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Correlating the electron-donating core structure with morphology and performance of carbon oxygen-bridged ladder-type non-fullerene acceptor based organic solar cells

DOI: 10.1016/j.nanoen.2019.04.053 DOI Help

Authors: Wei Li (Wuhan University of Technology) , Zuo Xiao (National Center for Nanoscience and Technology, Beijing) , Jinlong Cai (Wuhan University of Technology) , Joel A. Smith (University of Sheffield) , Emma L. K. Spooner (University of Sheffield) , Rachel C. Kilbride (University of Sheffield) , Onkar S. Game (University of Sheffield) , Xianyi Meng (National Center for Nanoscience and Technology, Beijing) , Donghui Li (Wuhan University of Technology) , Huijun Zhang (Wuhan University of Technology) , Mengxue Chen (Wuhan University of Technology) , Robert S. Gurney (Wuhan University of Technology) , Dan Liu (Wuhan University of Technology) , Richard A. L. Jones (University of Sheffield) , David Lidzey (University of Sheffield) , Liming Ding (National Center for Nanoscience and Technology, Beijing) , Tao Wang (University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nano Energy , VOL 61 , PAGES 318 - 326

State: Published (Approved)
Published: July 2019
Diamond Proposal Number(s): 120419

Abstract: The chemical structure of non-fullerene acceptors (NFAs) affects their light-harvesting capabilities, energy levels and molecular orders, all of which play a crucial role in determining the efficiency of organic solar cells (OSCs). In this work, we have systematically investigated a series of ladder-type NFAs having different carbon-oxygen-bridged electron-donating cores, and revealed the effects of core structures and film casting conditions on molecular ordering and performance of OSCs. We found that NFAs containing the thieno [3,2-b]thiophene centered, 6 or 8 fused rings (i.e. COi6DFIC, COi8DFIC) exhibit narrower optical band gaps than NFAs containing the benzene centered, 5 or 7 fused rings (i.e. COi5DFIC, COi7DFIC). NFAs containing less fused rings in the carbon-oxygen-bridged core (i.e. COi5DFIC and COi6DFIC) exhibit edge-on molecular orientation in the blends with face-on oriented PTB7-Th donor, and result in low device efficiency. Although NFAs containing more fused rings (i.e. COi7DFIC and COi8DFIC) possess a pronounced flat-on lamellar crystalline structure in the pure state, the crystallization can be reduced when blending with PTB7-Th and under hot-substrate casting, while the lamella in COi8DFIC can be effectively suppressed to form face-on H- and J-type aggregates, leading to enhanced efficiency.

Keywords: Organic solar cells; Non-fullerene acceptors; Molecular order; Device efficiency

Subject Areas: Chemistry, Energy

Beamlines: I07-Surface & interface diffraction