Room temperature synthesis of cesium lead bromide perovskite magic sized clusters with controlled ratio of carboxylic acid and benzylamine capping ligands

We demonstrate the synthesis of cesium lead bromide (CsPbBr3) perovskite magic sized clusters (PMSCs) and how to control the transformation from CsPbBr3 perovskite quantum dots (PQDs) to PMSCs by varying the amount of organic carboxylic acids (CAs), including mesitylacetic acid (MAA), oleic acid (OA), and phenylacetic acid (PAA), along with benzylamine (BZA) as capping ligands at room temperature. The PQDs and PMSCs are characterized by means of XRD, UV/vis, photoluminescence (PL), time-resolved PL (TRPL), and X-rayphotoelectron spectroscopy (XPS). The concentration of CAs affects the excitonic absorption of both the CsPbBr3 PMSCs (λ = 389–428 nm) and CsPbBr3 PQDs (λ = 460–516 nm), with high concentration of CAs favoring CsPbBr3 PMSCs over PQDs. With PAA at 45.45 mM, pure CsPbBr3 PMSCs can be generated, which does not happen for MAA or OA, suggesting that PAA is a stronger ligand than MAA and OA. The results suggest that PMSCs require better passivation or stronger ligands than PQDs. This study establishes a simple and general method for synthesizing CsPbBr3 PMSCs using a combination of BZA and CA capping ligands as a highly effective dual passivation system.