Room temperature precipitated dual phase CsPbBr₃-CsPb₂Br₅ nanocrystals for stable perovskite light emitting diodes

Although the efficiency of metal halide perovskite light emitting diodes (PeLEDs) has been improved to an attractive level, the poor stability of perovskite emitting layers is a major concern for the application of PeLEDs. Herein, we report a facile ligand-assisted precipitation synthesis of stable dual-phase CsPbBr₃-CsPb₂Br₅ nanocrystals (NCs) for improving the stability of PeLEDs. In our synthetic process, the bromide-rich circumstance is beneficial to generate high quality dual-phase perovskite NCs with PLQY as high as 92% and a narrow emission linewidth (19 nm). More importantly, as-synthesized dual phase perovskite NCs exhibit extremely high thermal stability in heating tests in air with a considerable humidity of 30%-55% in comparison with previously reported single phase CsPbBr₃ NCs. The aforementioned advantages of our synthesized dual-phase CsPbBr₃-CsPb₂Br₅ NCs allow for the fabrication of light emitting layers of PeLEDs under ambient conditions. The fabricated green PeLED based on CsPbBr₃-CsPb₂Br₅ NCs shows a low turn-on voltage of 2.5 V and a high brightness of 8383 cd m^-2 at 8 V. Owing to the high stability of dual-phase CsPbBr₃-CsPb₂Br₅ NCs, the fabricated PeLED also exhibits better operational stability in comparison with those PeLEDs based on single phase CsPbBr₃ NCs. Our work presents a new route to fabricate stable perovskite light-emitting diodes using room temperature precipitated dual-phase CsPbBr₃-CsPb₂Br₅ NCs as emitting layer materials.