Several Orders-of-Magnitude Enhancement of Multiphoton Absorption Property for CsPbX₃ Perovskite Quantum Dots by Manipulating Halide Stoichiometry

Two-photon absorption (2PA) and three-photon absorption (3PA) processes feature many technological applications for fluorescence microscopy, photodynamic therapy, optical data storage, and so on, Herein, we reveal that the giant 2PA and 3PA properties for all-inorganic CsPbX3 (X = Cl, Br, I, and mixed Cl/Br and Br/I) perovskite quantum dots (PQDs) can be enhanced several orders of magnitude, respectively, by simply changing the halide stoichiometry at the X site. Notably, reported data show excellent 2PA and 3PA properties for CsPbI3 (σ2 ∼ 2.1 × 106 GM and σ3 ∼ 1.1 × 10–73 cm8 s3/photon3), which is 2–4 orders of magnitude higher than those of conventional red-emitting QDs and 5–7 orders of magnitude higher than well documented organic molecules. Experimental results show multiphoton absorption (MPA) cross sections can be adjusted 2–3 orders of magnitude by band gap engineering in a predictable manner, via increasing the Pauling electronegativity of the halide. Two-photon luminescence imaging data show that PQDs can be used for very good multiphoton imaging applications. Importantly, reported results provide a new strategy for manipulating MPA properties by halide composition engineering which will be instrumental in the design of next-generation technological devices