Higher Efficiency Organic Solar Cells via Continuous Processing under Optimum Shearing Conditions

太阳每小时提供的能量足以满足人类全年的能源需求。充分开发这一丰富的可持续资源将需要有效的手段，其经济收获。有机太阳能电池由具有各种碳基添加剂的聚合物组成，基于其灵活性，轻质性和大面积覆盖的潜力，是将太阳能转化为电能的有前途的车辆。然而，目前的有机太阳能电池的转换效率相对较低，并且它们的成本高得令人望而却步。使用高通量连续制造方法，如喷墨印刷和卷对卷加工，有可能降低制造成本。此外，如果有机电池微结构在其连续制造期间被有利地控制，则其转换效率可以增加。 该项目旨在对聚合物/添加剂混合物的连续混合和沉积过程中的剪切过程的动力学有一个基本的了解，以便在降低制造成本的同时获得具有更高光转换效率的太阳能电池结构。这一多学科项目将成为研究生的一个肥沃的培训基地，并将纳入为科学和工程领域代表性不足的群体开展的外联活动。有机太阳能电池的光活性层由聚合物-小分子纳米复合材料组成，并且小分子组分的晶体尺寸和结晶度是光转换效率和长期稳定性的关键微观结构因素。本研究将研究在薄膜沉积之前和期间应用于聚合物-小分子纳米悬浮液的变形历史如何影响小分子的晶体尺寸和成核密度，从而影响有机太阳能电池的效率和稳定性。（1）绘制纳米复合材料组成、溶液剪切条件和所得小分子结晶结果之间的加工-结构关系;（2）执行与工业相关速率相容的预剪切和涂覆工艺，以在膜沉积之前和期间施加目标剪切历史;以及（3）评估太阳能电池性能以确定小分子结晶对光转换效率和稳定性的影响。通过系统地探索聚合物流变学和加工条件对小分子剪切诱导结晶的影响，将建立基于数学建模的设计规则，以指导能够引起所需结晶结果的连续加工方法的开发。

Every hour the sun provides more than enough energy to satisfy the annual energy requirements of the human population. Full exploitation of this abundant sustainable resource will require efficient means for its economical harvesting. Organic solar cells, which are composed of polymers with various carbon-based additives, are promising vehicles to convert solar energy into electricity on the basis of their flexibility, lightweight nature, and potential for large-area coverage. The conversion efficiencies of current organic solar cells, however, are relatively low and their costs are prohibitively high. The use of high-throughput continuous manufacturing methods, such as inkjet printing and roll-to-roll processing has the potential to reduce the cost of manufacturing. Furthermore, if the organic cell microstructures are favorably controlled during their continuous fabrication, their conversion efficiencies can be increased. This project aims to develop a fundamental understanding of the dynamics of the shearing processes during continuous mixing and deposition of the polymer/additive mixtures so that solar cell structures with greater light conversion efficiencies can be obtained while reducing the manufacturing expense. This multidisciplinary project will serve as a fertile training ground for graduate students and will be integrated into outreach activities for underrepresented groups in science and engineering. Photoactive layers of organic solar cells are comprised of polymer-small molecule nanocomposites, and the crystal size and crystallinity of the small molecule component are critical microstructural factors for light conversion efficiency and long-term stability. This research will investigate how the deformation history applied to polymer-small molecule nanosuspensions prior to and during film deposition affects crystal sizes and nucleation densities of small molecules to impact the efficiency and stability of organic solar cells. This objective will be accomplished by: (1) mapping processing-structure relationships between nanocomposite composition, solution shearing conditions, and resultant small molecule crystallization outcomes; (2) executing a preshearing and coating process that is compatible with industrially-relevant rates to impose target shear histories prior to and during film deposition; and (3) evaluating solar cell performance to determine the effects of small molecule crystallization on light conversion efficiency and stability. By systematically exploring the effects of polymer rheology and processing conditions on the shear induced crystallization of small molecules, mathematical modeling-based design rules will be established to guide the development of continuous processing methods capable of evoking desired crystallization outcomes.