SGER: Initiated Chemical Vapor Deposition Synthesis and Design of Polymers for Alternative Energies

CBET-0820608 LAU这个小型探索性研究(SGER)项目旨在开发一种基于启动化学气相沉积(ICVD)的新设计和合成方法，以制造用于太阳能电池的半导体、共轭聚合物，以提高效率和性能。智力优势：在基于聚合物的体相异质结太阳能电池中，效率低下的原因是聚合物的高带隙导致与太阳光谱的不匹配，以及由于结构和形态缺陷导致聚合物中电荷的产生和传输普遍较差。在使用无机纳米晶二氧化钛的混合体系中，无论是否有染料敏化，太阳能电池的效率都受到聚合物填充介孔二氧化钛的不良影响。其中一些问题源于使用基于液体的加工方法在太阳能电池组中形成共轭聚合物薄膜。由于未经改性的共轭聚合物通常是难溶和不溶的，在这些聚合物上添加增溶侧链会导致溶解性，从而导致加工性。然而，侧基的加入可能会导致结晶度、形态和稳定性的不良变化，并导致聚合物的降解。此外，聚合物的性能往往对溶剂的选择和去除溶剂的条件很敏感。ICVD依赖于使用单体和蒸汽形式的热激活引发剂/催化剂在表面上直接聚合固体聚合物薄膜。通过绕过液相，不需要溶剂，因此ICVD获得了极大的加工自由度，不仅使未经改性的共轭聚合物易于加工，而且为设计由于溶剂限制或不相容而在液相中无法获得的新型材料开辟了可能性。此外，在没有宏观相分离和从不利的溶剂相互作用中分离的问题下，ICVD作为一种无溶剂处理技术有望实现共轭聚合物与其对接之间不同相的亲密的纳米级混合。具体的研究目标是：(1)展示利用ICVD合成具有作为太阳能电池材料的可行性能的单体和共聚单体的共轭聚合物；以及(2)通过集成ICVD和热蒸发和旋涂等加工技术来展示施主和受主相之间的紧密接触，以产生异质结，类似于通过利用CVD和其他加工技术在微电子制造中成功应用的范例。广泛的影响：该计划的动机是需要找到替代能源解决方案，以减少我们对化石燃料的依赖，保护我们的环境免受其破坏性影响，并使地球更可持续。由于太阳能在很大程度上仍是一种未开发的资源，该计划是旨在推动这种替代能源技术发展的第一步。除此之外，通过这项工作设计良好的共轭聚合物可以在柔性电子产品、有机发光二极管(OLED)设备和生物医学中得到应用。该计划将整合强大的教育成分，通过指导德雷克斯？S的高中生和本科生开展许多外展计划；通过与地区高中发展关系，提供实践机会，测试太阳能电池的长期稳定性，以此来向学生传授负责任的技术。该计划旨在从少数群体和代表性不足的群体中积极招聘。由于ICVD方法的适用性和多功能性，研究结果将被传播，并有望催生多学科研究。

CBET-0820608LauThis Small Grant for Exploratory Research (SGER) project is aimed at developing a new design and synthesis methodology based on initiated chemical vapor deposition (iCVD) to make semiconducting, conjugated polymers for use in solar cells with enhanced efficiency and performance.Intellectual merit: In bulk heterojunction polymer-based solar cells, inefficiencies are attributed to the high band gap of polymers leading to a mismatch with the solar spectrum, and generally poor charge generation and transport in the polymer due to structural and morphological defects. In hybrid systems using inorganic, nanocrystalline titania, with or without dye sensitization, solar cell efficiency has been hampered by the poor filling of the mesoporous titania with the polymer. Some of these issues stem from using liquid-based processing methods to form the conjugated polymer thin films in the solar cell stack. Since unmodified conjugated polymers are typically intractable and insoluble, addition of solubilizing side chains on these polymers induce solubility and therefore processability. However, addition of side groups may result in undesirable changes in crystallinity, morphology and stability and lead to degradation of the polymer. Further, polymer properties are often sensitive to the choice of solvent and the conditions for solvent removal. iCVD relies on the direct polymerization of a solid polymer thin film on a surface using monomers and thermally activated initiators/catalysts in the vapor form. By circumventing the liquid-phase, there is no requirement for solvents, and therefore iCVD gains significant processing freedom, not only in making unmodified conjugated polymers tractable, but also opening up the possibility of designing novel materials which would otherwise have been unattainable in the liquid phase due to solvent constraints or incompatibilities. Further, without the issues of macroscale phase separation and demixing from adverse solvent interactions, iCVD as a solventless processing technique is expected to enable intimate, nanoscale mixing of dissimilar phases between the conjugated polymer and its counter-junction.The specific research objectives are (1) to demonstrate the synthesis of conjugated polymers using iCVD for a selected list of monomers and co-monomers, which will have viable properties as solar cell materials; and (2) to demonstrate the tight contact between the donor and acceptor phases by integrating iCVD and processing techniques like thermal evaporation and spin coating to produce the heterojunctions, similar to the paradigm that has been successfully applied in microelectronics fabrication through the utilization of CVD and other processing techniques.Broader impact: This program is motivated by the need to discover alternative energy solutions to reduce our dependency on fossil fuel, protect our environment from its damaging effects, and enable a more sustainable Earth. With solar energy remaining a largely untapped resource, this program is a first step that aims to fuel the technological development of this alternative energy. Beyond this, well-designed conjugated polymers from this work could find applications in flexible electronics, organic light-emitting diode (OLED) devices, and biomedicine. This program will integrate a strong educational component through mentoring high school and undergraduate students from Drexel?s many outreach programs; by growing relationships with area high schools to provide hands-on opportunities to test the long term stability of solar cells as a way to inform students of responsible technology. This program aims to actively recruit from minority and underrepresented groups. Research results will be disseminated and are expected to germinate multidisciplinary research because of the applicability and versatility of the iCVD approach.