Dotierte Halbleiter-Nanokristalle: Lumineszenz, plasmonische und magnetische Eigenschaften

The impact of spatially heterogeneous chemical doping on the electronic properties of CdSe quantum dots: insights from ab initio computation

The introduction of copper (Cu) impurity in semiconductor CdSe quantum dots (QDs) gives rise to unique photoluminescence (PL) bands exhibiting distinctive characteristics, like broad line width, significant Stokes shift, and complex temporal decay. The atomistic origins of these spectral features are yet to be understood comprehensively. We employed multiple computational techniques to systematically study the impact of the spatial heterogeneity of Cu atoms on the stability and photophysical properties, including the emission linewidth of doped QDs under ambient conditions. The Cu substitution introduces a spin-polarized intragap state, the energetic position of which is strongly dependent on the dopant location and causes spectral broadening in QD ensembles. Furthermore, the dopant dynamics under ambient conditions are significantly influenced by the specific arrangement of Cu within the QDs. The dynamic electronic structures of surface-doped CdSe illustrate more pronounced perturbations and vary the mid-gap state position more drastically than those of the core-doped QDs. Vibronic coupling broadens the photoluminescence peaks associated with the conduction band-to-defect level transition for individual QDs. These insights into the dynamic structure-photophysical property relationship suggest viable approaches, such as tuning the operational temperature and selective co-doping, to enhance the functional performances of doped CdSe QDs strategically.

Photoluminescence Quenching in CsPbCl3 upon Fe Doping: Colloidal Synthesis, Structural and Optical Properties

Doped perovskite lead halide nanocrystals (PHNCs) are promising materials for various optoelectronic applications, but the major challenge faced by the researchers is the inability to dope foreign elements into perovskite lattice because of the strong lead-halide bond energies. In this work, we have used Fe as a dopant in CsPbCl₃ to explore different doping techniques based on the colloidal synthesis of PHNCs to investigate the advantages and disadvantages of different techniques. We are able to dope a relatively higher amount of Fe (∼10%) than reported and observe clear optical signatures when the precursor does not have pre-existing Pb-Cl bonds. We prove that there are two competing processes inside a doped PHNC - one is the effect of dopant energy levels, and the other is surface passivation by halide ions. Using the most optimal synthesis strategy, we show that although Fe does act as a luminescence quencher in perovskite similar to II-VI quantum dots (QDs), the quenching requires much more Fe compared to trace amounts of Fe required in traditional QDs. Our work will assist in giving an overall comparative idea of doping and finding the most optimized strategy and help identify the underlying physical processes in perovskite based QDs.