title: Well-defined star-shaped conjugated macroelectrolytes as efficient electron-collecting interlayer for inverted polymer solar cells.
abstract: A star-shaped monodisperse conjugated macroelectrolyte grafted with cationic side chains, TrNBr, was designed, synthesized, and utilized as efficient electron-collecting cathode interlayers for inverted polymer solar cells. A neutral one composed of identical star-shaped conjugated backbone, TrOH, was also investigated for comparison. The surface properties and the function as interfacial layers on modulating the work function of bottom electrode (indium tin oxide) were systematically studied. Both interfacial electron-selective materials show strongly thickness-dependent performance for inverted polymer solar cells, and the best performance could be achieved via optimizing the thickness with 2.4 nm of TrNBr and 8.7 nm of TrOH. Parallel investigations of optimized TrNBr and TrOH interlayer in inverted architecture with active blend layer of poly(3-hexylthiophene):indene-C60 bisadduct (P3HT:ICBA) demonstrated a remarkable power conversion efficiency (PCE) enhancement (PCE of 4.88% for TrNBr and 4.74% for TrOH) in comparison with those of conventional noninverted devices using Ca/Al cathodes (3.94%) and inverted devices with sol-gel ZnO buffer layer (4.21%). In addition, the inverted devices using the TrNBr and TrOH interlayer exhibited improved device stability in contrast to conventional noninverted devices using Ca/Al cathodes.
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials(IAM), Jiangsu National Synergistic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications , 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Xu
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Kan
authors.forename: Tengling
authors.initials: T
authors.lastname: Ye
authors.forename: Li
authors.initials: L
authors.lastname: Zhao
authors.forename: Wen-Yong
authors.initials: WY
authors.lastname: Lai
authors.forename: Ruidong
authors.initials: R
authors.lastname: Xia
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Lanzani
authors.forename: Panagiotis E
authors.initials: PE
authors.lastname: Keivanidis
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
keywords: cathode interlayer; conjugated polyeletrolytes; inverted polymer solar cells; star-shaped molecule