Solution‐Grown Chloride Perovskite Crystal of Red Afterglow

We report the growth of a halide‐based double perovskite, Cs2NaxAg1−xInCl6:y%Mn, via a facile hydrothermal reaction at 180 °C. Through a co‐doping strategy of both Na+ and Mn2+, the as‐prepared crystals exhibited a red afterglow featuring a high color purity (ca. 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. We report the growth of a halide‐based double perovskite, Cs2NaxAg1−xInCl6:y%Mn, via a facile hydrothermal reaction at 180 °C. Through a co‐doping strategy of both Na+ and Mn2+, the as‐prepared crystals exhibited a red afterglow featuring a high color purity (ca. 100 %) and a long duration time (>5400 s), three orders of magnitude longer than those solution‐processed organic afterglow crystals.