Investigation of Two Photon Absorption of Ligand-Modified CsPbBr 3 Quantum Dots.

The characteristics and application of nonlinear absorption from CsPbBr 3 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 CsPbBr 3 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 CsPbBr 3 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 CsPbBr 3 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.