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

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 MAEu0.3Pb0.7Br3 NC@SBA‐15 composite applied in white‐light‐emitting diodes (WLEDs) achieves a color rendering index of 73.5. Moreover, MAEu0.3Pb0.7Br3 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 Gyair−1 cm−2 and a low detection limit of