Enhanced optical limiting of CsPbBr₃ quantum dot-rGO hybrids: a comparison with pristine CsPbBr₃ quantum dots in...

Lead halide perovskite quantum dots (PQDs) have garnered considerable attention in the past decade owing to their remarkable optoelectronic characteristics; however, reports on their optical limiting performance in combination with graphene remain limited. In this work, we synthesised CsPbBr₃ PQDs-reduced graphene oxide (rGO) composites with different weight percentages via a facile, room-temperature method under air atmospheric conditions. Structural, optical, and time-resolved spectroscopic analyses confirm strong electronic coupling between CsPbBr₃ PQDs and rGO, indicating efficient charge transfer at the interface. The composites exhibit improved excited-state dynamics with faster carrier transfer compared to pristine CsPbBr₃. A comparative study between thin films and liquid samples of CsPbBr₃ PQDs was also carried out, assessing the effect of the material's form on its nonlinear absorption performance. Third-order nonlinear optical behaviour was investigated using Z-scan measurements with a 532 nm nanosecond pulsed laser. All of the samples displayed a reverse saturable absorption pattern involving two-photon absorption, along with enhanced optical limiting thresholds, highlighting the synergistic effect of perovskite-rGO nonlinear absorption. Notably, the CsPbBr₃ PQDs-40% rGO composite showed the highest nonlinear absorption coefficient (2.27 × 10^-10 m W^-1) and the lowest optical limiting threshold (0.86 × 10¹² Wm^-2), demonstrating superior optical limiting performance. Interestingly, the material demonstrated optical limiting behaviour both in liquid and thin film phases. Our findings reveal that CsPbBr₃ PQDs-rGO composites offer enhanced optical limiting compared to their individual counterparts, highlighting their potential for next-generation photonic protection devices. This work provides new insights into exploiting perovskite-carbon hybrid nanostructures as efficient optical limiters.