Correlating Structure with Function in Thermally Annealed PCDTBT:PC70BM Photovoltaic Blends
Correlating Structure with Function in Thermally Annealed PCDTBT:PC70BM Photovoltaic Blends
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DOI：
10.1002/adfm.201102510
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发表时间：
2012-04
影响因子：
19
通讯作者：
Tao Wang;Andrew J Pearson;A. Dunbar;P. Staniec;Darren C. Watters;Hunan Yi;A. Ryan;Richard A. L. Jones-Richa
中科院分区：
文献类型：
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作者：
Tao Wang;Andrew J Pearson;A. Dunbar;P. Staniec;Darren C. Watters;Hunan Yi;A. Ryan;Richard A. L. Jones-Richa
使用一系列光学探针来研究咔唑共聚物聚[N-9 '-十七烷基-2，7-咔唑-alt-5，5-（4'，7 '-二-2-噻吩基-2'，1 '，3'-苯并噻二唑）（PCDTBT）和电子接受富勒烯衍生物（6，6）-苯基C70-丁酸甲酯（PC 70 BM）的光伏适用混合物的纳米级结构和电子功能。特别地，表明PCDTBT：PC 70 BM共混物薄膜的玻璃化转变温度对相对共混比或膜厚度（在1：4共混比下）不敏感，但对浇铸溶剂和其上沉积的基底类型敏感。结果发现，共混物的玻璃化转变温度降低退火;观察结果与PCDTBT分子之间的π-π堆叠的破坏一致。减少的π-π堆叠与热退火膜中减少的空穴迁移率相关。有人认为，这解释了这种退火方案未能大幅提高器件效率的原因。退火研究表明，当在155 °C或高于155 °C下退火时，共混物仅经历粗相分离，表明PCDTBT：PC 70 BM共混物具有有希望的形态稳定性程度。
A range of optical probes are used to study the nanoscale‐structure and electronic‐functionality of a photovoltaic‐applicable blend of the carbazole co‐polymer poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PCDTBT) and the electronic accepting fullerene derivative (6,6)‐phenyl C70‐butyric acid methyl ester (PC70BM). In particular, it is shown that the glass transition temperature of a PCDTBT:PC70BM blend thin‐film is not sensitive to the relative blend‐ratio or film thickness (at 1:4 blending ratio), but is sensitive to casting solvent and the type of substrate on which it is deposited. It is found that the glass transition temperature of the blend reduces on annealing; an observation consistent with disruption of π–π stacking between PCDTBT molecules. Reduced π–π stacking is correlated with reduced hole‐mobility in thermally annealed films. It is suggested that this explains the failure of such annealing protocols to substantially improve device‐efficiency. The annealing studies demonstrate that the blend only undergoes coarse phase‐separation when annealed at or above 155 °C, suggesting a promising degree of morphological stability of PCDTBT:PC70BM blends.