title: Multi-Chlorine-Substituted Self-Assembled Molecules As Anode Interlayers: Tuning Surface Properties and Humidity Stability for Organic Photovoltaics.
abstract: Self-assembled small molecules (SASMs) are effective materials to improve the interfacial properties between a metal/metal oxide and the overlying organic layer. In this work, surface modification of indium tin oxide (ITO) electrode by a series of Cl-containing SASMs has been exploited to control the surface properties of ITO and device performance for organic photovoltaics. Depending on the position and degrees of chlorination for SASMs, we could precisely manipulate the work function of the ITO electrode, and chemisorption of SASMs on ITO as well. Consequently, a power conversion efficiency (PCE) of 9.1% was achieved with tetrachlorobenzoic acid (2,3,4,5-CBA) SASM by a simple solution-processed method based on PTB7-Th-PC71BM heterojunction. More intriguingly, we discover that device performance is closely associated with the humidity of ambient conditions. When the humidity increases from 35-55% to 80-95%, device performance with 2,3,4,5-CBA has negligible reduction, in contrast with other SASMs that show a sharp reduction in PCEs. The increased device performance is primarily attributed to a matched work function, stable chemisorption, and beneficial wettability with overlying active layer. These findings suggest an available approach for manufacturing inexpensive, stable, efficient, and environmentally friendly organic photovoltaics by appropriate self-assembled small molecules.
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Cheng
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Liqiang
authors.initials: L
authors.lastname: Huang
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Lifu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Ai
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Lie
authors.initials: L
authors.lastname: Chen
authors.affiliation: College of Chemistry and ‡Jiangxi Provincial Key Laboratory of New Energy Chemistry/Institute of Polymers, Nanchang University , 999 Xuefu Avenue, Nanchang 330031, China.
authors.forename: Yiwang
authors.identifier: http://orcid.org/0000-0003-4709-7623
authors.initials: Y
authors.lastname: Chen
keywords: chemisorption stability; device stability; humidity stability; multi-chlorine-substituted; self-assembled small molecule