Polymorphisms and morphological studies of a difluorobenzothiadiazole conjugated copolymer with 7.8% polymer solar cell efficiency
Polymorphisms and morphological studies of a difluorobenzothiadiazole conjugated copolymer with 7.8% polymer solar cell efficiency
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DOI：
10.1039/c4ta06228k
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发表时间：
2015-02
影响因子：
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通讯作者：
Chi-feng Huang;Jen-Yun Chang;Sinian Huang;Kuan-Yi Wu;J. Jheng;Wei‐Tsung Chuang;Chain‐Shu Hsu;Chien-Lung Wang
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文献类型：
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作者：
Chi-feng Huang;Jen-Yun Chang;Sinian Huang;Kuan-Yi Wu;J. Jheng;Wei‐Tsung Chuang;Chain‐Shu Hsu;Chien-Lung Wang
本文研究了5,6-二氟苯-2,1,3-噻二唑(FBT) -季噻吩（Th4）交替共聚物（PTh4FBT）的结构表征，以及PTh4FBT的结晶性质对PTh4FBT - pc71bm形貌和器件性能的影响。5,6-二氟-4,7-二（噻吩-2-基）苯并噻唑（Th2FBT）的单晶结构首次证实了含FBT分子的低构象偏好。由于结晶过程不能帮助统一Th2FBT的构象，因此必须仔细研究PTh4FBT晶态中的链内构象和链间c移。通过对比PTh4FBT的二维WAXS图和Cerius2分子模型模拟的衍射图，发现含有反构象和有限链间c移的PTh4FBT晶格生成的衍射图与实验结果最吻合。TEM和GI WAXS形貌研究表明，PTh4FBT的面对面链间堆叠使聚合物具有很强的结晶性，并在PTh4FBT - pc71bm共混体系中产生了较大的偏析。通过使用1-氯萘添加剂降低了团聚尺寸。优化后的形貌提高了Jsc和FF。单结PTh4FBT-PC71BM基聚合物太阳能电池的PCE为7.75%，Voc为0.76 V， Jsc为14.36 mA cm−2，FF为71.0%。
This study presents the structural characterization of a 5,6-difluorobenzo-2,1,3-thiadiazole (FBT)–quaterthiophene (Th4) alternating copolymer (PTh4FBT) and how the crystalline nature of PTh4FBT affects the PTh4FBT–PC71BM morphology and the device performances. The single crystal structure of 5,6-difluoro-4,7-di(thiophen-2-yl)benzothiadiazole (Th2FBT) first confirms the low conformational preference of the FBT containing molecule. Since the crystallization process does not assist in unifying the conformation of Th2FBT, both intrachain conformation and interchain c-shifts in the crystalline state of PTh4FBT have to be scrutinized. By comparing the 2D WAXS pattern of PTh4FBT and the simulated patterns generated from Cerius2 molecular modeling, it was found that the diffraction pattern generated from the lattice containing PTh4FBT with anti-conformation and limited interchain c-shift matches best with the experimental one. The face-to-face interchain stacking of PTh4FBT rendered strong crystalline nature to the polymer and caused large segregation in the PTh4FBT–PC71BM blend system, which was indicated by the TEM and GI WAXS morphological studies. The aggregation size was reduced via the use of the 1-chloronaphthalene additive. The optimized morphology led to improved Jsc and FF. The single-junction PTh4FBT–PC71BM based polymer solar cells deliver a high PCE of 7.75% with a Voc of 0.76 V, a Jsc of 14.36 mA cm−2, and a FF of 71.0%.