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Potential well
About: Potential well is a research topic. Over the lifetime, 1430 publications have been published within this topic receiving 30812 citations.
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TL;DR: Time-resolved PL analysis for both the perovskite QDs reveals faster life time compared to their bulk counterparts, confirming the significant radiative recombination of carriers in the QDs at the room temperature, and the quantitative analysis of the PL emission energy vs QD size shows an excellent fit with the Brus equation confirming the strong quantum confinement effect.
34 citations
TL;DR: In this article, the photothermal deflection spectroscopy (PDS) experiment was used to evaluate the average radius of semiconductor microcrystals and the time dependence of optically induced degradation in CdS and CdSe semiconductor-doped glasses.
Abstract: We report on the observation of the quantum confinement effect by using photothermal deflection spectroscopy (PDS) experiment and the time dependence of optically induced degradation in CdS and CdSe semiconductor‐doped glasses. The observed absorption peaks in the PDS experiment, together with a simple model, were used to evaluate the average radius of semiconductor microcrystals. It is found that the estimated average radii of quantum dots are consistent with that obtained from other methods. This result demonstrates that the PDS technique provides an alternative tool for the study of the optical properties of semiconductor microscrystals. The time dependence of the luminescence degradation of the impurity band, which is attributed to the process of Auger ionization, follows a stretched‐exponential function. The inconsistency with the previously proposed exponential relaxation may be due to the size distribution of CdS and CdSe microcrystals.
34 citations
TL;DR: In this article, three lower-dimensional derivatives of the ABX3 (A = monocation, X = halide) single perovskites were synthesized, including a quasi-1D derivative (1'-Tl).
Abstract: Quantum confinement effects in lower-dimensional derivatives of the ABX3 (A = monocation, X = halide) single perovskites afford striking optical and electronic changes, enabling applications ranging from solar absorbers to phosphors and light-emitting diodes. Halide double perovskites form a larger materials family, known since the late 1800s, but lower-dimensional derivatives remain rare and prior work has revealed a minimal effect of quantum confinement on their optical properties. Here, we synthesize three new lower-dimensional derivatives of the 3D double perovskite Cs2AgTlBr6: 2D derivatives with mono- (1-Tl) and bi-layer thick (2-Tl) inorganic sheets and a quasi-1D derivative (1'-Tl). Single-crystal ellipsometry studies of these materials show the first clear demonstration that dimensional reduction can significantly alter the optical properties of 2D halide double perovskites. This large quantum confinement effect is attributed to the substantial electronic delocalization of the parent 3D Ag–Tl perovskite. Calculations track the evolution of the electronic bands with dimensional reduction and the accompanying structural distortions and show a direct-to-indirect bandgap transition as the 3D perovskite lattice is thinned to a monolayer in 1-Tl. This bandgap transition at the monolayer limit is also evident in the calculations for 1-In, an isostructural, isoelectronic analogue to 1-Tl in which In3+ replaces Tl3+, underscoring the orbital basis for the direct/indirect nature of the bandgap. Thus, in complement to the massive compositional diversity of halide double perovskites, dimensional reduction may be used as a systematic route for harnessing electronic confinement effects and obtaining new electronic structures.
34 citations
TL;DR: In this article, a hierarchical porous silicon with nanopores in macropores structure (NP-MPSi) was fabricated through electro-assisted chemical etching using a silicon wafer as a substrate.
Abstract: In this work, hierarchically porous silicon was fabricated through electro-assisted chemical etching using a silicon wafer as a substrate. Pores with an average diameter of ca. 1200 nm (macropores) were observed and a large number of nanopores with a diameter of less than 5 nm were uniformly distributed over the surface of the macropore, forming the hierarchically porous silicon with nanopores in macropores structure (NP-MPSi). UV–vis diffuse reflection measurements indicated that NP-MPSi has a bandgap of 2.12 eV, which is 1.0 eV higher than that of the original silicon wafer because of the quantum confinement effect caused by the nanopores. Mott–Schottky experiments further demonstrated that the increase in bandgap of NP-MPSi arises from a positive shift of the valence band potential, which improves its capability for photocatalytic oxidation. NP-MPSi exhibited higher photoelectrochemical stability than macroporous silicon (MPSi), a comparison sample lacking nanopores. Using phenol as an example, photocatalytic experiments under irradiation with a Xe lamp demonstrated that the kinetic constants of phenol degradation and total organic carbon removal using NP-MPSi were nearly 3.5 and 8.0 times larger, respectively, than those using MPSi. This unique porous silicon material is therefore an attractive photocatalyst for environmental applications.
33 citations
TL;DR: In this paper, an efficient tuning mechanism of the light harvesting and detection of Ge quantum dots (QDs) was reported, where thin films of SiGeO alloys, produced by rf-magnetron sputtering, were annealed at 600°C in N2 to induce precipitation of small amorphous Ge QDs into the oxide matrix.
33 citations