Design, fabrication, and optimization of plasmonic materials for application in dye-sensitized solar cells.

摘要

Dye-sensitized solar cells (DSSCs) comprise a promising light-to-electrical energy conversion technology due to their ease and economy of fabrication. However, the efficiencies of these cells in their standard configuration suffer from losses in voltage due to the large overpotential required to drive the regeneration of the dye by the kinetically slow I-/I 3- redox shuttle. Flat electrodes would enable the use of alternative, kinetically fast redox shuttles, which give rise to prohibitively large dark currents in standard anodes, but they also harvest less light due to reduced dye loading. Losses in light absorption can be partially addressed by implementing plasmonic materials in DSSC photoanodes; the enhanced electromagnetic field near the plasmonic particles can lead to enhanced absorption by the dye.;The work in this thesis explores the design, fabrication, and implementation of plasmonic materials in DSSCs. Atomic layer deposition (ALD) was used to fabricate a conformal layer of TiO2 to protect the plasmonic materials from the corrosive redox shuttle. The thickness of the TiO2 layer between the plasmonic nanoparticles (NPs) and the dye was systematically varied, and the observed plasmon enhancement factor decreased as the spacing between the NPs and the dye increased.;Mie theory was used to computationally reproduce the distance-dependent decay in plasmonic enhancement. Qualitative agreement with the experimental results was obtained. However, the experimental systems were too disordered to accurately model, and quantitative agreement between calculations and experiments was not achieved.;Silver films with structured arrays of cross-shaped holes were subsequently explored, with the aid of finite-difference time-domain (FDTD) calculations, as potential plasmonic anodes. It was observed that a prohibitively thick layer of TiO2 is required to protect the films from corrosion. The FDTD calculations reproduce the features in the extinction spectra, but the calculated peaks are red-shifted relative to the experimental peaks.;Finally, the solar cell performance parameters were compared for flat, plasmonic anodes and high-area, mesoporous anodes with a variety of redox shuttles. The flat solar cells exhibited reduced dark current with all of the redox shuttles, but neither the diode equation or the ideal diode equation could accurately quantify the reduction in dark current.