Near-Infrared Afterglow and Related Photochromism from Solution-Grown Perovskite Crystal

Near-infrared (NIR) afterglow is keenly sought in emerging areas including deep-tissue imaging and night-vision surveillance, while only few successes in powder phosphors are achieved through solid-state calcination. In this work, a perovskite single crystal, namely Cs2Na0.2Ag0.8InCl6:Yb3+, is grown in solution via a simple hydrothermal reaction. Through a co-doping strategy involving both Na+ and Yb3+, dual-band emission in the visible and NIR region is activated by self-trapped excitons (STE) and lanthanide ions, respectively. Importantly, the total photoluminescence quantum yield (PL QY) of both bands is boosted to approximate to 82%. Intriguingly, a long-lasting afterglow at the NIR band (approximate to 7200 s) and a simultaneous photochromism is observed after ceasing the excitation. Importantly, the transparency of crystals exhibit a pronounced contrast in the decoloration process, enabling a quantitative analysis of photochromism at varied temperatures. On the other hand, the transparent crystals enable the design of a light-storage battery free of reabsorption, featuring a linear power output with crystal loading. This work proposes a new paradigm to quantitatively correlate the afterglow traps to photochromism, opening many possibilities to practical applications of NIR-afterglow transparent crystals.