EAPSI: Investigating Intermolecular Interactions in the Formation of Polymer-Based Nanowires

由于易于加工，半导体聚合物有望提供低成本的电子设备，如太阳能电池和晶体管。已经确定了允许聚（3-己基噻吩）（P3HT）（一种广泛研究的半导体聚合物）结晶成纳米线（NWs）的制造条件，这可以改善太阳能电池？年代效率。本项目旨在了解P3HT组装成NWs的过程。NW取向和聚合物链相对于衬底的取向都是控制太阳能电池中有效传输电荷的关键参数。为了表征NWs的结构特征，将使用近边缘x射线吸收精细结构（NEXAFS），这是一种高度专业化的技术，能够证明薄膜的分子取向直至材料的单层。浦项科技大学表面和电子器件表征专家Kilwon Cho博士将主持这项研究，为美国研究生提供NEXAFS分析的重要途径和专业知识。该项目将重点研究沉积在支撑基板上的石墨烯P3HT的表面结晶。利用P3HT的亚稳溶液，具有强大的结晶驱动力，但不足以诱导均匀结晶，可以在石墨烯上选择性地形成P3HT的NWs。在结晶过程中，溶液中的聚合物链与石墨烯和底层衬底相互作用。利用NEXAFS等表面表征技术，系统研究石墨烯沉积在改性衬底上的NW生长，将揭示P3HT的表面特性和形态演变。这将有助于我们确定分子间作用力对P3HT结晶的影响。最终，NWs的有益影响将通过太阳能电池的制造和表征来评估。美国国家科学基金会EAPSI奖与韩国国家研究基金会合作资助。该奖项由美国国家科学基金会和韩国研究财团共同资助。

Semiconducting polymers promise to deliver low cost electronic devices such as solar cells and transistors due to their easy processabililty. Fabrication conditions have been identified that allows poly(3-hexyl thiophenes) (P3HT), an extensively studied semiconducting polymer, to crystallize into nanowires (NWs), which can improve a solar cell?s efficiency. This project aims to understand the assembly of P3HT into NWs. Both the NW alignment and the orientation of the polymer chains with respect to the substrate are crucial parameters to control for ensuring efficient transport of charges in solar cells. In order to characterize the structural features of the NWs, near edge X-ray absorption fine structure (NEXAFS), a highly specialized technique capable of proving the molecular orientation of thin films down to monolayers of the material will be used. Dr. Kilwon Cho, an expert in surface and electronic device characterization at Pohang University of Science and Technology, will be the host for this research, providing a U.S. graduate student vital access and expertize for NEXAFS analysis.This project will focus on the surface crystallization of P3HT from graphene deposited on supporting substrates. Utilizing a metastable solution of P3HT, with a strong driving force for crystallization that is not sufficient to induce homogenous crystallization, NWs of P3HT will be formed selectively on graphene. During the crystallization, the polymer chains in solution interact with graphene and the underlying substrate. A systematic study of the NW growth from graphene deposited on modified substrates employing surface characterization techniques such as NEXAFS will unveil the surface properties and the morphology evolution of P3HT. This will help us determine the effects of intermolecular forces on the P3HT crystallization. Ultimately, the beneficial effects of the NWs will be assessed by the fabrication and characterization of solar cells. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Korea.This award is jointly funded by NSF and the National Research Foundation of Korea.