4-Alkyl-3,5-difluorophenyl-Substituted Benzodithiophene-Based Wide Band Gap Polymers for High-Efficiency Polymer Solar Cells

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• 作者：Guangwu Li ; Xue Gong ; Jicheng Zhang ; Yahui Liu ; Shiyu Feng ; Cuihong Li ; Zhishan Bo
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：February 17, 2016
• 年：2016
• 卷：8
• 期：6
• 页码：3686-3692
• 全文大小：511K
• ISSN：1944-8252

文摘

Two novel polymers PTFBDT-BZS and PTFBDT-BZO with 4-alkyl-3,5-difluorophenyl substituted benzodithiophene as the donor unit, benzothiadiazole or benzooxadiazole as the acceptor unit, and thiophene as the spacer have been synthesized and used as donor materials for polymer solar cells (PSCs). These two polymers exhibited wide optical band gaps of about 1.8 eV. PSCs with the blend of PTFBDT-BZS:PC₇₁BM (1:2, by weight) as the active layer fabricated without using any processing additive and any postannealing treatment showed power conversion efficiency (PCE) of 8.24% with an open circuit voltage (V_oc) of 0.89 V, a short circuit current (J_sc) of 12.67 mA/cm², and a fill factor (FF) of 0.73 under AM 1.5G illumination, indicating that PTFBDT-BZS is a very promising donor polymer for PSCs. The blend of PTFBDT-BZO:PC₇₁BM showed a lower PCE of 5.67% with a V_oc of 0.96 V, a J_sc of 9.24 mA/cm², and an FF of 0.64. One reason for the lower PCE is probably due to that PTFBDT-BZO has a smaller LUMO offset with PC₇₁BM, which cannot provide enough driving force for charge separation. And another reason is probably due to that PTFBDT-BZO has a lower hole mobility in comparison with PTFBDT-BZS.