Photoluminescence kinetics of CsPbBr 3 nanocrystals with urea as co-ligand by using ultrafast spectroscopy

All-inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) are widely recognized as promising materials for optoelectronic devices. This is due to their ability to exhibit a variable band gap, narrow emission properties, and high photoluminescence quantum yield (PLQY). However, the use of traditional ligands like alkyl acid and amine could not anchor NCs tightly. Consequently, this has led to inefficient passivation of surface defects and poor stability of CsPbX 3 NCs. In this study, we present the preparation of CsPbBr 3 nanocrystals using the room temperature saturation recrystallization method with urea as a co-ligand. Urea, a small molecule ligand with bifunctional groups, acts as a zwitterionic ligand and effectively modifies the surface state of CsPbBr 3 nanocrystals through its C=O and N–H functional groups. The as-prepared CsPbBr 3 nanocrystals, with a photoluminescence quantum yield (PLQY) of up to 80%, exhibit improved water stability compared to pristine CsPbBr 3 nanocrystals. X-ray diffraction and photoluminescence (PL) results demonstrate that the addition of urea as a co-ligand promotes crystallization and enhances the emission intensity of CsPbBr 3 . Meanwhile, the photoluminescence mechanism of CsPbBr 3 NCs was investigated using ultrafast transient absorption and time-resolved photoluminescence spectroscopy. This study presents a straightforward ligand-assisted method for preparing stable CsPbBr 3 NCs with high PLQY, while also enhancing the understanding of the interaction between ligands and the PL properties of CsPbBr 3 NCs.