title: Self-assembled hybrid polymer-TiO2 nanotube array heterojunction solar cells.
abstract: Films comprised of 4 microm long titanium dioxide nanotube arrays were fabricated by anodizing Ti foils in an ethylene glycol based electrolyte. A carboxylated polythiophene derivative was self-assembled onto the TiO2 nanotube arrays by immersing them in a solution of the polymer. The binding sites of the carboxylate moiety along the polymer chain provide multiple anchoring sites to the substrate, making for a stable rugged film. Backside illuminated liquid junction solar cells based on TiO2 nanotube films sensitized by the self-assembled polymeric layer showed a short-circuit current density of 5.5 mA cm-2, a 0.7 V open circuit potential, and a 0.55 fill factor yielding power conversion efficiencies of 2.1% under AM 1.5 sun. A backside illuminated single heterojunction solid state solar cell using the same self-assembled polymer was demonstrated and yielded a photocurrent density as high as 2.0 mA cm-2. When a double heterojunction was formed by infiltrating a blend of poly(3-hexylthiophene) (P3HT) and C60-methanofullerene into the self-assembled polymer coated nanotube arrays, a photocurrent as high as 6.5 mA cm-2 was obtained under AM 1.5 sun with a corresponding efficiency of 1%. The photocurrent action spectra showed a maximum incident photon-to-electron conversion efficiency (IPCE) of 53% for the liquid junction cells and 25% for the single heterojunction solid state solar cells.
authors.affiliation: Department of Electrical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Karthik
authors.initials: K
authors.lastname: Shankar
authors.forename: Gopal K
authors.initials: GK
authors.lastname: Mor
authors.forename: Haripriya E
authors.initials: HE
authors.lastname: Prakasam
authors.forename: Oomman K
authors.initials: OK
authors.lastname: Varghese
authors.forename: Craig A
authors.initials: CA
authors.lastname: Grimes
mesh_terms: D004563:Electrochemistry; D004573:Electrolytes / Q000737:chemistry; D019855:Ethylene Glycol / Q000737:chemistry; D037741:Fullerenes / Q000737:chemistry; D018625:Microscopy, Atomic Force; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000528:radiation effects; D010777:Photochemistry; D012993:Solar Energy; D012996:Solutions / Q000737:chemistry; D013057:Spectrum Analysis; D013499:Surface Properties; D013876:Thiophenes / Q000737:chemistry*; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D004573:Electrolytes; D037741:Fullerenes; D012996:Solutions; D013876:Thiophenes; C507295:poly(3-hexylthiophene); C009495:titanium dioxide; D014025:Titanium; D019855:Ethylene Glycol; C069837:fullerene C60