Relaxation of Plasmon-Induced Hot Carriers

Abstract

Plasmon-induced hot carrier generation has attracted much recent attention due to its promising potential in photocatalysis and other light harvesting applications. Here we develop a theoretical model for hot carrier relaxation in metallic nanoparticles using a fully quantum mechanical jellium model. Following pulsed illumination, nonradiative plasmon decay results in a highly nonthermal distribution of hot electrons and holes. Using coupled master equations, we calculate the time-dependent evolution of this carrier distribution in the presence of electron–electron, electron–photon, and electron–phonon scattering. Electron–electron relaxation is shown to be the dominant scattering mechanism and results in efficient carrier multiplication where the energy of the initial hot electron–hole pair is transferred to other multiple electron–hole pair excitations of lower energies. During this relaxation, a small but finite fraction of electrons scatter into luminescent states where they can recombine radiatively with holes by emission of photons. The energy of the emitted photons is found to follow the energies of the electrons and thus redshifts monotonically during the relaxation process. When the energies of the electrons approach the Fermi level, electron–phonon interaction becomes dominant and results in heating of the nanoparticle. We generalize the model to continuous-wave excitation and show how nonlinear effects become important when the illumination intensity increases. When the temporal spacing between incident photons is shorter than the relaxation time of the hot carriers, we predict that the photoluminescence will blueshift with increasing illumination power. Finally, we discuss the effect of the photonic density of states (Purcell factor) on the luminescence spectra.

Radiation dominated implosion with nano-plasmonics

“…Apart of the large cross section of plasmon excitations, which can enhance the geometrical cross section of the nanoantennas by several orders of magnitude, surface plasmon resonance excitation is a much more efficient process for the quantum mechanical "hot carrier" generation. This process is much faster than the heating via the external hohlraum, and its typical time-scale is around 10-500 fs 33 . This is by orders of magnitude shorter than the irradiation pulse length.…”

Quantifying hot carrier and thermal contributions in plasmonic photocatalysis

“…This process requires resonant conditions between the hot carriers and the acceptor levels of the Ru-N surface species (dark red and yellow dashed arrows in the inset). Once created by plasmon decay, hot carriers rapidly relax toward the Fermi level through a carrier multiplication process induced by electron-electron scattering (31). Electron-phonon scattering on a monometallic particle plays a relatively minor role, because such phonons involve atoms of the same charges and do not possess electrical multipolar moments.…”

Efficient Hot‐Electron Transfer under Modal Strong Coupling Conditions with Sacrificial Electron Donors

“…Furthermore, a fundamental understanding of hot‐carriers is still limited. The energy distributions of hot‐electrons and hot‐holes should be determined experimentally in addition to theoretical calculations . Time‐resolved measurements of the near‐ and far‐field optics are also important to understand the plasmon decay and the generation and transport of photocarriers…”