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arXiv 1106.3536cond-mat.mtrl-sci
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一种新的基于图形的表征形貌的公式及其在有机太阳能电池中的应用

A novel graph-based formulation for characterizing morphology with application to organic solar cells

Olga Wodo, Srikanta Tirthapura, Sumit Chaudhary, Baskar Ganapathysubramanian

摘要:

有机太阳能电池由于其低成本、卷对卷可制造性和机械灵活性的承诺而具有广泛使用的潜力。然而,部署受到其相对较低的功率转换效率的阻碍。在过去的十年中,通过各种策略在增强这些设备的功率转换方面取得了重大进展。一种这样的方法是基于形态控制。这是因为形态影响太阳能转换中涉及的所有现象:光吸收和电子-空穴对(激子)产生;激子扩散和解离成自由电荷;以及电荷向电极的传输。在实验表征和计算建模的进展,现在允许重建和成像的薄膜形态。这开辟了将制造与形态以及形态与性能合理联系起来的可能性。因此,一套全面的计算工具来快速量化和分类薄膜的异质内部结构,将是非常宝贵的连接过程,结构和性能。我们提出了一种新的基于图形的框架,有效地构建了一个广泛的物理意义的形态描述符。根据有机太阳能电池内的物理子过程,这些形态描述符被进一步分类。该方法的动机之间的等价性的离散形态和标记,加权,无向图。我们利用这种方法来提出与结构表征相关的关键问题。随后,我们构建各种效率的估计和上界。通过表征热退火对薄膜形态随时间演变的影响来展示该方法。最后,我们制定自然的扩展,以表征结晶度和各向异性的形态使用的框架。

英文摘要:

Organic solar cells have the potential for widespread usage due to their promise of low cost, roll-to-roll manufacturability, and mechanical flexibility. However, deployment is impeded by their relatively low power conversion efficiencies. The last decade has seen significant progress in enhancing the power conversion of these devices through various strategies. One such approach is based on morphology control. This is because morphology affects all phenomena involved in solar conversion: light absorption and electron-hole pair (exciton) generation; exciton diffusion and dissociation into free charges; and transport of charges to the electrodes. Progress in experimental characterization and computational modeling now allow reconstruction and imaging of the thin film morphology. This opens up the possibility of rationally linking fabrication with morphology, as well as morphology with performance. In this context, a comprehensive set of computational tools to rapidly quantify and classify the heterogeneous internal structure of thin films will be invaluable in linking process, structure and property. We present a novel graph-based framework to efficiently construct a broad suite of physically meaningful morphology descriptors. These morphology descriptors are further classified according to the physical subprocesses within an organic solar cells. The approach is motivated by the equivalence between a discretized morphology and a labeled, weighted, undirected graph. We utilize this approach to pose key questions related to structure characterization. We subsequently construct estimates and upper bounds of various efficiencies. The approach is showcased by characterizing the effect of thermal annealing on time-evolution of a thin film morphology. We conclude by formulating natural extensions to characterize crystallinity and anisotropy of the morphology using the framework.

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