Modulating trap distribution of persistent phosphors upon simple microwave-assisted solid-state reactions

The trap distribution due to defects in persistent luminescent materials plays a significant role in their scope of applications. However, it is a big challenge to manipulate or modulate this trap distribution. In this work, the trap distribution of green emitting persistent phosphor Li2ZnGeO4:Mn2+ is modulated upon a facile microwave assisted solid-state reaction. A series of systematic temperature dependent trapping, de-trapping and re-trapping measurements are designed to shed light on trap information. An appealing feature of the present synthesis approach is that the trap distribution is modulated towards shallow traps, which offers great promise in low temperature glow-in-the-dark applications. More importantly, trap re-shuffling can be achieved towards two directions, both lower energy level (shallow traps) and higher energy levels (deep traps) upon light stimulation. These findings indicate there are optically active trapping defects with photo-stimulated re-trapping behavior in this persistent phosphor. This work not only provides a fundamental advance in revealing re-trapping behavior, but also offers a guidance for the modulation of trap distribution in persistent phosphors upon a facile approach.