlaps with the chlorophyll a and b absorption spectra . Its Commission Internationale de l'Eclairage (CIE) coordinates of SLNTO:2.0 mol%Mn 4+ phosphor with a near-ultraviolet (n-UV) chip are located in (0.720, 0.280). The phosphor-converted white light-emitting diode (pc-WLED) has a high colour rendering index ( R a  = 96) with a suitable correlated colour temperature (CCT = 6240 K). The results are satisfactory for white light-emitting diodes (w-LEDs) and plant growth lamps.