title: Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers.
abstract: Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor.
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Sankyuk-dong University Road 80, Daegu 702-701, Republic of Korea.|Blackett Laboratory, Department of Physics and Center for Plastic Electronics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Sungho
authors.initials: S
authors.lastname: Nam
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Sankyuk-dong University Road 80, Daegu 702-701, Republic of Korea.
authors.forename: Jooyeok
authors.initials: J
authors.lastname: Seo
authors.affiliation: Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Republic of Korea.
authors.forename: Sungho
authors.initials: S
authors.lastname: Woo
authors.affiliation: Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Republic of Korea.
authors.forename: Wook Hyun
authors.initials: WH
authors.lastname: Kim
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Sankyuk-dong University Road 80, Daegu 702-701, Republic of Korea.|Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Hwajeong
authors.initials: H
authors.lastname: Kim
authors.affiliation: Blackett Laboratory, Department of Physics and Center for Plastic Electronics, Imperial College London, London SW7 2AZ, UK.|Departments of Engineering Science and Physics, Division of Mathematical, Physical and Life Sciences, University of Oxford, Oxford OX1 3PD, UK.
authors.forename: Donal D C
authors.initials: DDC
authors.lastname: Bradley
authors.affiliation: Organic Nanoelectronics Laboratory, School of Applied Chemical Engineering, Kyungpook National University, Sankyuk-dong University Road 80, Daegu 702-701, Republic of Korea.
authors.forename: Youngkyoo
authors.identifier: http://orcid.org/0000-0002-9391-2636
authors.initials: Y
authors.lastname: Kim