Role of the Metal Oxide Electron Acceptor on Gold–Plasmon Hot-Carrier Dynamics and Its Implication to Photocatalysis and Photovoltaics

Abstract

The recent discovery that metal nanoparticles can generate hot carriers upon light excitation is seen as a breakthrough in the fields of plasmonics and photonics. However, the high expectations for a plasmonic revolution in applications have been dampened by the ultrafast energy dissipation of surface plasmon polariton modes. While research aimed at suppressing loss mechanisms is still pursued, another research direction has emerged where charges are harnessed before they relax. Despite the effort, efficiencies of devices based on hot carriers harnessed from plasmonics are typically very low (a few percent), which is somehow paradoxical since efficiencies for electron injection efficiency have been reported to be in the range from 25% to 40% and hole injection up to 85%. This indicates that the low device performance relates to the undesirable charge back-transfer process, which happens in the picosecond time scale. In this context, we performed a comparative ultrafast spectroscopy investigation with gold nanoparticles in direct contact with different metal oxides, namely, TiO2, ZnO, SnO2, and Al:ZnO. Electron dynamics revealed the decisive role of metal/semiconductor interfaces and semiconductor electronic structure in electron injection efficiency and recombination, with significant implications to the fields of photocatalysis and photovoltaics.

Photophysical Study of Electron and Hole Trapping in TiO2 and TiO2/Au Nanoparticles through a Selective Electron Injection

“…By calculating the time difference between the rising signal and the signal of cross-section modulation (the inset of Figure b), it was found that the injection time from the pulse arriving to an electron reaching the bottom of the conduction band is around 0.6 ps in this TiO 2 /Au NPs system. Before, we studied the injection of the hot electrons in several metal oxide/Au NPs systems and found that the injection time of electrons from Au NPs to TiO 2 is <0.1 ps. , The extra time (∼0.5 ps) the photogenerated electrons spend to arrive at the bottom of the conduction band could result from the diffusion time of the carrier in Au NPs to the interface between Au NPs and TiO 2 , and this time shall be related to the size of the Au NPs.…”

“…Before, we studied the injection of the hot electrons in several metal oxide/Au NPs systems and found that the injection time of electrons from Au NPs to TiO 2 is <0.1 ps. 44,45 The extra time (∼0.5 ps) the photogenerated electrons spend to arrive at the bottom of the conduction band could result from the diffusion time of the carrier in Au NPs to the interface between Au NPs and TiO 2 , and this time shall be related to the size of the Au NPs. However, it is still not well understood the process of electron injection from Au NPs into TiO 2 and the electron depopulation process after injection.…”

A surface plasmon polariton-triggered Z-scheme for overall water splitting and solely light-induced hydrogen generation

“…The utilization of the plasmon triggering of the semiconductor material photo/electrochemical catalytic activity has been widely reported. [54][55][56] Commonly, the enhancement of catalytic activity occurs due to the plasmon-assisted injection of hot electrons or holes in the semiconductor, enhancement of electron-hole pair generation inside the semiconductor, and the acceleration of charge carrier migration and separation. 57,58 Most of these events have been reported for the combination of a single semiconductor with plasmonic structures, but there are just several similar reports for the Z-scheme design combined with plasmon-active noble metal nanostructures.…”

Plasmon Mediated Electron Transfer and Temperature Dependent Electron‐Phonon Scattering in Gold Nanoparticles Embedded in Dielectric Films

“…After generating plasmonic hot-electron, transportation to the adjacent semiconductor depends on the interfacial Schottky barrier height. [12,16,17] Jiang and co-workers reported that the photocatalytic activity of SnO 2 increases, when the metal Ag NPs are deposited on the semiconductor surface. [18] It has been recognized that direct contact between the metal and semiconductor sub-system can enhance the HET from metal NPs to the conduction band of the TiO 2 .…”

“…Plasmonic nanostructure can be directly convert the incident light energy to electrical energy by generating hot‐electron and transporting it to suitable SC. After generating plasmonic hot‐electron, transportation to the adjacent semiconductor depends on the interfacial Schottky barrier height [12,16,17] . Jiang and co‐workers reported that the photocatalytic activity of SnO 2 increases, when the metal Ag NPs are deposited on the semiconductor surface [18] .…”