Solution-Processable Small Molecules for High-Performance Organic Solar Cells with Rigidly Fluorinated 2,2′-Bithiophene Central Cores

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• 作者：Zhenguo Wang ; Zuojia Li ; Jiang Liu ; Jun Mei ; Kai Li ; Ying Li ; Qiang Peng
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：8
• 期：18
• 页码：11639-11648
• 全文大小：599K
• 年卷期：0
• ISSN：1944-8252

文摘

Small molecules containing an oligothiophene backbone are simple but effective donor materials for organic solar cells (OSCs). In this work, we incorporated rigid 2,2′-bithiophene (BT) or fluorinated 2,2′-bithiophene (FBT) as the central unit and synthesized two novel small molecules (TTH-D3TRh and TTF-D3TRh) with an oligothiophene backbone and 3-ethylrhodanine end groups. Both molecules exhibit good thermal stability as well as strong and broad absorption. The fluorination of the BT central unit made TTF-D3TRh possess a relatively lower-lying HOMO energy level, better molecular stacking, and higher mobility in comparison with those of TTH-D3TRh. Conventional OSCs were fabricated to evaluate the photovoltaic property of these two molecules. Without extra post-treatments, the conventional devices based on TTH-D3TRh and TTF-D3TRh showed high PCEs of 5.00 and 5.80%, respectively. The TTF-D3TRh device exhibited a higher performance, which can be attributed to the improved V_oc of 0.92 V, J_sc of 10.04 mA cm^–2, and FF of 62.8%. Using an inverted device structure, the OSCs based on TTH-D3TRh and TTF-D3TRh showed largely elevated PCEs of 5.89 and 7.14%, respectively. The results indicated that the structurally simple TTH-D3TRh and TTF-D3TR molecules are potential donor candidates for achieving highly efficient OSCs. The strategy of fluorination and rigidity designation is an effective approach to develop oligothiophene-based small molecular donors for highly efficient solar cell applications.