Manipulating Charge Transfer from Core to Shell in CdSe/CdS/Au Heterojunction Quantum Dots

Abstract

The photophysics of charge transfer and recombination mechanisms in a heterojunction structure of CdSe/CdS/Au quantum dots (QDs) are studied by temperature-dependent steady-state photoluminescence (PL) and time-resolved PL (TRPL). We manipulate the charge transfer from core to shell surface by varying the tunneling barrier height resulted from temperature variation, and the barrier width resulted from shell thickness variation. The charge transfer process, which can be described by a tunneling transmission model, is manifested by two competitive recombination processes, an intrinsic exciton emission and a trap emission in the near-infrared (NIR) range. Our study establishes the photophysics foundation for core/shell/metal application in photocatalyst and optoelectronics.

Interfacial Charge Transfer Regulates Photoredox Catalysis

“…By appropriately designing the QD–molecule or QD–cocatalyst interface, charge transfer at a subpicosecond level can be achieved, surpassing the ultrafast intraband cooling process (Figure a). − However, the presence of defect states in QDs significantly affects interfacial charge transfer . These defect sites can either trap photogenerated charges from the bandgap or hot excitons, acting as charge transfer relays , or recombination centers, , leading to opposing directions of interfacial charge separation (see Figure b). QDs exhibit highly degenerate and quasi-discrete energy levels within a single unit, making them susceptible to multiexciton processes (Figure c) .…”

A promising type-II β-AsP/g-C6N6 van der Waals heterostructure photocatalyst for water splitting: a first-principles study

“…Exactly, the reduction potential (H + /H 2 ) and the oxidation potential (H 2 O/ O 2 ) of water are naturally sandwiched between the CBM and the VBM. The redox potential is related to the pH of water, and it has the following linear relationship: 57 E H+/H 2 = À4.44 eV + pH Â 0.059 eV (7) and…”

“…Traditional semiconductor catalysts often have the disadvantages of low conductivity, a narrow visible light absorption range, and a high carrier recombination rate. [5][6][7] Compared with the photocatalysts of bulk semiconductor materials, two-dimensional (2D) semiconductors show a better performance because of their large specific surface areas, which can prolong the lifetime of photogenerated charges. However, photogenerated electrons and photogenerated holes may easily accumulate on the catalyst surface, which will interact and recombine with each other.…”

Time-resolved and Temperature-dependent Broadband Emission of Plasmon-coupled Quantum Dots

“…Instead of surface passivation, which would reduce the surface-trapped state contribution, the use of plasmonic metal nanoparticles for PL enhancement is considered to increase the quantum yield considerably. Previous reports have documented the plasmonic effects on semiconductor QDs, [4,23,24,33] but the fractional contribution of temporal distributions and thermalization of the plasmon-coupled surface-trapped excitons has not been presented in full detail. Plasmonic NPs may reduce the nonradiative decay rate of semiconductor QDs when the plasmon-exciton coupling is much faster than the radiative and nonradiative decay of the QDs [4].…”