Effect of CsPbBr3 quantum dots with different X-type ligands as additives on third-order nonlinear optical response in perovskite thin films

This work investigates the characteristics and applications of nonlinear optical (NLO) parameters—including the nonlinear refractive index (n₂), nonlinear absorption coefficient (β), and susceptibility—in triple-cation perovskite thin films with incorporated CsPbBr₃ quantum dots (QDs) capped with two different ligands (DDAB and OAm&OA) at varying concentrations. Ligands, by altering the electronic environment and surface structure, can enhance the density of active electrons involved in light-matter interactions. The highest values of n₂ and β were observed in PSK@QD(OAm&OA) at a concentration of 0.15 mg/ml, with values of 1.89 × 10⁻⁵ cm²/W and 4.24 × 10⁻¹ cm/W, respectively. Incorporated QDs with different ligands at various concentrations significantly influenced the nonlinear absorption mechanism. Additionally, the impact of incorporated CsPbBr₃ QDs with different X-type ligands on the transverse optical (TO) and longitudinal optical (LO) phonon modes was studied. The polarizability and distinct ring structures of the ligands also affected the NLO responses. These results indicate that these materials have significant potential for applications in optical communications, sensing, and various optoelectronic devices, as their nonlinear properties can be fine-tuned by modifying the QDs ligands and the QDs concentrations.