Molecular weight is an important factor determining the morphology and performance of all‐polymer solar cells. Through the application of direct arylation polycondention, a series of batches of a fluorinated naphthalene diimide‐based acceptor polymer are prepared with molecular weight varying from M_n = 20 to 167 kDa. Used in conjunction with a common low bandgap donor polymer, the effect of acceptor molecular weight on solar cell performance, morphology, charge generation, and transport is explored. Increasing the molecular weight of the acceptor from M_n = 20 to 87 kDa is found to increase cell efficiency from 2.3% to 5.4% due to improved charge separation and transport. Further increasing the molecular weight to M_n = 167 kDa however is found to produce a drop in performance to 3% due to liquid–liquid phase separation which produces coarse domains, poor charge generation, and collection. In addition to device studies, a systematic investigation of the microstructure and photophysics of this system is presented using a combination of transmission electron microscopy, grazing‐incidence wide‐angle X‐ray scattering, near‐edge X‐ray absorption fine‐structure spectroscopy, photoluminescence quenching, and transient absorption spectroscopy to provide a comprehensive understanding of the interplay between morphology, photophysics, and photovoltaic performance.

中文翻译：

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调整全聚合物太阳能电池中电子接受聚合物的分子量：对形态和电荷产生的影响

分子量是决定全聚合物太阳能电池的形态和性能的重要因素。通过直接芳基化缩聚反应的应用，制备了一系列批次的氟化萘二酰亚胺基受体聚合物，分子量从M _n = 20至167 kDa。与常见的低带隙供体聚合物结合使用，探索了受体分子量对太阳能电池性能，形态，电荷产生和传输的影响。由于改善的电荷分离和运输，发现受体的分子量从M _n = 20增加到87 kDa使电池效率从2.3％增加到5.4％。进一步增加分子量至M _n但是，由于液相之间的分离会产生粗糙的磁畴，不良的电荷产生和收集，因此= 167 kDa的性能会降低至3％。除装置研究外，还结合透射电子显微镜，掠入射宽角X射线散射，近边缘X射线吸收精细结构光谱对系统的微观结构和光物理进行了系统研究。光致发光猝灭和瞬态吸收光谱法可提供对形态，光物理和光伏性能之间相互作用的全面了解。