Optical Field Coupling in ZnO Nanorods Decorated with Silver Plasmonic Nanoparticles.

Characterizing carrier redistribution due to optical field modulation in a plasmonic hot-electron/semiconductor junction can raise the framework for harnessing the carrier decay of plasmonic metals in more efficient conversion systems. In this work we comprehensively studied the carrier redistribution mechanisms of a 1-dimensional (1D) metal-semiconductor Schottky architecture, holding the dual feature as a hot-electron plasmonic system and a simple metal/semiconductor junction. We obtained strongly enhanced external quantum efficiency (EQE) of the plasmonic Ag decorated ZnO semiconductor in both band-edge region of ZnO and the corresponding plasmonic absorption profile of the Ag NPs (visible region). Simultaneously, insertion of an insulating Al2O3 intermediate layer between Ag NPs and ZnO, resulted in a parallel distinction of the two main non-radiative carrier transfer mechanisms of plasmonic NPs, i.e. direct electron transfer (DET) and plasmonic induced resonance energy transfer (PIRET). The multi-wavelength transient pump-probe spectroscopy indicated the very fast plasmonic radiative transfer dynamics of the system in <500fs below 389nm. We demonstrate the 13% increase of photogenerated current in ZnO upon visible irradiation as a result of non-radiative plasmonic hot-electron injection from Ag NPs. Overall, our device encompasses several effective solution for designing a plasmonic system featuring non-radiative electron-electron plasmonic dephasing and high photoconversion efficiencies.