Improving DFT Modeling of EPR Data for Small Molecule Organic Photovoltaics

项目总结 电子从一个氧化还原活性部位到另一个氧化还原活性部位的运动是 许多生物系统，包括呼吸和光合作用。在自然光合作用中， 光系统II(PSII)催化分解水的反应，被视为 设计新的太阳能设备。这个设计过程的一个关键部分是充分理解电子 较小模型系统中的传输过程。我们最近研究了电子转移 结合电子的聚合物-富勒烯太阳能器件(体异质结太阳能电池) 顺磁共振(EPR)实验采用密度泛函理论(DFT)计算。 然而，我们发现，将小分子齐聚物与全聚合物的实验结果进行比较 这一系统使得对结果的解释变得困难。我们假设，与我们的DFT相比 直接对小分子齐聚物的结果进行计算将允许更好地评估 计算值与实验值吻合较好。重要的是要确定什么是函数 如果要使用DFT计算来指导太阳能电池设计，则适用。在目标1中，我们将 确定哪些官能团适当地模拟了含有硅和锗的低聚物 中心原子(而不是更常见的碳)。在目标2中，我们将确定真实的 通过比较跨越范围的低聚物的结果来确定电荷离域的程度 建议使用非本地化长度。在这项工作结束时，我们将扩展 了解如何对电子捐赠系统进行建模，并提供了可用于 新开发的太阳能装置的模型，将使这种装置在经济上更可行 并减少我们对化石燃料的依赖。

PROJECT SUMMARY The movement of an electron from one redox active site to another is central to the function of many biological systems including respiration and photosynthesis. In natural photosynthesis, Photosystem II (PSII) catalyzes the water splitting reaction and is seen as a template for designing new solar devices. A critical part of this design process is to fully understand electron transfer processes in smaller model systems. We have recently investigated electron transfer in polymer-fullerene solar devices (bulk heterojunction solar cells) by combining electron paramagnetic resonance (EPR) experiments with density functional theory (DFT) calculations. However, we found that comparing small oligomers to experimental results of the full polymer system made interpretation of the results difficult. We hypothesize that comparing our DFT calculations directly to the results for small oligomers will allow a better assessment of the agreement between calculation and experiment. It is important to determine what functionals are suitable if DFT calculations are to be used to guide solar cell design. In Aim 1, we will determine which functionals adequately model oligomers that contain silicon and germanium as central atoms (rather than the more common carbon). In Aim 2, we will determine the true extent of charge delocalization by comparing results for oligomers that span the range suggested for delocalization lengths. At the conclusion of this work, we will have expanded knowledge of how to model electron donating systems and provided tools that can be used to model newly developed solar devices which will make such devices more economically viable and reduce our reliance on fossil fuels.