title: Enhanced performance in inverted polymer solar cells with D-π-A-type molecular dye incorporated on ZnO buffer layer.
abstract: We report the superior characteristics of a ZnO buffer layer covered with a phenothiazine-based, π-conjugated donor-acceptor (D-π-A)-type organic dye (called "d-ZnO"). The use of this system for the performance enhancement of inverted bulk heterojunction polymer solar cells (PSCs) with the configuration of indium tin oxide/d-ZnO/polymer:PC71 BM/MoO3 /Ag (PC71 BM=[6,6]-phenyl C71 butyric acid methyl ester) is investigated. The layer of organic dyes anchored on the ZnO surface through carboxylate bonding reduces the shunt path on bare ZnO surface and provides better interfacial contacts and energy level alignments between the ZnO layer and the photoactive layer. This phenomenon consequently leads to highly enhanced photovoltaic parameters (fill factor, open-circuit voltage, and short-circuit current density) and power conversion efficiencies (PCEs). Inverted solar cells containing the d-ZnO layer not only revealed about 34% (PCE: 4.37%) and 18% (PCE: 7.11%) improvement in the PCEs of the representative poly-3(hexylthiophene) (P3HT) and low-band-gap poly{[4,8-bis-(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-alt-[2-(2'-ethylhexanoyl)-thieno[3,4-b]thiophen-4,6-diyl]} (PBDTTT-C-T) polymer systems, respectively, but also showed 2-4 times longer device lifetimes than their counterparts without the organic dye layer. These results demonstrate that this simple approach used in inverted PSCs with a metal oxide buffer layer could become a promising procedure to fabricate highly efficient and stable PSCs.
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science & Technology (KAIST), Daejeon, 305-701, Republic of Korea.
authors.forename: Chang Eun
authors.initials: CE
authors.lastname: Song
authors.forename: Ka Yeon
authors.initials: KY
authors.lastname: Ryu
authors.forename: Seong-Jin
authors.initials: SJ
authors.lastname: Hong
authors.forename: Chinna
authors.initials: C
authors.lastname: Bathula
authors.forename: Sang Kyu
authors.initials: SK
authors.lastname: Lee
authors.forename: Won Suk
authors.initials: WS
authors.lastname: Shin
authors.forename: Jong-Cheol
authors.initials: JC
authors.lastname: Lee
authors.forename: Si Kyung
authors.initials: SK
authors.lastname: Choi
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Moon
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D002021:Buffers; D003487:Cyanoacrylates / Q000737:chemistry*; D011211:Electric Power Supplies; D004566:Electrodes; D008958:Models, Molecular; D008968:Molecular Conformation; D010640:Phenothiazines / Q000737:chemistry*; D012993:Solar Energy; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: C586888:2-cyano-3-(7-(4-(diphenylamino)phenyl)-10-hexyl-10H-phenothiazine-3-yl)acrylic acid; D000179:Acrylates; D002021:Buffers; D003487:Cyanoacrylates; D010640:Phenothiazines; C036658:acrylic acid; D015034:Zinc Oxide
keywords: bulk heterojunction; electro-optical materials; photovoltaic devices; surface modification; zinc oxide