Overcoming the Ambient Manufacturability-Performance Bottleneck in Perovskite Nanocrystal Emitters for Efficient Light-Emitting Diodes.

Colloidal perovskite nanocrystals (NCs) have risen rapidly in luminescence efficiency and color purity. However, their high performance requires careful and complex pre-treatment of precursors and precise regulation of the reaction atmosphere; otherwise, their emission will be weak and broad. To overcome these limitations, we develop a facile ligand exchange method using a new type of bidentate ligand, which is obtained by reacting cheap sulfur with tributylphosphine (S-TBP). During ligand exchange, the double bond between P and S atoms breaks and a single bond is formed between them, after which S-TBP switches into a bidentate ligand and binds to a perovskite NC at two points. With short-chain S-TBP ligands that have high spatial position resistance, both NC spacing and surface ligand density can be reduced, thereby improving carrier injection and transport. On the NC surface after ligand exchange, halogen vacancies were substantially filled, leading to a PbSP (Pb, S, and P elements) component-dominated shell that greatly decreases trap density and enhances material stability. The resulting perovskite NCs are stable and bright with a photoluminescence quantum yield of ≈96 %, and an external quantum efficiency of 22 %. Note that our ligand-exchange strategy remains effective even when scaling up, which should accelerate commercialization.