Strong Self-Trapped Exciton Emission and Highly Efficient Near-Infrared luminescence in Sb3+-Yb3+ Co-doped Cs2AgInCl6 Double Perovskite

Yb3+ doped lead-free double perovskites (DPs) with near-infrared (NIR)-emitting have attracted extensive attention due to their wide application prospects. Unfortunately, they still suffer from weak NIR emission due to undesirable resonance energy transfer between the sensitizers and Yb3+ ions. Herein, a new effective NIR-emitting DP is developed by co-doping Sb3+ and Yb3+ into Cs2AgInCl6. Experiments and theoretical calculations reveal that induced by co-doping Sb3+ ions, the self-trapped excitation (STE) emission intensity of Cs2AgInCl6 is greatly enhanced by 240 times, and the STE emission shifts from 600 nm to 660 nm, which contributes to a larger spectral overlap between STE emission and the absorption of Yb3+ ions. As a result, the absolute NIR photoluminescence quantum yield reaches an unprecedented 50% in lead-free DPs via high-efficiency STE sensitization (>30%). The excellent optical performance of Cs2AgInCl6: Sb, Yb with high ambient, thermal and light stability makes it suitable for application in night-vision devices. Moreover, an ingenious dual-modal optical information encryption based on the combination of visible and NIR fluorescence printing patterns utilizing Cs2AgInCl6: Sb and Cs2AgInCl6: Sb, Yb respectively is successfully demonstrated. This study provides inspiration for designing highly efficient NIR-emitting Ln(3+)-doped DPs and illustrates their great potential in versatile optoelectronic applications.