Control of Phase Separation of Benzothienoisoindigo-Benzodithiophene Copolymer for Organic Photovoltaics
Control of Phase Separation of Benzothienoisoindigo-Benzodithiophene Copolymer for Organic Photovoltaics
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DOI：
10.2494/photopolymer.29.565
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发表时间：
2016-01-01
影响因子：
0.8
通讯作者：
Saeki, Akinori
中科院分区：
文献类型：
--
作者：
Ide, Marina;Koizumi, Yoshiko;Saeki, Akinori
设计并合成了一种由苯并噻吩异靛蓝（BTIDG）和苯并二噻吩（BDT）组成的新型低带隙聚合物。凭借不对称的BTIDG部分，BDT - BTIDG共聚物在带隙（1.5 eV）和最高占据分子轨道（HOMO，-5.4 eV）方面均表现出适中的电化学性能。它们分别比先前的对称噻吩异靛蓝（TIDG）-BDT类似物宽0.4 eV和深0.5 eV。尽管BDT - BTIDG在氯苯等常见有机溶剂中具有高度溶解性，但苯基 - C - 61 - 丁酸甲酯（PCBM）的共混膜在200 nm以上的空间尺度上导致了较大的相分离，由于光干涉而产生结构色。我们使用氯仿和溶剂添加剂在一定程度上减轻了相分离，当BDT - BTIDG:PCBM = 1 : 2时，光电转换效率（PCE）为0.83%。这项工作表明共聚物的溶解性与最佳的本体异质结形态并无直接关联。
A new low-bandgap polymer composed of benzothienoisoindigo (BTIDG) and benzodithiophene (BDT) was designed and synthesized. By virtue of unsymmetrical BTIDG moiety, BDT-BTIDG copolymer exhibits moderate electrochemical properties in both bandgap (1.5 eV) and the highest occupied molecular orbital (HOMO, -5.4 eV). They are 0.4 eV wider and 0.5 eV deeper than those of previous symmetric thienoisoindigo (TIDG)-BDT analogue, respectively. Although the BDT-BTIDG is highly soluble in common organic solvents like chlorobenzene, the blend film of phenyl-C-61-butyric-acid-methyl ester (PCBM) caused a large phase separation over 200 nm spatial scale, leading to a structural color due to light interference. We have mitigated the phase separation to some extent using chloroform and solvent additive, giving the PCE of 0.83% for BDT-BTIDG:PCBM = 1 : 2. This work indicates that solubility of copolymer is not directly relevant to optimal bulk heterojunction morphology.