title: Modification of the Highly Conductive PEDOT:PSS Layer for Use in Silver Nanogrid Electrodes for Flexible Inverted Polymer Solar Cells.
abstract: Silver nanogrid based flexible transparent electrode is recognized as the most promising alternative to ITO electrode for organic electronics, owing to its low production cost and excellent flexibility. Typically, a highly conductive thin film coating layer, such as highly conductive PEDOT:PSS (HC-PEDOT:PSS) is usually deposited onto the Ag-grid electrode to smooth the surface and to minimize the sheet resistance. In this paper, we found that inverted flexible polymer solar cells with structure of Ag-grid/HC-PEDOT:PSS/ZnO/photoactive layer/MoO3/Al generally exhibits strong S-shaped J-V curves, which could be eliminated by light-soaking treatment. Kelvin probe force microscope (KPFM) measurement proved that a large work function (WF) difference (0.70 eV) between HC-PEDOT:PSS and ZnO is the main reason for the formation of S-shape. White light soaking of the Ag-grid/HC-PEDOT:PSS gradually decreased the WF of HC-PEDOT:PSS from 5.10 to 4.60 eV, leading to a reduced WF difference between HC-PEDOT:PSS and ZnO from 0.70 to 0.38 eV. Such a WF difference decrease was believed to be the working mechanism for the light-soaking effect in this flexible device. Based on this finding, the HC-PEDOT:PSS solution was then modified by doping with polyethylenimine (PEI) and aqueous ammonia. The modified PEDOT:PSS film is characteristic of adjusting WF through varying PEI doping concentrations. By using such a modified PEDOT:PSS layer, light-soaking-free flexible inverted polymer solar cell with a power conversion efficiency of 6.58% was achieved for PTB7-Th:PC71BM cells. The current work provides a useful guideline for interfacial modification for Ag-grid based flexible electrode.
authors.affiliation: School of Electronic and Information Engineering, Xi'an Jiaotong University , Xi'an, Shanxi 710049, PR China.|Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Fei
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Qun
authors.identifier: http://orcid.org/0000-0002-7527-460X
authors.initials: Q
authors.lastname: Luo
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Shuhong
authors.initials: S
authors.lastname: Nie
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Na
authors.initials: N
authors.lastname: Wu
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Xiaolian
authors.initials: X
authors.lastname: Chen
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Wenming
authors.initials: W
authors.lastname: Su
authors.affiliation: School of Electronic and Information Engineering, Xi'an Jiaotong University , Xi'an, Shanxi 710049, PR China.
authors.forename: Yuanjie
authors.initials: Y
authors.lastname: Li
authors.affiliation: Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Collaborative Innovation Center of Suzhou Nano Science and Technology , Suzhou 215123, PR China.
authors.forename: Chang-Qi
authors.initials: CQ
authors.lastname: Ma
keywords: PEDOT:PSS/ZnO; flexible inverted organic solar cells; interfacial modification; light soaking; work function regulation