Chain aggregation dictates bimolecular charge recombination and fill factor of all-polymer blend solar cells,Journal of Materials Chemistry A

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Chain aggregation dictates bimolecular charge recombination and fill factor of all-polymer blend solar cells
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2022-09-30 , DOI: 10.1039/d2ta04705e
Ren Hagio ₁ , Hiroaki Benten ₁ , Yunju Na ₁ , Zhiyuan Liang ₁ , Naoki Oyaizu ₁ , Junya Suzuki ₁ , Shota Kubota ₁ , Min-Cherl Jung ₁ , Hirotaka Kojima ₁ , Masakazu Nakamura ₁

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One of the bottlenecks in improving power conversion efficiencies of all-polymer blend solar cells is the low fill factor (FF), along with the intolerance to film thickness. In this study, we examined the behavior of charge-carrier extraction and recombination to determine the key factors that improve or limit the FFs of all-polymer blend solar cells. We conducted space-charge-limited current mobility, electrical impedance spectroscopy, and grazing-incidence wide-angle X-ray scattering measurements for four exemplary all-polymer blend devices composed of a naphthalene diimide-based low-bandgap polymer acceptor. The high charge-carrier collection ability and, thus the high FF of ∼70% of the all-polymer blends result from the long charge-carrier lifetime due to small bimolecular recombination coefficients. The degree of suppression of the bimolecular charge recombination is quantified using the Langevin theory and is then related to the blend morphology of the device. Consequently, we conclude that the preferred blend morphology for suppressing bimolecular recombination is characterized by a well-ordered local structure due to chain aggregation by both the polymer donor and acceptor. This study guides future research efforts toward the development of thickness-tolerant all-polymer-blend solar cells with high FFs.

中文翻译：

链聚集决定了全聚合物混合太阳能电池的双分子电荷复合和填充因子

提高全聚合物混合太阳能电池的功率转换效率的瓶颈之一是低填充因子 (FF)，以及对薄膜厚度的不耐受。在这项研究中，我们检查了电荷载流子提取和重组的行为，以确定改善或限制全聚合物共混太阳能电池 FF 的关键因素。我们对由萘二亚胺基低带隙聚合物受体组成的四种示例性全聚合物共混器件进行了空间电荷限制电流迁移率、电阻抗光谱和掠入射广角 X 射线散射测量。高载流子收集能力以及全聚合物共混物的 70% 的高 FF 是由于双分子复合系数小而导致的长载流子寿命。双分子电荷复合的抑制程度使用朗之万理论进行量化，然后与器件的共混形态相关。因此，我们得出结论，用于抑制双分子重组的优选共混物形态的特征在于由于聚合物供体和受体的链聚集而具有良好有序的局部结构。这项研究指导未来的研究工作，以开发具有高 FF 的耐厚度全聚合物混合太阳能电池。

更新日期：2022-09-30

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