Nanoscale Morphology of Doctor Bladed versus Spin-Coated Organic Photovoltaic Films
Nanoscale Morphology of Doctor Bladed versus Spin-Coated Organic Photovoltaic Films
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DOI：
10.1002/aenm.201701269
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发表时间：
2017-11-22
影响因子：
27.8
通讯作者：
Ganapathysubramanian, Baskar
中科院分区：
文献类型：
--
作者：
Pokuri, Balaji Sesha Sarath;Sit, Joseph;Ganapathysubramanian, Baskar
有机光致发光效率的最新进展是通过明智地选择导致“期望”形态的加工条件来驱动的。形态学研究的一个重要主题是量化加工条件对形态学的影响，并将其与器件效率相关联。最先进的形态量化方法提供了电影平均或2D投影的功能，只有间接相关的性能，使因果推理不平凡。然而，材料的3D分布提供了一种直接将处理映射到性能的方法。在本文中，两个最近开发的技术集成重建的3D形态和随后的转换成直观的形态矢量，全面的图像和量化形态。这些技术应用于通过刮涂和旋涂产生的薄膜，另外还研究了热退火的影响。结果发现，所有样品的形态表现出非常高的连接到电极。毫不奇怪，热退火一致地增加样品中的平均畴尺寸，有助于激子的产生。此外，退火还改善了界面的平衡，增强了激子解离。形态描述符影响每个阶段的电子物理学（激子产生，解离，和电荷传输）的比较表明，自旋退火的样品表现出优越的上级基于形态的性能指标。这表明基于叶片的方法（工艺优化）的改进空间很大，用于形态调整，以提高大面积器件的性能。
Recent advances in efficiency of organic photovoltaics are driven by judicious selection of processing conditions that result in a "desired" morphology. An important theme of morphology research is quantifying the effect of processing conditions on morphology and relating it to device efficiency. State-of-the-art morphology quantification methods provide film-averaged or 2D-projected features that only indirectly correlate with performance, making causal reasoning nontrivial. Accessing the 3D distribution of material, however, provides a means of directly mapping processing to performance. In this paper, two recently developed techniques are integrated-reconstruction of 3D morphology and subsequent conversion into intuitive morphology descriptors-to comprehensively image and quantify morphology. These techniques are applied on films generated by doctor blading and spin coating, additionally investigating the effect of thermal annealing. It is found that morphology of all samples exhibits very high connectivity to electrodes. Not surprisingly, thermal annealing consistently increases the average domain size in the samples, aiding exciton generation. Furthermore, annealing also improves the balance of interfaces, enhancing exciton dissociation. A comparison of morphology descriptors impacting each stage of photophysics (exciton generation, dissociation, and charge transport) reveals that spin-annealed sample exhibits superior morphology-based performance indicators. This suggests substantial room for improvement of blade-based methods (process optimization) for morphology tuning to enhance performance of large area devices.