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Branched alkyl-chain engineering of chlorinated asymmetrical acceptors for improved organic photovoltaic performance
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2022-09-13 , DOI: 10.1039/d2ta05846d
Dandan Li 1 , Gang Li 1 , Zhixiang Li 2 , Lingxian Meng 2 , Yan Xu 1 , Guanwei Cui 1 , Yunfei Bai 1 , Xiangjian Wan 2 , Yongsheng Chen 2 , Bo Tang 1
Affiliation  

Side chains generally dictate molecular packing and film morphology and critically affect the efficiency of organic solar cells (OSCs), and hence, side-chain engineering plays a substantial role in achieving high-performance OSCs. In this work, a series of non-fullerene acceptor molecules with A–D–A structures, L6–L11, having gradient branched alkyl-chains on dithieno[3,2-b:2′,3′-d]pyrrole (DTP)-based asymmetrical chlorinated acceptors were designed and synthesized. The effects of branched alkyl-chain length, ranging from n-butyl to 2-decyldodecyl chains, on their optoelectronic properties, thin film molecular packing, blend film morphology and overall photovoltaic performance were systematically studied. Interestingly, the results indicated that with the increase in alkyl-chain length, the open-circuit-voltage (VOC) is monotonously increased, while the short-circuit current density (JSC), fill factor (FF) and power conversion efficiencies (PCEs) perceive a distinct parabolic trend. The reasons for the variation trend of photoelectric parameters were analyzed. Finally, a 2-butyloctyl chain-containing acceptor L8-based device demonstrated a champion PCE of 15.40% with a VOC of 0.864 V, a JSC of 23.63 mA cm−2 and an FF of 0.754, which is the highest PCE for non-fullerene binary OSCs based on asymmetric ITIC-type acceptors. Further studies indicate that the proper 2-butyloctyl side chain could induce more favorable face-on molecule orientation, enhance carrier mobility, balance charge transport and suppress recombination loss. Our results will provide valuable guidelines for accelerating the understanding of the acceptor structure-photovoltaic performance relationship of OSC materials.

中文翻译:

用于改善有机光伏性能的氯化不对称受体的支链烷基链工程

侧链通常决定分子堆积和薄膜形态,并严重影响有机太阳能电池 (OSC) 的效率,因此,侧链工程在实现高性能 OSC 方面发挥着重要作用。在这项工作中,一系列具有 A-D-A 结构的非富勒烯受体分子 L6-L11,在二噻吩并[3,2- b :2',3' - d ]吡咯(DTP ) 为基础的不对称氯化受体设计和合成。支链烷基链长度的影响,范围从n系统研究了-丁基到2-癸基十二烷基链的光电性能、薄膜分子堆积、共混膜形态和整体光伏性能。有趣的是,结果表明随着烷基链长度的增加,开路电压(V OC)单调增加,而短路电流密度(J SC)、填充因子(FF)和功率转换效率(PCE) 感知到明显的抛物线趋势。分析了光电参数变化趋势的原因。最后,基于 2-丁基辛基链的受体 L8 器件展示了 15.40% 的冠军 PCE,V OC为 0.864 V,J SC23.63 mA cm -2和 0.754 的 FF,这是基于不对称 ITIC 型受体的非富勒烯二元 OSC 的最高 PCE。进一步的研究表明,适当的 2-丁基辛基侧链可以诱导更有利的正面分子取向,增强载流子迁移率,平衡电荷传输并抑制重组损失。我们的研究结果将为加速理解 OSC 材料的受体结构-光伏性能关系提供有价值的指导。
更新日期:2022-09-13
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