Incorporation of ester groups into low band-gap diketopyrrolopyrrole containing polymers for solar cell applications
作者:Xiaolian Hu、Lijian Zuo、Weifei Fu、Thue T. Larsen-Olsen、Martin Helgesen、Eva Bundgaard、Ole Hagemann、Minmin Shi、Frederik C. Krebs、Hongzheng Chen
DOI:10.1039/c2jm31700a
日期:——
To increase the open circuit voltage (VOC) of polymer solar cells based on diketopyrrolopyrrole (DPP) containing polymers, the weakly electron-withdrawing thiophene-3,4-dicarboxylate unit was introduced into the polymer backbone. Two ester group functionalized DPP containing polymers, PCTDPP with a random structure and PDCTDPP with a regular structure, were designed and synthesized by the Stille coupling reaction. The resulting copolymers exhibit broad and strong absorption bands from 350 to 1000 nm with low optical band gaps below 1.40 eV. Through cyclic voltammetry measurements, it is found that regular PDCTDPP's HOMO energy level is 0.18 V lower than that of the corresponding random PCTDPP (−5.14 eV for PCTDPP and −5.32 eV for PDCTDPP). Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor were investigated. The PSC based on a PCTDPP:PCBM blend shows a power conversion efficiency (PCE) up to 3.52%, with a VOC of 0.66 V, a short circuit current (ISC) of 8.53 mA cm−2, and a fill factor (FF) of 0.63. For the PDCTDPP:PCBM blend, the highest VOC reaches a value of 0.84 V, and a final PCE (0.92%) is limited by the poor hole mobility of the active layer.
为了提高基于含二酮吡咯并吡咯(DPP)聚合物的聚合物太阳能电池的开路电压(VOC),在聚合物骨架中引入了弱电子吸收的噻吩-3,4-二甲酸单元。通过 Stille 偶联反应,设计并合成了两种酯基官能化的含 DPP 聚合物:无规结构的 PCTDPP 和规则结构的 PDCTDPP。所得到的共聚物在 350 至 1000 纳米范围内表现出宽而强的吸收带,光带隙低于 1.40 eV。通过循环伏安法测量发现,规则 PDCTDPP 的 HOMO 能级比相应的无规 PCTDPP 低 0.18 V(PCTDPP 为 -5.14 eV,PDCTDPP 为 -5.32 eV)。研究人员初步考察了与作为电子受体的 [6,6]- 苯基-C61-丁酸甲酯(PCBM)共混的共聚物的光伏特性。基于 PCTDPP:PCBM 混合物的 PSC 功率转换效率 (PCE) 高达 3.52%,VOC 为 0.66 V,短路电流 (ISC) 为 8.53 mA cm-2,填充因子 (FF) 为 0.63。对于 PDCTDPP:PCBM 混合物,最高 VOC 值达到 0.84 V,而最终 PCE(0.92%)则受限于活性层较差的空穴迁移率。