Different Effect of the Additional Electron-Withdrawing Cyano Group in Different Conjugation Bridge: The Adjusted Molecular Energy Levels and Largely Improved Photovoltaic Performance

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• 作者：Huiyang Li ; Manman Fang ; Yingqin Hou ; Runli Tang ; Yizhou Yang ; Cheng Zhong ; Qianqian Li ; Zhen Li
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 18, 2016
• 年：2016
• 卷：8
• 期：19
• 页码：12134-12140
• 全文大小：386K
• 年卷期：0
• ISSN：1944-8252

文摘

Four organic sensitizers (LI-68–LI-71) bearing various conjugated bridges were designed and synthesized, in which the only difference between LI-68 and LI-69 (or LI-70 and LI-71) was the absence/presence of the CN group as the auxiliary electron acceptor. Interestingly, compared to the reference dye of LI-68, LI-69 bearing the additional CN group exhibited the bad performance with the decreased J_sc and V_oc values. However, once one thiophene moiety near the anchor group was replaced by pyrrole with the electron-rich property, the resultant LI-71 exhibited a photoelectric conversion efficiency increase by about 3 folds from 2.75% (LI-69) to 7.95% (LI-71), displaying the synergistic effect of the two moieties (CN and pyrrole). Computational analysis disclosed that pyrrole as the auxiliary electron donor (D′) in the conjugated bridge can compensate for the lower negative charge in the electron acceptor, which was caused by the CN group as the electron trap, leading to the more efficient electron injection and better photovoltaic performance.