Collaborative Research: NSF-BSF: Understanding Semiconducting Polymers in High-Dielectric-Constant Environments

非技术总结：对“塑料”半导体的研究已经导致了可以收集太阳能并将其转化为电能的材料。然而，目前用这种半导体塑料制成的设备很复杂，需要两种材料才能有效地将光转化为电。目前的项目探讨最终是否可以简化这种结构，可能产生基于单一材料的设备。为此，将使用模型系统系统地研究局部环境对塑料半导体的电子和光学性质的影响，以测试预测通过使塑料半导体的局部环境更具极性可以生产更高效器件的理论。该项目所获得的基本见解将允许设计和生产新的塑料半导体，提高塑料太阳能电池的效率和潜在的稳定性，并可能简化其生产，使其最终能够以类似于报纸印刷的方式印刷。这些都是提高塑料半导体在一系列应用中的经济可行性的因素，反过来，将有助于减少温室气体排放，并促进零能耗住房和基于太阳能电池集成到温室中的低水强度农业等概念的实施。技术概要：计划中的工作旨在大大推进我们对高k环境如何影响聚合物半导体光电性能的基本理解。虽然功能聚合物的有效介电常数k可以通过化学设计或聚合物的周围环境来控制，但分子结构的变化也会影响其他特征，包括极性，分子堆积，相行为和电子特性。因此，很少有直接的结构/功能关系已被实验建立至今。在这个项目中，目前阻碍结构/功能相互关系的各种复杂性将通过以下方式来规避：i）尽可能多地将加工过程中的聚合物自组装与高k材料的引入分离，以允许进行清洁的前后比较，以及ii）追求新的自组装策略以创建分子杂化材料和共混物。这些方法允许调整自组装的长度尺度和特定的界面面积，并且反过来提供了将所追求的光电效应与可能影响光电特性/材料性能的其他因素分开的手段。在项目期间获得的知识将应用于聚合物太阳能电池，其通常依赖于供体：受体体异质结来实现有效的激子分裂。该项目的一个主要目标是确定是否有一种途径可以显着降低激子结合能（从而在有机太阳能电池中实现有效的激子分裂）通过修改相关半导体聚合物主链附近的k，或者如果确实需要修改主链本身。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

NON-TECHNICAL SUMMARY:Research into 'plastic' semiconductors has led to materials that can harvest the energy of the sun and convert it into electricity. Yet, current devices made with such semiconducting plastics are complex and require two materials to efficiently convert light into electricity. The current project explores whether eventually this structure could be simplified, possibly yielding devices based on a single material. For this, the effect of the local environment on the electronic and optical properties of the plastic semiconductor will be systematically investigated using model systems to test theories that predict that more efficient devices could be produced by making the local environment of the plastic semiconductor more polar. The fundamental insight achieved in this project will allow to design and produce new plastic semiconductors, improve the efficiency and potentially the stability of plastic-based solar cells, and will likely simplify their production so that they eventually could be printed similar to the way newspapers are printed. These all are factors that would improve the economic viability of plastic semiconductors in a range of applications and, in turn, would contribute to reduced greenhouse gas emission and facilitate implementation of concepts such as zero-energy housing and low-water-intensity farming based on solar cell integrations into greenhouses.TECHNICAL SUMMARY:The planned work aims to significantly advance our fundamental understanding of how high-k environments affect the optoelectronic properties of polymer semiconductors. While the effective dielectric constant, k, of functional polymers can be manipulated via chemical design or the surrounding of the polymer, changes in molecular structure to create a high-k polymers also affect other features, including polarity, molecular packing, phase behavior, and electronic properties. As a consequence, few direct structure/function relations have been experimentally established to date. In this project, various current complications that have hindered the delivery of structure/function interrelations will be circumvented via i) separating the polymer self-assembly during processing from the introduction of the high-k material as much as possible, to allow for a clean before/after comparisons, and ii) pursuing new self-assembly strategies to create molecular hybrid materials and blends. These approaches allow to tune the lengthscales and specific interfacial areas of the self-assembly and, in turn, provide means to disentangle sought-after optoelectronic effects from other factors that might impact optoelectronic properties/materials performance. The knowledge gained during the project will be applied to polymer solar cells, which generally rely on donor:acceptor bulk heterojunctions to achieve efficient exciton splitting. A main goal of the project is to delineate if there is ever a pathway to significantly lower the exciton binding energy (and thus realize efficient exciton splitting in organic solar cells) by modifying k in the vicinity of relevant semiconducting polymer backbones or if one really needs to modify the backbone itself.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.