Er3+/Yb3+‐Based Halide Double Perovskites with Highly Efficient and Wide Ranging Antithermal Quenching Photoluminescence Behavior for Light‐Emitting Diode Applications

Abstract Rare‐earth ion‐doped halide perovskite materials have attracted considerable attention owing to their outstanding electrical and optical characteristics. However, the heavy doping of activating rare‐earth ions causes severe cross‐relaxation and photoluminescence intensity quenching. Herein, the challenge of designing highly efficient emission and antithermal quenching Er 3+ /Yb 3+ ‐based halide double perovskite single crystals based on abnormal heavy activator doping without severe concentration quenching is addressed. Cross‐relaxation is proposed as a possible mechanism. Upon Yb 3+ substitution, the visible and near‐infrared (NIR) emission peaks at 664 and 995 nm are greatly enhanced, and the photoluminescence quantum yield of optimized Cs 2 NaEr 0.4 Yb 0.6 Cl 6 is 62% under 379 nm ultraviolet excitation. More importantly, the cross‐relaxation between Er 3+ and Yb 3+ is verified. The cross‐relaxation enhances the downshifting emission and causes the visible and NIR emissions to exhibit a wide range of antithermal quenching photoluminescence behaviors. The as‐prepared halide double perovskites demonstrate great potential for light‐emitting diode applications in advanced night vision technology and nondestructive examination.