Efficient and Stable Red Perovskite Light‐Emitting Diodes with Operational Stability >300 h

Abstract The long‐term operational stability of perovskite light‐emitting diodes (PeLEDs), especially red PeLEDs with only several hours typically, has always faced great challenges. Stable β‐CsPbI 3 nanocrystals (NCs) are demonstrated for highly efficient and stable red‐emitting PeLEDs through incorporation of poly(maleic anhydride‐ alt ‐1‐octadecene) (PMA) in synthesizing the NCs. The PMA can chemically interact with PbI 2 in the precursors via the coupling effect between O groups in PMA and Pb 2+ to favor crystallization of stable β‐CsPbI 3 NCs. Meanwhile, the cross‐linked PMA significantly reduces the Pb Cs anti‐site defect on the surface of the β‐CsPbI 3 NCs. Benefiting from the improved crystal phase quality, the photoluminescence quantum yield for β‐CsPbI 3 NCs films remarkably increases from 34% to 89%. The corresponding red‐emitting PeLEDs achieves a high external quantum efficiency of 17.8% and superior operational stability with the lifetime, the time to half the initial electroluminescence intensity ( T 50 ) reaching 317 h at a constant current density of 30 mA cm −2 .