Investigation of dielectric, linear, and nonlinear optical properties of synthesized 2D Ruddlesden-Popper-type halide perovskite.

• The optical indexes of synthesized BA 2 MAPb 2 I 7 perovskites were determined. • The optical bandgap was obtained at ∼ 1.95 eV for BA 2 MAPb 2 I 7 thin films. • The NLO properties of BA 2 MAPb 2 I 7 thin films was studied by Z-scan method with different laser powers. Ruddlesden-Popper-type halide perovskites (RPPs) have been widely investigated because of their tunable optical properties. The BA 2 MAPb 2 I 7 (BA = CH 3 (CH 2) 3 NH 3 and MA = CH 3 NH 3) powder is synthesized by a chemical solution-based method at low temperature and deposited on a glass substrate by spin coating technique. The optical transmission, reflection, and absorption investigations are conducted to determine the optical constants of the nano-powder and thin film of BA 2 MAPb 2 I 7. The obtained results reveal that the optical band gap energy of BA 2 MAPb 2 I 7 thin film and BA 2 MAPb 2 I 7 nanoparticles are ∼ 1.95 and ∼ 2.02 eV, which is close to the photoluminescence (PL) peak at around 2.15 eV (576 nm). The optical indexes such as n, k, ε 1, and ε 2 are assessed based on reflectance spectra data and the Kramers-Kronig (KK) method. Moreover, the third-order nonlinear optical (NLO) characteristics, including nonlinear absorption coefficient (β), nonlinear refractive index (n 2), third-order susceptibility (χ (3) ) and second-order hyperpolarizability (γ) are investigated at different laser power. The positive signs of the n 2 and β reveal that the BA 2 MAPb 2 I 7 thin film exhibits self-focusing and saturable absorption (SA) properties due to thermal nonlinearity under the continuous wave (CW) laser regime. The magnitude of χ 3 is from 20.275 × 10 - 2 to 29.908 × 10 - 2 e s u and the value of γ is from 19.633 × 10 - 27 to 28.961 × 10 - 27 e s u. The superior NLO responses of BA 2 MAPb 2 I 7 thin-film open the path for the future design and synthesis of desirable and distinct materials for optoelectronic devices. [ABSTRACT FROM AUTHOR]