Investigation of Two Photon Absorption of Ligand-Modified CsPbBr₃ Quantum Dots

The characteristics and application of nonlinear absorption from CsPbBr3 QDs film with the ligand-modified strategy have been investigated in this work. By means of a near-infrared fs Ti:sapphire laser as a light source, the up-conversion emission of CsPbBr3 QDs film of around 518 nm revealed a quadratic increase with the pump intensity. Through the temperature-dependent up-conversion emission, we obtained the binding energy and longitudinal optical (LO) phonon energy of CsPbBr3 QDs film of around 58.1 and 61.2 meV, respectively. Due to more active thermal coupling between the excited electron or hot phonon effect, the photon decay trace under two-photon excitation was prolonged at higher temperatures. The ligand-modified CsPbBr3 QDs film exhibits a relatively large TPA coefficient of around 28.6 cm/GW by the open aperture Z-scan measurement, and it has been demonstrated as a promising nonlinear medium to obtain the pulsewidth of ultrafast lasers.