title: Improving the conductivity of PEDOT:PSS hole transport layer in polymer solar cells via copper(II) bromide salt doping.
abstract: Copper(II) bromide (CuBr2) salt has been applied to dope poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL) in polymer solar cells (PSCs), improving dramatically the conductivity of PEDOT:PSS film and consequently the device power conversion efficiency (PCE). Under the optimized doping concentration of CuBr2 of 10 mmol·L(-1), PCE of the CuBr2:PEDOT:PSS HTL-incorporated BHJ-PSC device based on poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5- (4',7'-di-2-thienyl-2',1',3'- benzothiadiazole) (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) (PCDTBT:PC71BM) reaches 7.05%, which is improved by ∼20.7% compared to that of the reference device based on pristine PEDOT:PSS HTL (5.84%) and represents the highest PCE for PCDTBT:PC71BM-based PSC devices without an electron transport layer (ETL) reported so far. The dramatic improvement of the conductivity of PEDOT:PSS film is interpreted by the weakening of the Coulombic attractions between PEDOT and PSS components. The work function of CuBr2:PEDOT:PSS slightly increases compared to that of the undoped PEDOT:PSS as inferred from scanning Kelvin probe microscopy (SKPM) measurements, contributing to the improved PCE due to the increases of the open-current voltage (Voc) and fill factor (FF).
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China (USTC) , Hefei 230026, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhao
authors.forename: Qiliang
authors.initials: Q
authors.lastname: Wu
authors.forename: Fei
authors.initials: F
authors.lastname: Xia
authors.forename: Xiang
authors.initials: X
authors.lastname: Chen
authors.forename: Yawei
authors.initials: Y
authors.lastname: Liu
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Songyuan
authors.initials: S
authors.lastname: Dai
authors.forename: Shangfeng
authors.initials: S
authors.lastname: Yang
keywords: PEDOT:PSS; conductivity; copper bromide; hole transport layer; polymer solar cells