Absence of Mixed Phase in Organic Photovoltaic Active Layers Facilitates Use of Green Solvent Processing
Absence of Mixed Phase in Organic Photovoltaic Active Layers Facilitates Use of Green Solvent Processing
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DOI：
10.1021/acs.jpcc.8b01600
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发表时间：
2018-05-24
影响因子：
3.7
通讯作者：
Toney, Michael F.
中科院分区：
文献类型：
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作者：
Oosterhout, Stefan D.;Savikhin, Victoria;Toney, Michael F.
我们检查的形态的供体分子：富勒烯有机光伏（OPV）的活性层，从“绿色溶剂”2-甲基-THF（m-THF），以及在铸膜溶液中的两个OPV的组成成分的构象处理。我们观察到，小分子（X2）在氯仿溶剂中有一个弱的自缔合，而它在m-THF中不自缔合。尽管存在这种差异，但最终加工的薄膜的形貌非常相似：层中存在可忽略的分子混合相，纯X2和纯富勒烯的畴尺寸为15-20 nm。我们将最终膜之间的这种相似性归因于干燥时X2的强聚集行为;因此溶剂或溶剂添加剂的变化对最终本体异质结形态仅具有微小影响。这与大多数其他OPV分子供体半导体系统形成对比，其他OPV分子供体半导体系统需要仔细调节溶剂和/或溶剂添加剂以实现最佳形态和光伏性能。我们认为，没有混合相是X2的强自聚集行为的结果，并且这种材料组合的关键特性使其对加工溶剂的变化具有鲁棒性。
We examine the morphology of a donor molecule:fullerene organic photovoltaic (OPV) active layer, processed from the "green solvent" 2-methyl-THF (m-THF), as well as the conformation of the two OPV constituent components in the casting solution. We observe that the small molecule (X2) has a weak association with itself in chloroform solvent, whereas it does not self-associate in m-THF. Despite this difference, the morphologies of the final processed films are extraordinarily similar: there is negligible molecularly mixed phase in the layer, and the domain sizes of the pure X2 and pure fullerene are 15-20 nm. We attribute this similarity between the final films to the strong aggregation behavior of X2 upon drying; changes in solvent or solvent additive have therefore only a minor effect on the final bulk heteroiunction morphology This contrasts with the majority of other OPV molecular donor semiconductor systems, which need careful tuning of solvent and/or solvent additive to achieve the optimal morphology and photovoltaic performance. We argue that the absence of a mixed phase is a result of the strong self-aggregation behavior of X2 and a key property of this material combination that makes it robust to a change in processing solvent.