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NREL Improves Hole Transport in Sensitized CdS-NiO Nanoparticle Photocathodes (Fact Sheet)

Description: Significantly improved charge-collection efficiencies result from a general chemical approach to synthesizing photocathodes. It has been reported that a dye-sensitized nickel oxide (NiO) photocathode, when coupled to a dye-sensitized photoanode, could significantly increase overall solar conversion efficiency. However, the conversion efficiencies of these cells are still low. There has been much effort to improve the conversion efficiency by fabricating films with improved properties and developing more effective sensitizing dyes for p-type NiO. One of the factors limiting the use of NiO for solar cell application is the low hole conductivity in p-NiO. A team of researchers from the National Renewable Energy Laboratory (NREL) developed a general chemical approach to synthesize NiO-cadmium sulfide (CdS) core-shell nanoparticle films as photocathodes for p-type semiconductor-sensitized solar cells. Compared to dye-sensitized NiO photocathodes, the CdS-sensitized NiO cathodes exhibited two orders of magnitude faster hole transport (attributable to the passivation of surface traps by the CdS) and almost 100% charge-collection efficiencies.
Date: January 1, 2012
Partner: UNT Libraries Government Documents Department

Fabrication of High Current YBa<sub>2</sub>Cu<sub>3</sub>O(sub>7-y</sub>) Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates

Description: High critical current YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-y</sub> (referred to as YBCO) coated conductors were fabricated with a layer sequence of YBCO/YSZ/CeO<sub>2</sub>/Ni. The cube (100) texture in the starting Ni substrates was obtained by cold rolling followed by recrystallization. A thin CeO<sub>2</sub> (Cerium Oxide) layer with a thickness of 100-200 Å was grown epitaxially on the biaxially textured-Ni substrates using an e-beam evaporation technique. This was followed by the growth of a thick (<= 0.77 µm) YSZ (Yttria Stabilized Zirconia) layer using either e-beam evaporation or rf magnetron sputtering. The e-beam CeO<sub>2</sub> film had a dense microstructure. The microstructure of the e-beam YSZ film was porous whereas the sputtered YSZ film was dense. The YBCO films were grown by pulsed laser deposition on both e-beam and sputtered YSZ layers. A transport critical current density of ~ 1 x l0<sup>6</sup> A/cm<sup>2</sup> at 77 K was obtained for ~ 0.8 µm thick YBCO Rims on both YSZ surfaces in zero field. To demonstrate the quality and compatibility of the e-beam CeO<sub>2</sub> layers; YBCO films were also grown on CeO<sub>2</sub>-buffered YSZ (100) single crystal substrates using e-beam co-evaporated Y-BaF<sub>2</sub>-Cu precursors followed by a post-annealing process. A transport critical current density of over 1 x lO<sup>6</sup>A/cm<sup>2</sup> at 77 K was obtained on a ~ 0.3 µm thick YBCO film in zero field.
Date: June 1, 1999
Creator: Christen, D.K.; Feenstra, R.; Kroeger, D.M.; Lee, D.F.; List, F.A.; Martin, P.M. et al.
Partner: UNT Libraries Government Documents Department