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Konstantin Yamnitskiy, Yekaterina Shtyrkova, Palash Gangopadhyay, Jayan Thomas , Ramakrishna Voorakaranam, Robert A. Norwood and Nasser Peyghambarian College of Optical Sciences, University of Arizona • Improve efficiency in bulk heterojunction organic photovltaics (OPV) by enhancing charge collection during charge separation of electron hole pair, using magnetically polled semiconducting single wall carbon nano tubes as nano-pillars for increased area of interaction • Separate semiconducting from metallic nanotubes with ultracentrifugation • Break nanotubes into ~100nm segments • Assemble OPV's with nanotubes • Magnetically pole nanotubes to create oriented nano-pillars • Deposit electrodes • Perform I-V and efficiency characterization on devices Glass ITO PEDOT:PSS Aluminum I Light LiF Poly(3-hexylthiophene) (P3HT) Donor Acceptor [6,6]-phenyl C 61 butyric acid methyl ester (PCBM-60) • Increase area of interaction between donor and acceptor for better charge collection • Using SWCNT’s promotes better change transport to electrodes Anode Cathode Substrate Donor Acceptor e - h + e - h + e - h + e - e - SWCNT Electron collector electrode Hole collector electrode SEM showing cross section of polymer nanopillars with aligned SWCNT Aligned SWCNT M. S. ARNOLD et. al., NATURE 1, 60, (2006) Using density gradient ultracentrifugation in solution of 1:4 SDS/SC co- surfactants (sodium dodecyl sulfate (SDS), sodium cholate (SC)), semiconducting tubes are separated from metallic . Jie Liu et. al., SCIENCE 280, 1253, (1998) • Using a 3:1 mixture of sulfuric and nitric acid at 70°C , nanotubes can be shortened at rate of 100nm/hr • From 0.5-2 μm length tubes will be cut to ~100nm • Filtering can be used to select the proper size particles, suitable for incorporation in a ~ 100nm thick OPV • After spin coating the active layer with nanotubes included • Formed thin film is heated above T g • Poled and quenched to stabilize the nanotubes in the position perpendicular to substrate in the conjugated polymer: fullerene matrix S. Guines, et. al. Chem. Rev. 107, 1324 (2007)
