title: Niobium Doping Effects on TiO2 Mesoscopic Electron Transport Layer-Based Perovskite Solar Cells.
abstract: Perovskite solar cells (PSCs) are the most promising candidates as next-generation solar energy conversion systems. To design a highly efficient PSC, understanding electronic properties of mesoporous metal oxides is essential. Herein, we explore the effect of Nb doping of TiO2 on electronic structure and photovoltaic properties of PSCs. Light Nb doping (0.5 and 1.0 at %) increased the optical band gap slightly, but heavy doping (5.0 at %) distinctively decreased it. The relative Fermi level position of the conduction band is similar for the lightly Nb-doped TiO2 (NTO) and the undoped TiO2 whereas that of the heavy doped NTO decreased by as much as ∼0.3 eV. The lightly doped NTO-based PSCs exhibit 10 % higher efficiency than PSCs based on undoped TiO2 (from 12.2 % to 13.4 %) and 52 % higher than the PSCs utilizing heavy doped NTO (from 8.8 % to 13.4 %), which is attributed to fast electron injection/transport and preserved electron lifetime, verified by transient photocurrent decay and impedance studies.
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea).
authors.forename: Dong Hoe
authors.initials: DH
authors.lastname: Kim
authors.affiliation: School of Advanced Materials Science&Engineering, Sungkyunkwan University, Suwon 440-746 (Korea).
authors.forename: Gill Sang
authors.initials: GS
authors.lastname: Han
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea).
authors.forename: Won Mo
authors.initials: WM
authors.lastname: Seong
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea).
authors.forename: Jin-Wook
authors.initials: JW
authors.lastname: Lee
authors.affiliation: School of Advanced Materials Science&Engineering, Sungkyunkwan University, Suwon 440-746 (Korea).
authors.forename: Byeong Jo
authors.initials: BJ
authors.lastname: Kim
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea).
authors.forename: Nam-Gyu
authors.initials: NG
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea).
authors.forename: Kug Sun
authors.initials: KS
authors.lastname: Hong
authors.affiliation: Department of Materials Science and Engineering, University of California at Berkeley, CA 94720 (USA). wook2@berkeley.edu.
authors.forename: Sangwook
authors.initials: S
authors.lastname: Lee
authors.affiliation: School of Advanced Materials Science&Engineering, Sungkyunkwan University, Suwon 440-746 (Korea). hsjung1@skku.edu.
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jung
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D011211:Electric Power Supplies; D004579:Electron Transport; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012993:Solar Energy; D014025:Titanium / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D009556:Niobium; C059910:perovskite; C009495:titanium dioxide; D014025:Titanium
keywords: anatase; electronic structure; niobium; perovskite; solar cells