Synthesis of low bandgap polymers based on thienoquinodimethane units and their applications in bulk heterojunction solar cells
作者:Tomokazu Umeyama、Yusuke Watanabe、Masaaki Oodoi、Douvogianni Evgenia、Tetsuya Shishido、Hiroshi Imahori
DOI:10.1039/c2jm33637e
日期:——
A non-fused ring building block of an electron-rich quinoid structure, 2,5-thienoquinodimethane, has been synthesized and used in the synthesis of novel donor (D)–acceptor (A) type low bandgap polymers for the first time. Namely, 2,5-thienoquinodimethane with 4-(tert-butyl)phenyl or 4-(octyloxy)phenyl side chain as a solubilizing group was copolymerized with an electron-deficient diketopyrrolopyrrole subunit (PQD1 and PQD2, respectively). These polymer films exhibited broad and intense absorption bands in the region of 400–1000 nm. Photovoltaic devices with active layers consisting of PQD1 or PQD2 with [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) revealed a broad photoresponse range covering from 400 to 1000 nm, whereas the power conversion efficiencies (η) were found to be moderate (1.44% for PQD1 and 0.96% for PQD2) under the illumination of AM 1.5G, 100 mW cm−2. The superior η value of the PQD1:[70]PCBM-based device relative to the PQD2:[70]PCBM-based device can be attributed to the more favorable phase separation nanostructure in the active layer as well as the higher crystallinity of PQD1 than PQD2. These results provide valuable, basic guidelines for rational designs of quinoidal heterole-based low bandgap polymers for high performance organic solar cells.
一种非熔融环状结构单元——富电子喹啉结构2,5-噻吩喹啉二甲烷首次被合成并用于新型供体(D)-受体(A)型低带隙聚合物的合成。即,将具有4-(叔丁基)苯基或4-(辛氧基)苯基侧链作为增溶剂的2,5-噻吩喹啉二甲烷与电子缺陷二酮吡咯吡咯亚基(分别为PQD1和PQD2)共聚。这些聚合物薄膜在400-1000 nm区域表现出宽而强烈的吸收带。由PQD1或PQD2与[6,6]-苯基-C71-丁酸甲酯([70]PCBM)组成的活性层的光伏器件显示出从400到1000 nm的宽光响应范围,而在AM 1.5G、100 mW cm-2的照明下,功率转换效率(η)适中(PQD1为1.44%,PQD2为0.96%)。与基于PQD2:[70]PCBM的器件相比,基于PQD1:[70]PCBM的器件具有更优越的η值,这可以归因于活性层中更有利的相