We report the quantitative compositional profiling of 3-5 nm CdSe/ZnS quantum dots (QDs) conjugated with a perfluorooctanethiol (PFOT) layer using the newly developed time-of-flight (TOF) medium-energy ion scattering (MEIS) spectroscopy with single atomic layer resolution. The collection efficiency of TOF-MEIS is 3 orders of magnitude higher than that of conventional MEIS, enabling the analysis of nanostructured materials with minimized ion beam damage and without ion neutralization problems. The spectra were analyzed using PowerMEIS ion scattering simulation software to allow a wide acceptance angle. Thus, the composition and core-shell structure of the CdSe cores and ZnS shells were determined with a 3% composition uncertainty and a 0.2-nm depth resolution. The number of conjugated PFOT molecules per QD was also quantified. The size and composition of the QDs were consistent with those obtained from high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. We suggest TOF-MEIS as a nanoanalysis technique to successfully elucidate the core-shell and conjugated layer structures of QDs, which is critical for the practical application of QDs in various nano- and biotechnologies.

Despite their comparable performance to commercial solar systems, lead-based perovskite (Pb-perovskite) solar cells exhibit limitations including Pb toxicity and instability for industrial applications. To address these issues, two types of Pb-free materials have been proposed as alternatives to Pb-perovskite: perovskite-based and non-perovskite-based materials. In this review, we summarize the recent progress on solar cells based on antimony/bismuth (Sb/Bi) chalcohalides, representing Sb/Bi non-perovskite semiconductors containing chalcogenides and halides. Two types of ternary and quaternary chalcohalides are described, with their classification predicated on the fabrication method. We also highlight their utility as interfacial layers for improving other solar cells. This review provides clues for improving the performances of devices and design of multifunctional solar systems.

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Antimony chalcoiodide, Sb(S,Se)I, has recently gained considerable attention as an alternative to Pb-based perovskites in next-generation solar cells. In this work, we propose an effective solution-processing method for fabricating Sb(S,Se)I alloy films with various S/Se ratios for solar cell applications. The proposed method involves two steps: the formation of Sb 2 (S,Se) 3 (step I) and its conversion to Sb(S,Se)I (step II). We introduced an additional deposition step based on a SbCl 3 -selenourea solution in step I to fabricate Sb(S,Se)I alloy with tunable properties. We controlled the growth of Sb(S 1−x Se x )I films (0 ≤ x ≤ 1) and investigated the effects of the S/Se molar ratio on the bandgap, crystalline phase, morphology, and electronic structure. Further, based on the results, we propose suitable electron-and hole-transporting layers for constructing antimony chalcoiodide solar cells. This study highlights the potential of Sb(S,Se)I as a solar absorber and provides some clues to construct Sb(S,Se)I solar cells.

Ternary chalcohalides are promising lead-free photovoltaic materials with excellent optoelectronic properties. We propose a simple one-step solution-phase precursor-engineering method for antimony selenoiodide (SbSeI) film fabrication. SbSeI films were fabricated by spin-coating the precursor solution, and heating. Various precursor solutions were synthesized by adjusting the molar ratio of two solutions based on SbCl3-selenourea and SbI3. The results suggest that both the molar ratio and the heating temperature play key roles in film phase and morphology. Nanostructured SbSeI films with a high crystallinity were obtained at a molar ratio of 1:1.5 and a temperature of 150 °C. The proposed method could be also used to fabricate (Bi,Sb)SeI.

In this report, cesium surface layers formed by Cs + ion bombardment on silicon and phenylalanine (Phe) samples were analyzed by TOF-MEIS and ToF-SIMS. Si wafers were bombarded with 500 eV Cs + ions, then were subsequently bombarded with five different Cs + fluences corresponding to the transient and equilibrium regimes. The Phe layers were evaporated on Si wafers, up to 100 nm thickness. The samples were subsequently bombarded at four different fluences. For Phe, TOF-MEIS shows the formation of a sharp Cs surface layer of~0.5 nm thickness, on which the peak height increases with Cs + ion bombardment and a long Cs tail builds up, penetrating deep into the subsurface. For Si, a similar Cs surface peak forms, but it saturates quickly compared to Phe.

In the current work, stable prenucleated PbS quantum dots (QDs) with a sub-nanometer (0.8 nm) size have been successfully synthesized via a systematically designed experiment. A detailed analysis of critical nucleation, growth, and stability for such ultrasmall prenucleated clusters is done. The experimental strategy is based on controlled concentration, temperature and injection of respective precursors, thus enabling us to control nucleation rate and separation of stable sub-nanometer PbS QDs with size 0.8 nm. Significantly, by providing additional thermal energy to sub-nanometer PbS QDs, we achieved the fully nucleated cubic crystalline structure of PbS with size of around 1.5 nm. The size and composition of the prenucleated QDs are investigated by sophisticated tools like X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) spectroscopy which confirms the synthesis of PbS with Pb2+ rich surface while the UV-Vis spectroscopy and X-ray diffraction (XRD) data suggests an alternative crystallization path. Non-classical nucleation theory is employed to substantiate the growth mechanism of prenucleated PbS QDs.