Photoinduced Hot Carrier Transfer in Tin-Doped Indium Oxide Nanocrystals

Doped semiconductor nanocrystals support tunable localized surface plasmon resonances with strong optical absorption cross sections and band gaps. However, unlike their coinage metal counterparts, semiconductor nanocrystals often have much lower carrier concentrations. Upon excitation, these materials produce non-equilibrium carrier distributions that rapidly relax, presenting a brief window for use. These features mark plasmonic nanocrystals as promising candidates for new applications that require efficient light absorption and highly directed energy and carrier utilization, such as photodetectors, photovoltaics, and photocatalysts, if we can understand and engineer efficient transport mechanisms. Here, we investigate hot carrier and heat transfer from prototypical tin-doped indium oxide (ITO) nanocrystals to adsorbates as a model system for harvesting and utilizing light in plasmonic semiconductor nanocrystals. Using transient absorption spectroscopy, we track carrier and energy transfer from ITO nanocrystals to adsorbates and evaluate the impact of aliovalent dopant concentration, wavelength, and energy level alignment. We find that the low carrier concentration in ITO enables new pathways to direct energy from light and that these variables strongly impact carrier transfer to adsorbates. Combining these results, we suggest general design rules to optimize carrier and energy transfer from plasmonic semiconductors. In addition, we demonstrate these rules in new devices leveraging these new transport processes.