Molecular Environment-Tailored, Self-Assembled and Nanomorphology-Controlled Electron Acceptors for High-Performance Solar Cells

项目编号：1236272单位：华盛顿大学到目前为止，构建聚合物太阳能电池（PSCs）最有效的结构是由富电子聚合物和缺电子的富勒化物(如[6,6]-苯基- c61（或C71）丁酸甲酯（PCBMs）混合制备的体异质结（BHJ）结构，其功率转换效率超过8%。然而，富勒烯衍生物有一些不理想的特性，如在可见光谱中相对较大的带隙和较低的吸收系数，对太阳辐射缺乏理想的吸收，并且过深的LUMO能级导致电子转移过程中不必要的能量损失，从而限制了最终器件的效率，特别是它们的开路电压。因此，迫切需要一种替代受体材料，如pcbm，具有良好的电子传输和加工性能，但也具有强烈的太阳光谱吸收，具有与富勒烯基受体显著不同的能级，并且在衍生化和功能化方面表现出多样化。此外，希望电子受体具有可调分子结构的组合，电子供体(D)/受体(A)混合物中的纳米形态可控，以及优化器件架构中的定制D/A接口，从而最大限度地实现激子产生/迁移和电荷分离/传输/收集。该项目的主要目标是：1)通过定制π共轭核心/桥和外围基团来开发电子受体，使其具有可调的能量（带隙，HOMO， LUMO），控制分子介电，偶极和立体环境，以促进有效的D/A界面电荷分离，并引入热/光可去除，氢键和表面结合基团，以允许可加工性；用于优化电荷传输和收集的单层模板自组装和纳米相形成2)对这些电子受体在溶液/薄膜及其与低带隙p型聚合物共混物中的光物理、电子和形态进行了研究，建立了依赖于分子环境和纳米相控制的分子结构与材料性质（如光吸收、电子性质、光致发光猝灭、电荷分离/输运等）之间的相关性；3)利用优化后的电子受体作为有源层，通过自旋铸造体异质结或图形化单层诱导组装D/A纳米相，制备和测试传统和倒置PSC器件，实现10%以上的高功率转换效率和良好的稳定性。合理设计、合成和加工具有可定制分子环境、自组装性能和可控纳米相的新型电子受体及其器件的制造和测试将为满足这些要求提供一种变革性的方法，并为从基础上理解分子结构、加工、性能和器件性能之间的关系，特别是依赖介电的D/ a界面电荷分离，建立一个新的平台。偶极和空间参数。该项目将通过培养具有最先进的研究技术、明智、创新和致力于解决社会需求的新专业人员，产生广泛的影响。该项目将包括从K-12到研究生的不同层次的教育活动。

PI: Ma, HongProposal Number: 1236272Institution: University of WashingtonTitle: Molecular Environment-Tailored, Self-Assembled and Nanomorphology-Controlled Electron Acceptors for High-Performance Solar CellsSo far, the most efficient architecture to build polymeric solar cells (PSCs) is the bulk heterojunction (BHJ) structure prepared by mixing electron-rich polymers and electron-deficient fullerides such as [6,6]-phenyl-C61 (or C71) butyric acid methyl ester (PCBMs) with a power-conversion efficiency of over 8%. However, fullerene derivatives have undesirable properties such as a relatively large bandgap and low absorption coefficient in the visible spectrum to lack ideal absorption of solar radiation, and excessively deep lying LUMO level to result in needless energy loss during electron transfer and so limit the efficiencies of the final devices, in particular their open-circuit voltages. Thus, there is an urgent need for alternative acceptor materials that - like PCBMs - possess favorable electron-transporting and processing properties, but which also absorb strongly in the solar spectrum, have energy levels significantly different from those of fullerene-based acceptors, and exhibit diversification regarding derivatization and functionalization. In addition, it is desirable to have electron acceptors with the combination of tunable molecular structures, controlled nanomorphology in electron donor (D)/acceptor (A) blends, and tailored D/A interfaces in optimized device architectures, which allow maximized exciton generation/migration and charge separation/transport/collection. The main objectives of this project are 1) development of electron acceptors through tailoring of pi-conjugated core/bridge and peripheral group to have tunable energetics (bandgap, HOMO, LUMO), controlling molecular dielectric, dipolar and steric environment to favor efficient D/A interfacial charge separation, and introducing thermo-/photo-removable, hydrogen-bonding and surface-binding groups to allow processability, monolayer-templated self- assembly and nanophase formation for optimized charge transport and collection; 2) photophysical, electronic and morphological studies of these electron acceptors in solution/thin film and their blends with variable ratios of low-bandgap p-type polymers, and establishment of a correlation between molecular structures and material properties such as light absorption, electronic property, photoluminescence quenching, and charge separation/transport dependent on molecular environment and nanophase control; 3) fabrication and testing of conventional and inverted PSC devices by utilizing optimized electron acceptors as component of active layer through spin-cast bulk heterojunction or patterned monolayer-induced assembly of D/A nanophases toward high power-conversion efficiency above 10% and good stability.Rational design, synthesis and processing of novel electron acceptors with tailorable molecular environment, self- assembling property and controlled nanophase, and their device fabrication and testing will provide a transformative approach to fulfill these requirements, and establish a new platform in fundamental understanding of relationship among molecular structure, processing, property and device performance in particular on D/A interfacial charge separation dependent on dielectric, dipolar and steric parameters. This project will have broad impact through the training of new professionals who are skilled with state-of-the-art research techniques and are sensible, creative, and devoted to solve the social need. This project will include education activities at different levels covering K-12 to graduate students.