Beyond Charge Transfer: The impact of auger recombination and FRET on PL quenching in an rGO-QDs system

PL intensity quenching and the PL lifetime reduction of fluorophores located close to gra‐ phene derivatives are generally explained by charge and energy transfer processes. Analyzing the PL from PbS QDs in rGO/QD systems, we observed a substantial reduction in average PL lifetimes with an increase in rGO content that cannot be interpreted solely by these two processes. To explain the PL lifetime dependence on the rGO/QD component ratio, we propose a model based on the Auger recombination of excitations involving excess holes left in the QDs after the charge transfer process. To validate the model, we conducted additional experiments involving the external engi‐ neering of free charge carriers, which confirmed the role of excess holes as the main QD PL quench‐ ing source. A mathematical simulation of the model demonstrated that the energy transfer between neighboring QDs must also be considered to explain the experimental data carefully. Together, Au‐ ger recombination and energy transfer simulation offers us an excellent fit for the average PL life‐ time dependence on the component ratio of the rGO/QD system

Engineering the Optical Properties of CsPbBr₃ Nanoplatelets through Cd²⁺ Doping

Lead halide perovskite nanoplatelets (NPls) attract significant attention due to their exceptional and tunable optical properties. Doping is a versatile strategy for modifying and improving the optical properties of colloidal nanostructures. However, the protocols for B-site doping have been rarely reported for 2D perovskite NPls. In this work, we investigated the post-synthetic treatment of CsPbBr3 NPls with different Cd2+ sources. We show that the interplay between Cd2+ precursor, NPl concentrations, and ligands determines the kinetics of the doping process. Optimization of the treatment allows for the boosting of linear and nonlinear optical properties of CsPbBr3 NPls via doping or/and surface passivation. At a moderate doping level, both the photoluminescence quantum yield and two-photon absorption cross section increase dramatically. The developed protocols of post-synthetic treatment with Cd2+ facilitate further utilization of perovskite NPls in nonlinear optics, photonics, and lightning

Stoichiometry Control in Dual-Band Emitting Yb³⁺-Doped CsPbCl_<i>x</i>Br_3–<i>x</i> Perovskite Nanocrystals

Perovskite nanocrystals (NCs) are currently one of the most efficient optical materials in the visible spectral range. Much attention is paid to extending their efficiency to the near-infrared (NIR) spectral region, which will significantly benefit their applications in optoelectronics, photonics, and biomedicine. To further promote this effort, we developed a novel synthetic approach to dual-band emitting Yb3+-doped perovskite NCs, whose stoichiometry and hence the position of the visible photoluminescence can be tuned independently of the Yb3+-precursor. The intensity of the NIR emission from Yb3+ ions shows a notable nonlinear dependence on the excitation power. To describe the corresponding redistribution of the photoluminescence intensities between the emissive channels, we developed a theoretical description of the relaxation dynamics in the doped NCs, including both the energy transfer and quantum cutting processes. Finally, we showed that the dual-band photoluminescence in the doped NCs can be excited via two-photon absorption. Our findings thus pave the way for new nanomaterials that can be operated entirely in the NIR spectral range