Far-red-emitting Mn4+-doped Ca2GdZr2Al3O12 phosphors for growing indoor plants

Pc-LEDs (phosphor-converted light-emitting diodes) are a relatively new generation of light sources frequently used for room lighting, backlighting, and plant development on account of numerous advantages, such as compactness, good stability, low energy consumption, and environmental friendliness. However, the absence of red-light emission limits the practical application of pc-LEDs. For example, pc-LEDs have a high correlated color temperature and a low rendering index. Here, a group of far-red emitting Mn4+-doped Ca2GdZr2Al3O12 (CGZA: Mn4+) phosphors was effectively synthesized using a solid-state reaction technique at 1450 °C. The phase purity, morphology, and fluorescence properties of prepared phosphors were investigated using XRD, SEM, PL/PLE, and fluorescence decay analysis, respectively. Under a 344-nm excitation, CGZA: Mn4+ emitted high-purity far-red light with a peak at approximately 702 nm. Phosphor quenching was observed once the Mn4+ concentration reached 0.3 mol%. The concentration quenching mechanism of Mn4+in the CGZA matrix resulted from electric dipole-dipole interactions. An important result was that the PL band was well superposed on the absorption bands of phytochromes Pr and Pfr. The PL intensity was 50% of the initial value at 373 K. These experimental results demonstrated the board application potential of the prepared phosphors for plant breeding.