Routes to Improved Light Harvesting in Thin Film Photoelectrochemical Devices: Examining Nanoscale Light Absorbers at the Metal Oxide Interface

The continuous increase in energy demand is forcing our society to search for environmentally clean and sustainable energy sources, of which solar energy is of prominent interest. Efficient conversion of sunlight to electricity and storable fuels is a compelling challenge for modern science. Dye-sensitized solar cells (DSSCs) have received considerable attention as a cost-effective technology for light-to-electrical energy conversion. Improvements in device efficiency, however, are necessary in order to realize widespread implementation.;One pathway toward improved efficiency is photocurrent enhancement through increased light harvesting. The incorporation of silver nanoparticles (Ag NPs) into planar, DSSC photoelectrodes has afforded enhanced performance through amplification of light absorption of the dye sensitizer through localized surface plasmon resonance (LSPR). To explore the fundamental properties of this architecture, various metal oxide thin films, grown by atomic layer deposition (ALD), were employed to investigate the influence of dielectric environment on photocurrent enhancement in DSSCs containing Ag NPs supporting LSPR.;The same planar architecture was used to evaluate plasmonic enhancement of cadmium selenide (CdSe) quantum dots (QDs), which exhibit superior light absorption relative to dye molecules. The enhancement effect was observed to sustain the exciton lifetimes in QDs and to strongly depend on the incident photon wavelength following the plasmon resonant strength of Ag NPs, confirming that the enhanced photoluminescence was mainly due to the enhancement in photon absorption (light harvesting) in CdSe QDs by the plasmon of Ag NPs. The calculated fluorescence enhancement factors suggest that a unique combination of nanostructured metal and quantum-confined semiconductors are a promising route to increasing light harvesting in photoelectrochemical (PEC) devices.;The conversion of sunlight to hydrogen by means of photocatalysis is one of the most interesting ways to achieve storable, renewable energy. In order to potentially address stability issues involving hole corrosion of CdSe in PEC devices, ultrathin hole-conducting NiO films made by ALD were characterized using the oxygen evolution reaction and investigated as a prospective hole scavenger in semiconductor-semiconductor photocatalytic systems for the reduction of water. The effect of the surface linker structure on hole transfer times from the QD to NiO was examined using time-resolved fluorescence spectroscopy.