Optical, Electrical and Magnetic Studies of pi-Conjugated Polymer/Organic Acceptor Blends for Photovoltaic Applications

技术：该项目旨在更好地理解PCP （p-共轭聚合物）与分子受体共混物中的电子态、电荷输运和自旋现象，这些分子受体用于大块异质结OPV（有机光伏）器件。在共混物（薄膜和器件）中研究的过程/现象包括：超快激子解离、电荷产生机制、间隙下响应、PCP链和受体分子的电荷转移复合物（CTC）的形成、孪晶重组、依赖自旋的传输和重组以及依赖形态的载流子迁移率。这些研究将在具有高OPV效率的不同浓度的pcp -富勒烯共混物以及以前未使用过的新型pcp -受体共混物中进行。研究结果有望有助于对OPV设备中控制光伏响应的物理过程的基本理解，并有可能将其太阳能转换效率提高到超过目前6%的记录。该方法利用光学、电学和磁学实验技术：(i)将使用泵浦/探针光电调制（PM）技术在0.1至2.5 eV的光谱范围内研究混合物中的超快激子和极化子动力学；（ii） (i)中的激发从上到下间隙光子能量变化，以探索除传统的从聚合物链到受体分子的电荷转移之外，通过其他过程产生极化子的可能性；（iii）通过红外光致发光、间隙下吸收、红外电吸收和光生极化子作用光谱研究共混物中CTC态的可能形成；（iv）电导纳光谱，用于获得载流子迁移率；(v)用于极化子复合研究的OPV器件的磁阻测量；（vi）光学检测自旋1 / 2极化子的磁共振动力学，用于研究OPV器件中自旋相关的复合和自旋晶格弛豫率。非技术性：项目涉及电子/光子材料科学领域的基础研究问题，具有较高的技术相关性。这些研究可能会导致提高太阳能转换效率的OPV（有机光伏）器件，并加深我们对pcp -受体共混物的理解。此外，整合实验工作，包括聚合物和小分子合成、光学、磁输运、建模、器件制造、加工和测试，将有助于培养研究生和本科生，以及一名博士后，他将参与这个跨学科的研究项目。研究生课程是什么？有机光电子学;基础研究和设备应用？也是计划中的。推广计划包括高中生和他们的导师在夏季参与研究，以及向公众展示有机发光二极管和OPV设备的工程演示。

Technical: This project aims for greater understanding of electronic states, charge transport, and spin phenomena in blends of PCP (p-conjugated polymers) with molecular acceptors that are used in bulk-heterojunction OPV (organic photovoltaic) devices. Processes/phenomena to be investigated in blends (films and devices) include: ultrafast exciton dissociation, charge generation mechanism, below-gap response, formation of charge transfer complex (CTC) of PCP chains and acceptor molecules, geminate recombination, spin-dependent transport and recombination, and morphology-dependent carrier mobility. These studies will be conducted in PCP-fullerene blends of different concentrations that show high OPV efficiency, as well as in novel PCP-acceptor blends that have not been used before. Outcomes are expected to contribute to basic understanding of physical processes that govern photovoltaic response in OPV devices, and have potential to increase their solar power conversion efficiency beyond the 6% record of the present time. The approach utilizes optical, electrical and magnetic experimental techniques: (i) ultrafast exciton and polaron dynamics in the blends will be investigated using a pump/probe photomodulation (PM) technique in the spectral range of 0.1 to 2.5 eV; (ii) the excitation in (i) is to vary from above to below-gap photon energy to explore the possibility of polaron generation by processes other than traditional charge transfer from the polymer chain onto the acceptor molecule; (iii) the possible formation of a CTC state in the blends will be studied by IR-photoluminescence, below-gap absorption, IR-electroabsorption, and photogenerated polaron action spectra; (iv) electrical admittance spectroscopy for obtaining the carrier mobilities; (v) magnetoresistance measurements of OPV devices for studying polaron recombination; and (vi) dynamics of optically-detected magnetic-resonance of spin ½ polarons for studying spin-dependent recombination, and spin-lattice relaxation rate in OPV devices. Non-technical: The project addresses basic research issues in a topical area of electronic/photonic materials science with high technological relevance. These studies may lead to OPV (organic photovoltaic) devices with enhanced solar power conversion efficiency, and deepen our understanding of the PCP-acceptor blends. In addition, the integration of experimental efforts, including polymer and small molecule synthesis, optics, magneto-transport, modeling, and device fabrication, processing and testing, will serve to educate graduate and undergraduate students, and a postdoctoral associate who will be involved in this interdisciplinary research project. A graduate course on ?Organic optoelectronics; basic studies and device applications? is also planned. An outreach program includes research participation of high school students and their teacher mentors during the summer, as well as engineering demonstrations for illustrating organic light emitting diodes and OPV devices to the public.