Abstract：
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.
摘要：
胶体钙钛矿纳米晶体（NC）的发光效率和色纯度迅速提高。然而,它们的高性能需要对前体进行仔细和复杂的预处理，并精确调节反应气氛；否则，它们的排放将是微弱和广泛的。为了克服这些限制,我们开发了一种使用新型双齿配体的简便配体交换方法，其通过使廉价的硫与三丁基膦(S-TBP)反应而获得。在配体交换期间，P和S原子之间的双键断裂，它们之间形成单键，之后，S-TBP转换为双齿配体，并在两点与钙钛矿NC结合。对于具有高空间位置电阻的短链S-TBP配体，NC间距和表面配体密度都可以降低，从而改善载流子注入和传输。在配体交换后的NC表面上，卤素空位已基本填满，导致PbSP(Pb，S,和P元素）以组分为主的壳，大大降低了陷阱密度并增强了材料的稳定性。所得钙钛矿NC稳定明亮，光致发光量子产率约为96%，和22％的外部量子效率。请注意，即使扩大规模，我们的配体交换策略仍然有效，这将加速商业化。
