Solution‐Grown Chloride Perovskite Crystal of Red Afterglow

Oxide-based afterglow materials were usually produced through high-temperature treatment (> 1000 °C), which brought both considerable energy consumption and safety risk to manufacturer. Here, we report the growth of a halide-based double perovskite, Cs 2 Na x Ag 1-x InCl 6 :y%Mn, via a facile hydrothermal reaction at 180 °C. Through a co-doping strategy of both Na + and Mn 2+ , the as-prepared crystals exhibited a red afterglow featuring a high color purity (~ 100%) and a long duration time (> 5400 s), three orders of magnitude longer than those solution-processed organic afterglow crystals. The energy transfer (ET) process between self-trapped excitons (STE) and activators was investigated through time-resolved spectroscopy, which suggested an ET efficiency up to 41%. Importantly, the nominal concentration of dopants, especially in the case of Na + , was found a useful tool to control both energy level and number distribution of traps. Cryogenic afterglow measurements suggested that the afterglow phenomenon was likely governed by thermal-activated exciton diffusion and electron tunneling process. Our work provided a convenient access to a new class of afterglow materials with low lattice energy, representing a paradigm for low-temperature synthesis of afterglow crystals.