title: Surface Modification of ZnO Layers via Hydrogen Plasma Treatment for Efficient Inverted Polymer Solar Cells.
abstract: Modifications of the ZnO electron extraction layer with low-pressure H plasma treatment increased the efficiency of inverted polymer solar cells (PSCs) based on four different photoactive blends, namely, poly(3-hexylthiophene):[6,6]-phenyl C71 butyric acid methyl ester (P3HT:PC71BM), P3HT:1',1″,4',4″-tetrahydro-di[1,4]methanonaphthaleno-[5,6]ullerene-C60 (P3HT:IC60BA), poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:PC71BM (PCDTBT:PC71BM), and (poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl]]):PC71BM (PTB7:PC71BM), irrespective of the donor:acceptor combination in the photoactive blend. The drastic improvement in device efficiency is dominantly attributable to the reduction in the work function of ZnO followed by a decreased energy barrier for electron extraction from fullerene acceptor. In addition, reduced recombination losses and improved nanomorphology of the photoactive blend in the devices with the H plasma treated ZnO layer were observed, whereas exciton dissociation also improved with hydrogen treatment. As a result, the inverted PSC consisting of the P3HT:PC71BM blend exhibited a high power conversion efficiency (PCE) of 4.4%, the one consisting of the P3HT:IC60BA blend exhibited a PCE of 6.6%, and our champion devices with the PCDTBT:PC71BM and PTB7:PC71BM blends reached high PCEs of 7.4 and 8.0%, respectively.
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Vasilis
authors.initials: V
authors.lastname: Papamakarios
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Ermioni
authors.initials: E
authors.lastname: Polydorou
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Soultati
authors.forename: Nikos
authors.initials: N
authors.lastname: Droseros
authors.forename: Dimitris
authors.initials: D
authors.lastname: Tsikritzis
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Antonios M
authors.initials: AM
authors.lastname: Douvas
authors.forename: Leonidas
authors.initials: L
authors.lastname: Palilis
authors.forename: Mihalis
authors.initials: M
authors.lastname: Fakis
authors.forename: Stella
authors.initials: S
authors.lastname: Kennou
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Argitis
authors.affiliation: Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos , 15310 Aghia Paraskevi Attikis, Athens Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Vasilopoulou
keywords: ZnO; charge generation efficiency; electron extraction; hydrogen plasma; polymer solar cells; reduced work function