A synthetic approach has been developed which results in CuInS quantum dots (QDs) possessing localized surface plasmon resonance (LSPR) modes in the near infrared (NIR) frequencies. Importantly, these LSPRs stem from native cation vacancies acting as acceptor sites as determined through Rutherford backscattering spectroscopy (RBS), rather than being born of gradual oxidative leeching effects post-crystal formation. This renders the LSPRs synthetically tunable, as well as stable over many weeks of storage. In order to investigate the hypothetical benefits of near-field plasmonic effects centered upon photovoltaic absorber material, non-plasmonic counterparts (“twins”) were developed based on a modified literature method as an experimental control. Scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) mapping, absorption spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy were used to verify the nearly identical nature of the species of Cu-In-S-containing QDs, differing only in their stoichiometries. Simple QD-sensitized solar cells (QD-SSCs) were assembled which show an 11.5% average increase in incident photon conversion efficiency (IPCE) in the plasmon-enhanced devices with respect to the non-plasmonic controls. We attribute this bolstering of performance to augmented absorption stemming from near-field “antenna” effects in the plasmonic CuInS QD-SSCs. This study represents the first of its kind: direct interrogation of the influence of plasmon-on-semiconductor architectures on IPCE in photovoltaic systems.
Vanderbilt University, Vanderbilt Institute for Nanoscale Science and Engineering
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