Hot carrier multiplication in plasmonic photocatalysis

Light-induced hot carriers derived from the surface plasmons of metal nanostructures have been shown to be highly promising agents for photocatalysis. While both nonthermal and thermalized hot carriers can potentially contribute to this process, their specific role in any given chemical reaction has generally not been identified. Here, we report the observation that the H2–D2 exchange reaction photocatalyzed by Cu nanoparticles is driven primarily by thermalized hot carriers. The external quantum yield shows an intriguing S-shaped intensity dependence and exceeds 100% for high light intensities, suggesting that hot carrier multiplication plays a role. A simplified model for the quantum yield of thermalized hot carriers reproduces the observed kinetic features of the reaction, validating our hypothesis of a thermalized hot carrier mechanism. A quantum mechanical study reveals that vibrational excitations of the surface Cu–H bond is the likely activation mechanism, further supporting the effectiveness of low-energy thermalized hot carriers in photocatalyzing this reaction.

Монополярное умножение горячих носителей заряда в полупроводниках A-=SUP=-III-=/SUP=-B-=SUP=-V-=/SUP=- в сильном электрическом поле и бесшумные лавинные фотодиоды (О б з о р)

The results of theoretical and experimental studies of impact ionization processes and charge carrier heating in multi-valley A3B5 semiconductors at high electric field are presented and their relationship with the features of the band structure is discussed. A role of subsidiary L- and X-valleys, complex structure of the valence band and orientation dependence of the ionization coefficients are taken into account. A new approach to the choice of semiconductor materials with a large ratio of the ionization coefficients of holes and electrons to create the noiseless avalanche photodiodes due to monopolarity of hot charge carrier multiplication is proposed.

Excited Carrier Dynamics in Two-dimensional Materials

When electrons in materials are excited, they undergo several dynamic processes such as carrier thermalization, transfer, and recombination. These fundamental excited state processes are crucial to understanding the microscopic principles at work in electronic and optoelectronic devices. This article introduces the excited carrier dynamics in a two-dimensional van der Waals material and reveals several interesting phenomena that do not occur in bulk materials. Particularly, the focus will be two dynamic processes: carrier multiplication and ultrafast charge transfer.