Nonlinear Optical Properties of Cs 2 AgIn 1- x Bi x Cl 6 Single Crystals.

Lead-free double perovskites offer enhanced stability and lower toxicity compared to their lead-based counterparts. Dual B-site cations can introduce elemental and structural diversity into double perovskite materials, enabling fine-tuning of the optical properties. However, the study of the nonlinear optical (NLO) properties of lead-free double perovskites is still nascent, hindering their relevant potential applications. Based on this, this work synthesizes a series of Cs 2 AgIn 1- x Bi x Cl 6 ( x = 0, 0.1, 0.25, 0.75, 1) single crystals, with the aim to explore the impact of composition on their NLO properties. Interestingly, Cs 2 AgInCl 6 shows surface defect-induced second harmonic generation. With increasing Bi 3+ concentration, the multiphoton absorption coefficients of Cs 2 AgIn 1- x Bi x Cl 6 single crystals increase as a result of increasing state density. This work is helpful to understand well the NLO properties of lead-free double perovskites, laying a foundation for the development of related applications.