Deep‐Blue CsPbBr3 Perovskite Quantum Dots via Green Polar Solvent and Short Ligand Engineering towards Highly Efficient Light‐Emitting Diodes

Abstract To date, researchers face a huge challenge in synthesizing blue perovskite quantum dots (PQDs) with short‐chain ligands since the short‐chain ligands increase the polarity and decrease solubility in common non‐polar solvents during syntheses. The use of polar solvents to replace non‐polar ones may solve the solution problem, but polar solvents will decompose PQDs. So, the key to successful synthesis of PQDs with short‐chain ligands is to find polar solvents that can dissolve short‐chain ligands well and do not destroy perovskites concurrently. Herein, a room‐temperature synthesis method for deep‐blue CsPbBr 3 PQDs with short‐chain ligands is proposed by using eco‐friendly ethyl acetate polar solvent. CsPbBr 3 PQDs with an average size of 3.87 nm and a peak wavelength of 454 nm are synthesized with a photoluminescence quantum yield of 48.4%. With an interlayer modification to the hole transport layer, the deep‐blue perovskite light‐emitting diodes realize a maximum external quantum efficiency of 4.39% and half‐lifetime of 4.5 min at a maximum brightness of 72 cd m −2 . This work offers a novel eco‐friendly avenue for the preparation of effective PQDs including blue ones, which will accelerate commercialization of PQDs in lighting and HD full‐color displays as well as reduce discharge of solvent pollutants and protect the global environment.