Harvesting Sub-Bandgap IR Photons by Photothermionic Hot Electron Transfer in a Plasmonic p–n Junction

Abstract

Plasmonic semiconductors are an emerging class of low-cost plasmonic materials, and the presence of a bandgap and band-bending in these materials offer new opportunities to overcome some of the limitations of plasmonic metals. Here, we demonstrate that in a plasmonic p–n heterojunction (Cu2‑xSe-CdSe) the near-IR excitation (1.1 eV) of the hole plasmon in the p-Cu2–x Se phase results in rapid hot electron transfer to n-CdSe, with an energy 2.2 eV above the Fermi level. This hot electron generation and energy upconversion process can be well-described by a photothermionic mechanism, where the presence of a bandgap in p-Cu2–x Se facilitates the generation of energetic photothermal electrons. The lifetime of the transferred electrons in Cu2–x Se-CdSe can reach ∼130 ps, which is nearly 100× longer than that of its metal–semiconductor counterpart. This result demonstrates a novel approach for harvesting the sub-bandgap near IR photons using plasmonic p–n junctions and the potential advantages of plasmonic semiconductors for hot carrier-based devices.

Directional Damping of Plasmons at Metal–Semiconductor Interfaces

“…In addition, the ultrafast interfacial charge transfer can also be extended to plasmonic-semiconductor/semiconductor systems, especially for 1D or 2D heterostructures including common transition-metal chalcogenides and oxides, which have emerged as a series of new materials and exhibit fascinating new phenomena for some potential applications because of the extremely strong light–matter interactions arising from their suitable optical bandgaps in the NIR to the visible spectral range. For example, Yang et al experimentally and theoretically demonstrated that the NIR-excited hole plasmons in the plasmonic-Cu 2– x Se/CdSe heterostructures can induce rapid hot-electron transfer to CdSe, further improving the performance of plasmonic devices (Figure M, N) . Another work also confirmed the ultrafast hot-electron transfer from plasmonic-Cu 2– x S to 1T-MoS 2 in plasmonic-Cu 2– x S/1T-MoS 2 heterostructures (Figure O, P) …”

“…(M) Measured and (N) simulated transient absorption spectra of plasmonic-Cu 2– x Se/CdSe. Adapted from ref . Copyright 2021 American Chemical Society.…”

“…For example, Yang et al experimentally and theoretically demonstrated that the NIR-excited hole plasmons in the plasmonic-Cu 2−x Se/CdSe heterostructures can induce rapid hot-electron transfer to CdSe, further improving the performance of plasmonic devices (Figure 4M, N). 89 Another work also confirmed the ultrafast hot-electron transfer from plasmonic-Cu 2−x S to 1T-MoS 2 in plasmonic-Cu 2−x S/1T-MoS 2 heterostructures (Figure 4O, P). 90 Despite the efficient interfacial charge-carrier transfer at the plasmonic heterojunctions damped by plasmonic coupling, it usually requires overcoming the interfacial Schottky barrier.…”

Chemical Interface Damping in Nonstoichiometric Semiconductor Plasmonic Nanocrystals: An Effect of the Surrounding Environment

“…After dephasing, highly energetic carriers try to reach thermal equilibrium by hole–hole scattering and hole–phonon scattering, and as a consequence, the lattice reaches a higher temperature. , Later on, heat is dissipated to the surrounding environment by phonon–phonon scattering. , After pump excitation, the sequential plasmonic events are presented graphically in Figure . However, in the presence of the hole-accepting state, the photoexcited charge carrier can be easily transferred to the adjacent molecules. , In metal NPs, energetic hot electrons are transferred to the lowest unoccupied molecular orbitals of the adsorbate and also can be transferred to the conduction band of the adjacent semiconductor depending on the energy band diagram. ,, Similarly, for semiconductor plasmonic material, upon excitation the hot hole can be transferred to the adjacent highest occupied molecular state of the molecules as well as of the valence band of the adjacent semiconductor materials. − Figure demonstrate the CID effect in the presence of different surface ligands such as oleylamine (OLM) and 3-mercapto­propionic acid (3-MPA). The existence of the CID was evidenced by the accelerated dephasing process of plasmon and peak broadening of the LSPR.…”

Hot Electrons in TiO2–Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis

“…This is achieved by the generation and transfer of energetic charge carriers or “hot electrons” via resonant interaction of incident light with the collective and coherent motion of electrons in metal nanostructures to initiate, enhance, and promote photocatalytic activity. The exploitation of hot electrons produced by the localized surface plasmon resonance (LSPR) of noble metal nanoparticles in photocatalysis and photovoltaics has recently witnessed a surge of research interest [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. The research interest is well-deserved since optimal exploitation of hot electrons holds out the promise of high performance, durable photocatalysts for water treatment, solar hydrogen generation from water splitting, and CO 2 photoreduction.…”