Fluolab【Angew.Chem.】安徽师范大学史永强、常州大学宋欣|突破20.5%效率大关！同分异构固体添加剂助力有机太阳电池性能飞跃
文章标题： Isomerized Dithienopyrazine-Based Solid Additive Enables Organic Solar Cells With 20.5% Efficiency
通讯作者： Xin Song, Yongqiang Shi
文章概要
引言
有机太阳电池（OSCs） 凭借其成本低、柔性好以及可大面积制备等独特优势，已成为光伏领域的研究热点。随着新型给体和受体材料的不断涌现，其能量转换效率（PCE）已成功突破20%。在这一过程中，活性层形貌的精准调控至关重要，它直接决定了激子解离和电荷传输的效率。虽然传统的液体添加剂在优化形貌方面效果显著，但其高沸点导致的残留问题往往会损害器件的长期稳定性。相比之下，挥发性固体添加剂因其能够有效调节分子间相互作用且易于去除，受到了研究者的广泛关注。然而，目前关于固体添加剂的分子结构，尤其是同分异构效应如何调控分子堆积和形貌形成的深层机制仍有待深入挖掘。
(a) Representative examples of previously reported isomeric solid additives based on halogen-substituted positional isomerism and linkage positional isomerism. (b) Molecular structures of the dithienopyrazine-based isomeric additives investigated in this work: syn-DTPy and anti-DTPy.
主要实验及结论
本研究创新性地提出了一种基于芳香环并环异构化的固体添加剂策略。研究团队设计并合成了两种基于二噻吩并吡嗪（DTPy）核心的同分异构体：syn-DTPy和anti-DTPy。热重分析表明两者均具有良好的挥发性，确保了在成膜过程中的加工灵活性。通过紫外-可见吸收光谱观察到，相比于对照组，经anti-DTPy处理的薄膜表现出明显的红移和增强的振动峰，这预示着分子间形成了更加有序的H-聚集态堆积。理论计算和分子动力学模拟进一步证实，由于静电势分布（ESP） 的差异，anti-DTPy能与受体材料L8-BO产生更强的定向相互作用，引导活性层向热力学更稳定的低能量构型演变，从而抑制了过度聚集带来的负面影响。
(a) Chemical structures of D18, L8-BO, and isomeric solid additives of syn-DTPy and anti-DTPy. (b) TGA curves of syn-DTPy and anti-DTPy. (c, d) UV–Vis absorption spectra of D18 films treated with/without the isomeric additives and L8-BO films treated with/without the isomeric additives.
The strongest conformations and calculated binding energies for the complexes of (a) D18:syn-DTPy and L8-BO:syn-DTPy, (b) D18:anti-DTPy and L8-BO:anti-DTPy. The final state molecular diagrams of the D18:L8-BO system with solid additives of (c) syn-DTPy and (d) anti-DTPy, which were performed by the molecular dynamics (MD) simulation using the COMPASSII force field based on the Andersen thermostat. (e) Total intermolecular interactions (including van der Waals interaction and electrostatic interaction) between D18:L8-BO and syn-DTPy or anti-DTPy molecules. (f) Radial distribution function (RDF) analysis of molecular packing.
(a) J–V characteristics of the D18:L8-BO-based OSCs processed without or with solid additives. (b) EQE spectra of the control and syn-DTPy/anti-DTPy-processed OSCs. (c) Plots of the PCE as a function of and FF for isomeric solid additives-processed binary OSC reported over the preceding years. (d) TPC and (e) TPV decay curves. (f) Electron and hole mobility of devices with/without solid additives.
在光伏性能测试中，基于D18:L8-BO体系的器件在加入anti-DTPy后展现出惊人的表现。实验结果显示，该器件实现了20.5%的超高光电转换效率，其填充因子（FF）高达81.9%，短路电流密度也有显著提升。瞬态光电流（TPC）和瞬态光电压（TPV）测试表明，anti-DTPy处理后的器件具有更短的电荷提取时间和更长的载流子寿命，意味着双分子复合得到了显著抑制。此外，空间电荷限制电流（SCLC）法测得的空穴和电子迁移率更加平衡，这归功于添加剂诱导形成的紧凑且高度结晶的Face-on取向堆积。飞秒瞬态吸收光谱也从动力学角度证明，anti-DTPy加速了激子在界面处的解离和空穴转移过程。最后，该策略在多个主流给受体体系中均表现出优异的普适性。
The charge carrier density as a function of the delay time of the D18:L8-BO (a), syn-DTPy (b), and (c) anti-DTPy devices. (d) Represent linear fits to the measured data points, with the recombination orders λ indicated in the graph. (e) The trap DOS curves of the D18:L8-BO control, syn-DTPy, and anti-DTPy devices. (f) Kinetic traces of D18:L8-BO control, syn-DTPy, and anti-DTPy devices at the selected wavelength.
(a) AFM height images of the control, syn-DTPy-treated, and anti-DTPy-treated D18:L8-BO blend films. (b) 2D-GIWAXS patterns of the D18:L8-BO blend films, syn-DTPy-treated, and anti-DTPy-treated blend films. (c) 2D-GIWAXS line-cut profiles in the OOP and IP directions for the D18:L8-BO control, syn-DTPy-treated, and anti-DTPy-treated blend films.
总结及展望
这项工作成功展示了通过分子异构化设计精准调控活性层形貌的巨大潜力。研究发现，anti-DTPy作为一种高效的固体添加剂，能够协同优化给体和受体的结晶行为，构建出理想的互穿网络结构，从而大幅提升器件的效率和电荷传输特性。20.5%的效率纪录不仅刷新了二元有机太阳电池的性能上限，也为未来开发高性能光伏材料提供了全新的结构设计思路。这一发现强调了分子拓扑结构在形貌工程中的核心地位，预示着基于芳香环并环异构的调控手段将成为推动有机光伏技术工业化进程的重要利器。