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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

2019; Elsevier BV; Volume: 61; Linguagem: Inglês

10.1016/j.nanoen.2019.04.053

2211-3282

Wei Li, Zuo Xiao, Jinlong Cai, Joel A. Smith, Emma L. K. Spooner, Rachel C. Kilbride, Onkar S. Game, Xianyi Meng, Donghui Li, Huijun Zhang, Mengxue Chen, Robert S. Gurney, Dan Liu, Richard Jones, David G. Lidzey, Liming Ding, Tao Wang,

Molecular Junctions and Nanostructures

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.