Carrier depletion mediated exciton-surface plasmon coupling at the mesoporous TiO2/Ag interface

Abstract

We systematically investigated the effect of the change in the carrier depletion width in the TiO2 on the exciton-plasmon coupling at the TiO2/Ag nanoparticle (NP) interface, excluding complications associated with the optical and electrochemical screening of Ag NPs. We found that Ag NP-induced interfacial traps are coupled with the energy band bending in the TiO2 under illumination, suppressing plasmon-induced interfacial charge separation at the TiO2/Ag NP interface. Under illumination with solar simulator including UV, reduction in the depletion width of the TiO2 facilitated back-transfer of the excited electrons in the TiO2 to Ag NP-induced interfacial localized states, while green light irradiation enhanced the photocurrent by plasmonic-induced charge separation. Surface potential change depending on light irradiation is discussed relating to exciton-plasmon coupling at the TiO2/Ag NP interface combined with Mott-Schottky analysis. For the first time, we distinguished the optical and electrochemical screening by the plasmonic nanostructure from carrier depletion-induced band bending at the TiO2/Ag NP interface. We demonstrated the significant effect of the localized interfacial states and the energy band bending on the exciton-plasmon coupling. © 2021 Elsevier B.V.