Since the use of fossil fuels has caused environmental pollution problems, scientists have been searching for alternative clean energy sources, which include conversion of solar energy to electricity. Silicon-based solar cells have been the mainstream, but their price is still high compared to fossil fuel energy generation. Therefore, next generation solar cells fabricated with higher efficiency, cheaper materials, and low manufacturing cost need to be created. With these proposed criteria, dye-sensitized solar cells (DSSCs) and plasmon-induced hot electron solar cells were studied and are described in this dissertation.

For the fabricated DSSCs, graphitic carbon nitride (g-CN) was utilized as an inexpensive and efficient counter electrode catalyst replacing the expensive conventional platinum for standard DSSCs using a triiodide/iodide redox couple, an N719 dye, and FTO glass substrates. In spite of its versatile applicability thanks to the intrinsic semiconducting property and the electron-rich nitrogen surface functionality, g-CN has never been employed as an electrocatalyst in DSSCs, possibly due to its inferior electrical conductivity. In order to address this problem, a conductive material was deposited along with the g-CN onto the cathode and a sacrificial binder was used to ensure homogeneous coating of g-CN and the conductive material. When electrocatalytic performance was investigated by electrochemical impedance spectroscopy (EIS) on symmetric dummy cells, the charge transfer resistance (Rct) was found to decrease with a higher content of g-CN confirming its superior conductivity and potential catalytic activity. DSSCs with the g-CN catalyst on the counter electrodes exhibited good power conversion efficiencies comparable to that of Pt.

For the plasmon-induced hot electron solar cells, a wholly plasmonic photovoltaic device in which photon absorption and carrier generation take place exclusively in the plasmonic metal was fabricated. Energetic 'hot' electrons resulting from the decay of excited plasmons were extracted using a Schottky barrier to produce the output photocurrent. Its wavelength response tracks the absorption spectrum of the transverse plasmon of the gold nanorods indicating that the absorbed photon-to-electron conversion process was exclusively associated with the Au.

The aforementioned solid-state plasmonic solar cell was able to generate power with a respectable absorbed photon-to-electron conversion efficiency; however, high power conversion efficiency was not achievable with a thin TiO 2 layer most likely because of dielectric breakdown. In order to solve this problem, a liquid-junction using a redox electrolyte was employed between the two electrodes. The use of this liquid-junction greatly reduced the dielectric breakdown in the oxide layers that were utilized, leading to a great improvement in the long-term stability of the cell's performance.