Regulating the concentration quenching in Eu3+-activated Lu2W3O12 red-emitting phosphors through phase transition for white light-emitting diode and plant growth applications

Abstract

Red emission is crucial for fabricating high-quality phosphor-converted light emitting-diode (LED) to satisfy its vivid applications. Herein, Lu2(1-x)W3O12:2xEu3+ (Lu2W3O12:2xEu3+) red-emitting phosphors were developed through sol-gel reaction method. Through adding Eu3+, phase transition, from orthorhombic to monoclinic phase, happened in studied samples. Excited at 394 nm, the resulting phosphors emitted intense red emission and their intensities can be manipulated via phase transition. Specifically, the phase transition can delay concentration quenching in resultant phosphors, of which the optimal state was realized at x = 0.7, resulting in enhanced luminescence properties. Besides, the color purity and thermal stability of prepared phosphors can also be improved by means of phase transition. Based on Judd-Ofelt theory, the local symmetric performances of Eu3+ in synthesized phosphors were analyzed via calculating the corresponding Ω2 values. Via using the designed phosphors as red-emitting components, different types of LED devices were packaged, i.e. red-emitting LED and white-LED. For red-emitting LEDs, their emission bands matched well with the absorption bands of plant pigments, allowing their applications in plant growth, which had been confirmed by rice growth experiments. Furthermore, the packaged white-LED can emit warm white light with high color rendering index and low correlated color temperature, which were slightly impacted by working current. Our finding revealed that phase transition was an efficient route to delay the concentration quenching effect and regulate the luminescence characterizations of Eu3+-activated phosphors.