Wu Xiangxi, Gong Yufei, Li Xiaojun, Qin Shucheng, He Haozhe, Chen Zekun, Liang Tongling, Wang Caixuan, Deng Dan, Bi Zhaozhao, Ma Wei, Meng Lei, Li Yongfang
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
School of Chemical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
Angew Chem Int Ed Engl. 2025 Jan 21;64(4):e202416016. doi: 10.1002/anie.202416016. Epub 2024 Nov 2.
Organic solar cells (OSCs) processed with non-halogenated solvents usually suffer from excessive self-aggregation of small molecule acceptors (SMAs), severe phase separation and higher energy loss (E), leading to reduced open-circuit voltage (V) and power conversion efficiency (PCE). Regulating the intermolecular interaction to disperse the aggregation and further improve the molecular packing order of SMAs would be an effective strategy to solve this problem. Here, we designed and synthesized two SMAs L8-PhF and L8-PhMe by introducing different substituents (fluorine for L8-PhF and methyl for L8-PhMe) on the phenyl end group of the inner side chains of L8-Ph, and investigated the effect of the substituents on the intermolecular interaction of SMAs, E and performance of OSCs processed with non-halogenated solvents. Through single crystal analysis and theoretical calculations, it is found that compared with L8-PhF, which possesses strong and abundant intermolecular interactions but downgraded molecular packing order, L8-PhMe with the methyl substituent possesses more effective non-covalent interactions, which improves the tightness and order of molecular packing. When blending the SMAs with polymer donor PM6, the differences in intermolecular interactions of the SMAs influenced the film formation process and phase separation of the blend films. The L8-PhMe based blend film exhibits shorten film formation and more homogeneous phase separation than those of the L8-PhF and L8-Ph based ones. Especially, the OSCs based on L8-PhMe show reduced non-radiative energy loss and enhanced V than the devices based on the other two SMAs. Consequently, the L8-PhMe based device processed with o-xylene (o-XY) and using 2PACz as the hole transport layer (HTL) shows an outstanding PCE of 19.27 %. This study highlights that the E of OSCs processed with non-halogenated solvents could be decreased through regulating the intermolecular interactions of SMAs by inner side chain modification, and also emphasize the importance of effectivity rather than intensity of non-covalent interactions introduced in SMAs on the molecular packing, morphology and PCE of OSCs.
用非卤化溶剂加工的有机太阳能电池（OSC）通常会受到小分子受体（SMA）过度自聚集、严重相分离和较高能量损失（E）的影响，导致开路电压（V）和功率转换效率（PCE）降低。调节分子间相互作用以分散聚集并进一步改善SMA的分子堆积顺序将是解决这一问题的有效策略。在此，我们通过在L8-Ph内侧链的苯基端基上引入不同的取代基（L8-PhF为氟，L8-PhMe为甲基），设计并合成了两种SMA：L8-PhF和L8-PhMe，并研究了取代基对SMA分子间相互作用、E以及用非卤化溶剂加工的OSC性能的影响。通过单晶分析和理论计算发现，与具有强而丰富的分子间相互作用但分子堆积顺序降低的L8-PhF相比，具有甲基取代基的L8-PhMe具有更有效的非共价相互作用，这改善了分子堆积的紧密性和有序性。当将SMA与聚合物供体PM6共混时，SMA分子间相互作用的差异影响了共混膜的成膜过程和相分离。基于L8-PhMe的共混膜比基于L8-PhF和L8-Ph的共混膜表现出更短的成膜时间和更均匀的相分离。特别是，基于L8-PhMe的OSC比基于其他两种SMA的器件表现出更低的非辐射能量损失和更高的V。因此，用邻二甲苯（o-XY）加工并使用2PACz作为空穴传输层（HTL）的基于L8-PhMe的器件表现出19.27%的出色PCE。这项研究强调，通过内侧链修饰调节SMA的分子间相互作用，可以降低用非卤化溶剂加工的OSC的E，同时也强调了SMA中引入的非共价相互作用的有效性而非强度对OSC的分子堆积、形态和PCE的重要性。
