Journal
NANO LETTERS
Volume 18, Issue 1, Pages 109-116Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b03540
Keywords
Charge separation; plasmon-exciton coupling; electron donor; electron acceptor; Kelvin probe force microscopy; surface potential image
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Funding
- Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education, Science and Technology [NRF-2015R1A1A1A05027681, NRF-2016K1A3A1A32913212]
- AOARD [FA2386-13-1-4124]
- Vannevar Bush Faculty Fellowship program - Basic Research Office of the Assistant Secretary of Defense for Research and Engineering
- Office of Naval Research [N00014-15-1-0043]
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Plasmon-induced interfacial charge separation (PICS) is one of the key processes responsible for the improved conversion efficiencies of energy-harvesting devices that incorporate metal nanostructures. In this Letter, we reveal a mechanism of PICS by visualizing (with nanometer-scale resolution) and characterizing plasmonexciton coupling between p-type poly(pyrrole) (PPy) nanowires (NWs) and Ag nanoparticles (NPs) using light-irradiated Kelvin probe force microscopy (KPFM). Under blue-light irradiation, the Ag NPs are expected to donate electrons to the PPy NWs via a hot electron injection process. However, in this Letter, we observe that under blue-light irradiation the plasmonically and excitonically excited electrons in the semiconductor back-transfer to the metal. The PICS in this system can be explained by comparing it with a similar one where Au NPs are attached to n-type ZnO NWs; we observed a net electron transfer from the Au NPs to the ZnO NWs (an upward band bending is formed at the interface of the two materials, presumably obstructing electron back-transfer). Indeed, energy band matching between the metal and the semiconductor components of hybrid nanostructures influences PICS pathways. These experimental findings and our proposed mechanism consistently explain the PICS occurring in the PPy NW-Ag NP system with important implications on explaining their cooperative optoelectronic activities.
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