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

主要研究者：马洪提案编号：1236272机构：华盛顿大学职称：高性能太阳能电池的分子环境定制、自组装和纳米形态控制的电子受体到目前为止，构建聚合物太阳能电池（PSC）的最有效结构是通过混合富电子聚合物和缺电子富勒烯化合物制备的本体异质结（BHJ）结构，例如[6，6]-苯基-C61（或C71）丁酸甲酯（PCBM），其能量转换效率超过8%。然而，富勒烯衍生物具有不期望的性质，例如相对大的带隙和在可见光谱中的低吸收系数，从而缺乏对太阳辐射的理想吸收，以及过深的LUMO能级，从而导致电子转移期间不必要的能量损失，并因此限制最终器件的效率，特别是它们的开路电压。因此，迫切需要替代受体材料，如PCBM，具有良好的电子传输和加工性能，但也强烈吸收太阳光谱，具有与富勒烯受体明显不同的能级，并表现出衍生化和功能化的多样化。此外，期望具有电子受体，其具有可调分子结构、电子供体（D）/受体（A）共混物中的受控纳米形态和优化器件架构中的定制D/A界面的组合，这允许最大化激子产生/迁移和电荷分离/传输/收集。本计画的主要目标为：1）透过调整π共轭核/桥及周边基团，发展具有可调能量的电子受体（带隙，HOMO，LUMO），控制分子介电，偶极和空间环境以有利于有效的D/A界面电荷分离，并引入热/光可去除的，氢键和表面结合基团以允许可加工性，单层模板自组装和纳米相形成，用于优化电荷传输和收集; 2）对这些电子受体在溶液/薄膜及其与可变比率的低带隙p型聚合物的共混物中的物理、电子和形态学研究，以及建立分子结构与材料性质（例如光吸收）之间的相关性，电子性质、光致发光猝灭和电荷分离/传输依赖于分子环境和纳米相控制; 3）通过利用优化的电子受体作为有源层的组分，通过旋转浇铸本体异质结或图案化单层诱导的D/A纳米相组装，制造和测试常规和倒置PSC器件，以获得高于10%的高功率转换效率和良好的稳定性。具有可调控的分子环境、自组装特性和可控纳米相的新型电子受体的合成和加工，以及它们的器件制备和测试，将为满足这些要求提供一种变革性的途径，并为从根本上理解分子结构、加工和性能之间的关系建立一个新的平台，特性和器件性能，特别是取决于介电、偶极和空间参数的D/A界面电荷分离。 该项目将通过培训新的专业人员产生广泛的影响，这些专业人员掌握最先进的研究技术，具有明智性，创造性，并致力于解决社会需求。该项目将包括从幼儿园到12年级直至研究生的各级教育活动。

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.