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Efficient Organic Excitonic Solar Cells with Carbon Nanotubes Replacing In2O3:Sn as the Transparent Electrode (Presentation)

Description: The conclusions of this report are that: (1) organic solar cells with efficiencies of up to 1.43% conversion efficiency that use no ITO and no PEDOT:PSS, are demonstrated; (2) a cell without ITO, but with PEDOT:PSS gave 2.6% conversion efficiency; (3) due to porous nature of SWCNT substrates, optimization of the active layer is essential; and (4) SWCNT electrodes bring one step closer the goal of a fully printable, organic solar cell.
Date: May 1, 2006
Creator: van de Lagemaat, J.; Barnes, T.; Rumbles, G.; Shaheen, S.; Coutts, T. J.; Weeks, C. et al.
Partner: UNT Libraries Government Documents Department

Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint

Description: We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission properties of these coatings are presented in relation to their electrical properties (sheet resistance), along with preliminary solar cell results from devices made using CuIn1-xGaxSe2 thin-film absorber materials. Achieving an energy conversion efficiency of >12% and a quantum efficiency of {approx}80% demonstrate the feasibility of the concept. A discussion of the device structures will be presented considering the physical properties of the new electrodes comparing current-voltage results from the new solar cell structure and those from standard ZnO/CdS/Cu(In,Ga)Se2/Mo solar cells.
Date: May 1, 2006
Creator: Contreras, M.; Barnes, T.; van de Lagemaat, J.; Rumbles, G.; Coutts, T. J.; Weeks, C. et al.
Partner: UNT Libraries Government Documents Department

Bulk Heterojunction Organic Photovoltaic Devices Using Dendrimers

Description: A family of prototype ..pi..-conjugated dendrimers has been synthesized and incorporated into solution-processable organic photovoltaic (OPV) devices. Bulk heterojunction devices were fabricated by blending the dendrimers with a solubilized fullerene. The best of these initial devices, which were not optimized for morphology, exhibited external quantum efficiencies of 22% at peak wavelength. It was found that 3-arm dendrimers, when sufficiently soluble, yielded higher photocurrents than their 4-arm counterparts. This was attributed to better planarity and intermolecular alignment of the 3-arm version. Device efficiency was seen to increase with increasing arm length. A reduced-band gap dendrimer was synthesized by attaching electron-withdrawing groups onto the core to yield an optical band gap of 1.82 eV.
Date: November 1, 2005
Creator: Kopidakis, N.; Mitchell, W. J.; Bozell, J. J.; Piris, J.; Ginley, D. S.; Rumbles, G. et al.
Partner: UNT Libraries Government Documents Department

Short-Term Metal/Organic Interface Stability Investigations of Organic Photovoltaic Devices: Preprint

Description: This paper addresses one source of degradation in OPV devices: the metal/organic interface. The basic approach was to study the completed device stability vs. the stability of the organic film itself as shown in subsequent devices fabricated from the films.
Date: May 1, 2008
Creator: Reese, M. O.; Morfa, A. J.; White, M. S.; Kopidakis, N.; Shaheen, S. E.; Rumbles, G. et al.
Partner: UNT Libraries Government Documents Department

Polymer Based Nanocomposites for Solar Energy Conversion

Description: Organic semiconductor-based photovoltaic devices offer the promise of low cost photovoltaic technology that can be manufactured via large-scale, roll-to-roll printing techniques. Existing organic photovoltaic devices are currently limited to solar power conversion efficiencies of 3?5%. This is because of poor overlap between the absorption spectrum of the organic chromophores and the solar spectrum, non-ideal band alignment between the donor and acceptor species, and low charge carrier mobilities. To address these issues, we are investigating the development of dendrimeric organic semiconductors that are readily synthesized with high purity. They also benefit from optoelectronic properties, such as band gap and band positions, which can be easily tuned by substituting different chemical groups into the molecule. Additionally, we are developing nanostructured oxide/conjugated polymer composite photovoltaics. These composites take advantage of the high electron mobilities attainable in oxide semiconductors and can be fabricated using low-temperature solution-based growth techniques. Here, we discuss the synthesis and preliminary device results of these novel materials and composites.
Date: January 1, 2005
Creator: Shaheen, S.; Olson, D.; White, M.; Mitchell, W.; Miedaner, A.; Curtis, C. et al.
Partner: UNT Libraries Government Documents Department