Cs2AgBiBr6@TiO2 nanocomposites with enhanced nonlinear absorption and electrochemical properties

Abstract

To solve the toxicity and stability issues of traditional lead halide perovskites, Cs₂AgBiBr₆@TiO₂ nanocomposites were synthesized via a thermal injection method. Cs₂AgBiBr₆ quantum dots (QDs) and Cs₂AgBiBr₆@TiO₂ nanocomposites were dispersed in methyl methacrylate (MMA) to prepare (Cs₂AgBiBr₆)₆/PMMA and (Cs₂AgBiBr₆@TiO₂)₆/PMMA organic glasses (OGs). The nonlinear absorption (NLA) properties of the materials were investigated using the open-aperture Z-scan technique, revealing that after compositing with TiO₂, the reverse saturable absorption (RSA) coefficient of the (Cs₂AgBiBr₆@TiO₂)₆/PMMA OG increased from 194 cm GW⁻¹ to 294 cm GW⁻¹ at an energy of 10 µJ. This is attributed to the incorporation of TiO₂, which facilitates interfacial charge separation and accelerates electron transfer, thereby significantly enhancing the RSA of Cs₂AgBiBr₆@TiO₂. Under identical testing conditions, the optical limiting thresholds of the (Cs₂AgBiBr₆)₆/PMMA and the (Cs₂AgBiBr₆@TiO₂)₆/PMMA OGs were measured to be 5.33 J cm⁻² and 3.87 J cm⁻², respectively. Compared to the (Cs₂AgBiBr₆)₆/PMMA OG, the (Cs₂AgBiBr₆@TiO₂)₆/PMMA OG demonstrates superior optical limiting performance. Electrochemical impedance spectroscopy (EIS) measurements demonstrated that Cs₂AgBiBr₆@TiO₂ exhibits lower impedance (R_ct) and favorable photocurrent response (0.61 µA cm⁻²), confirming its efficient charge separation/transport capability, which further promotes the RSA effect of Cs₂AgBiBr₆@TiO₂. These results indicate that Cs₂AgBiBr₆@TiO₂ holds promising potential for applications in optical limiting devices.