Eu²⁺‐doped MAPbBr₃ Perovskite Nanocrystal in Silica Composites with Enhanced Stability for White Light Emission and Flexible X‐Ray Detectors

Abstract Perovskite nanocrystals (NCs), such as MAPbX₃ (MA⁺ = methylammonium; X = Cl, Br, or I), have received attention owing to their excellent optoelectronic properties and ease of integrating with flexible substrates. Lanthanide ion doping is widely used as an effective strategy to enhance the optoelectronic performance of perovskite NCs. However, incorporating the lanthanide dopant and ensuring the emission stability of the perovskite NCs in high‐performance optoelectronic devices remains a major challenge. Herein, the synthesis of Eu²⁺‐doped MAPbBr₃ NCs within the channels of SBA‐15 is presented to improve their stability. The doped MAPbBr₃ NC@SBA‐15 composites exhibit significantly improved stability than that of undoped MAPbBr₃ NCs. The doped MAPbBr₃ NC@SBA‐15 composites exhibit moderate PL quantum yields and excellent stability under ambient conditions and UV irradiation. In addition, the MAEu_0.3Pb_0.7Br₃ NC@SBA‐15 composite applied in white‐light‐emitting diodes (WLEDs) achieves a color rendering index of 73.5. Moreover, MAEu_0.3Pb_0.7Br₃ NC@SBA‐15 can be combined with styrene‐ethylene‐butylene‐styrene to fabricate a flexible direct X‐ray detector, realizing a high sensitivity of 7592.2 µC Gy_air⁻¹ cm⁻² and a low detection limit of <77 nGy_air s⁻¹; this is an outstanding value for a NC‐based flexible direct X‐ray detector. This work serves as a guide for the design of perovskite NCs for both WLEDs and flexible X‐ray detectors.