Enhancing  the Photovoltaic Performance of Dye-Sensitized Solar Cells with Rare-Earth Metal Oxide Nanoparticles

Wednesday, 4 October 2017: 12:00
National Harbor 9 (Gaylord National Resort and Convention Center)
F. P. Zamborini, B. W. Alphenaar, and P. L. Kharel (University of Louisville)
Dye-sensitized solar cells consist of a photoanode of a mesoporous film of titania sensitized with dye sandwiched with a counter electrode, which is usually a platinum-coated transparent conducting oxide, and a redox couple injected between the photoanode and counter electrode. Doping titania with rare-earth metals has been an interesting approach to improve the conversion efficiency of dye sensitized solar cells. Rare-earth metals have been doped into titania paste to show an improvement in the photovoltaic performance of dye-sensitized solar cells, however, most of the reported cells are not efficient enough to conclude whether the enhancement is due to doping or it is because of the cell quality. We incorporated nanoparticles (<100 nm) of oxides of rare-earth metal (neodymium and erbium) in titania paste and built dye-sensitized solar cells using amphiphilic C101 dye and nitrile based iodide/triiodide redox couple, Z960 electrolyte. The doping level for optimized cells was 2.0 % for neodymium oxide and 1.0 % for erbium oxide. Our cells exhibit efficiencies more than 10 % and the best erbium oxide doped cell displayed an efficiency above 11 %. We measured the photocurrent, impedance, IPCE, dye loading, and film conductivity to investigate the enhancement of the photovoltaic performace by rare-earth metal oxides. Electrochemical impedance spectroscopy (EIS) measurements showed that doping with rare-earth metals decreased the total impedance of the cell and IPCE measurements revealed enhanced photon absorption by the dye in rare-earth metal doped cells. In the same fashion, the rare-earth metal -doped anodes showed larger dye loading compared to undoped anodes, which was maximum for 1.0 % doping of erbium oxide and 2.0 % doping of neodymium oxide. Rare earth metal oxides not only enhance dye adsorption but also facilitate electron tranport through the mesoporous layer, thereby increasing the collection efficiency of the photoexcited electrons.