1 Air Force Research Laboratory Dr. Michael F. Durstock, , Device Architectures.. Aluminum ITO Glass V Electron Accepting Material Electron Donating Material Multilayer Architecture Layered structure with either polymeric or small-molecule materials. Interpenetrating Network Architecture Two phase system with each phase being percolated such that charge transport through each phase can occur. Active Components Electrolyte Semiconductor Particles Dye Michael Graetzel Dye-Sensitized Cell Hybrid between inorganic nanoparticles and organic dyes and electrolytes.

2 Air Force Research Laboratory Dr. Michael F. Durstock, , MDMO-PPV [6,6] PCBM Photoinduced Electron Transfer Carbon Nanofibers Incorporation of carbon nanofibers or nanotubes into photovoltaic device architectures – act as an aid to charge transport Poly(alkylthienylene vinylene) Broaden the spectral response of the devices by incorporating conjugated polymers with smaller bandgaps to absorb more of the lower energy solar radiation Discotic liquid crystals Conjugated systems that tend to stack into columnar domains and consequently have enhanced charge transport through the column Nano-templating Using porous anodic aluminum oxide (AAO) technology, control nanostructured morphology of the film for improved charge transport and device efficiency. Two component system used for heterojunction solar cells Organic Photovoltaics – Alternative Materials Systems Harris et. al., U. Akron

3 Air Force Research Laboratory Dr. Michael F. Durstock, , Broadening the Spectral Response Spectral response of materials in photovoltaic devices is narrow compared to the solar irradiance Variable bandgap materials allow more solar energy to be captured & converted to useful electrical energy Poly(thienylene vinylene)s are one class of materials that offer a lower bandgap while maintaining reasonable charge carrier mobilities and chemical stability Absorbance (Normalized) Absorbance Spectra Wavelength (nm) PPP PPV PTV Irradiance (W/m 2 /  m)

4 Air Force Research Laboratory Dr. Michael F. Durstock, , Current (  A) Active Layer Thickness (nm) (1:4 Donor to Acceptor) Voltage (V) Efficiency (%) Fill Factor Weight Percent PCBM Donor onlyAcceptor only Polymer Blend Device Characteristics

5 Air Force Research Laboratory Dr. Michael F. Durstock, , Polymer Blend Morphology 1:6 (PTV:PCBM) 1:2 (PTV:PCBM) 1:1 (PTV:PCBM) 1:3 (PTV:PCBM) 1:10 (PTV:PCBM) 1:4 (PTV:PCBM)

6 Air Force Research Laboratory Dr. Michael F. Durstock, , Potential templates J. Am. Chem. Soc., 1999, 121, Advantages:Regular interconnected network Controlled geometry Adv. Funct. Mater., 2003, 13,  m Anodic aluminum oxide –Easy fabrication –Variable pore length, diameter, interpore distance –Surface area not as high, but charge pathway direct Structure-directing block copolymers –Very high surface area –Pores on scale of exciton diffusion length, but too small? TiO 2 :P3HT – APL, 2003, 83, 3380.; Adv. Funct. Mater., 2003, 13, 301. Inverse opals –Well controlled void size,connecting pore diameter –Time consuming fabrication

7 Air Force Research Laboratory Dr. Michael F. Durstock, , Sensitized titania cell from anodic alumina Titania nanotubes/pillars from AAO – Sensitized with organic dye – Coated with semiconducting polymer – Possible continual layering – Easily modified surface chemistry Chem. Mater., 2002, 14 Electrochim. Acta, 2003, 48, Anatase nanotubes on ITO surface h e-e- e-e- e-e- redox Other geometries available…

8 Air Force Research Laboratory Dr. Michael F. Durstock, , 50 nm pores 150 nm pores TiO 2 nanotubules in nanoporous Al 2 O 3 Nanoporous Alumina Templating Nanoporous Al 2 O 3

9 Air Force Research Laboratory Dr. Michael F. Durstock, , Flexible Solar Power Niche AF Applications Enhanced, Flexible Solar Cells – Significantly reduced cost over current solar cell design – Enhanced efficiencies for more power. – Flexible, robust design permits portability. – Significantly reduced weight. Payoff to the Warfighter – Enabling technology for next- generation satellite systems. – Reduce logistical burden for Airbase deployment. – Provides special operations personnel with a source of renewable power in the theatre. – Enabling technology for high altitude airships.