Near‐Unity Quantum Yield in All‐Inorganic Double Perovskite Resistant to Thermal Quenching for Flexible Wearable Sensor

ABSTRACT

All‐inorganic lead‐free halide double perovskites draw extensive interest because they are eco‐friendly, structurally tunable, and possess photoelectric properties. Nevertheless, developing perovskites that combine ultra‐high quantum yield and multi‐environment stability remains a tremendous challenge. Herein, we use a simple low‐temperature route at ambient pressure to fabricate Cs ₂ NaTb _{1‐ x} Lu _x Cl ₆ perovskite microcrystals with different Lu ³⁺ doping concentrations. Through optimization of the Lu ³⁺ doping concentration, Cs ₂ NaTb _0.84 Lu _0.16 Cl ₆ perovskite microcrystals achieve a photoluminescence quantum yield (PLQY) approaching the theoretical limit, reaching up to 98.49%. Additionally, the perovskite microcrystals exhibit excellent thermal quenching resistance, with only a 7.3% decrease in luminescence intensity at 428 K. Density functional theory (DFT) calculations confirm that strong exciton localization is the key electronic mechanism for the high quantum yield. Moreover, Cs ₂ NaTb _0.84 Lu _0.16 Cl ₆ perovskite microcrystals are combined with aramid‐chopped fibers (ACFs) and polyphenylene sulfide (PPS) composite fibers, and the resultant luminescent fibers exhibit excellent photostability under extreme environmental conditions. Notably, the composite fiber exhibits significant piezoelectric properties. A sensor based on this composite fiber achieves a maximum output voltage of approximately 90 V. This Lu ³⁺ doping strategy offers a reliable pathway to advanced flexible optoelectronics and wearable sensing devices.