Xie Xingyu, Chen Zhiyun, Zheng Shaohui
School of Materials and Energy Southwest University, 2nd Tiansheng Road, Beibei District, Chongqing 400715, China.
J Phys Chem A. 2025 Mar 27;129(12):2866-2875. doi: 10.1021/acs.jpca.4c08587. Epub 2025 Mar 13.
With the application of nonfullerene acceptors (NFAs) Y6 and its derivatives, the power conversion efficiencies (PCEs) of single-junction organic solar cells (OSCs) have exceeded 20%. Side-chain engineering has proven to be an important strategy for optimizing Y6-based NFAs. However, studies on the incorporation of conjugated side chains into Y6-based NFAs are still rare, and the corresponding underlying mechanisms are still not well understood. In this article, we systematically designed eight molecules based on modifications to the conjugated side chains of two reported Y6-based NFAs, involving alterations of branched alkyl chains at different positions on the thiophene, benzene, bithiophene, and benzene-thiophene moieties that serve as conjugated side chains. Using reliable density functional theory (DFT) and time-dependent DFT calculations, we obtained key photovoltaic parameters such as molecular planarity, dipole moments, electrostatic potential and corresponding fluctuations, frontier molecular orbitals, exciton binding energy (), singlet-triplet energy differences (Δ), and UV-vis absorption spectra of these newly designed NFAs. The results show that the side conjugated rings and the positions of lateral alkyl chains attached to these rings exert noticeable influences on their photoelectric properties. Notably, compared to the prototype T3EH, 2T2EH, 2T3EH, PT2EH, PT3EH, and P2EH exhibit enhanced absorption (manifesting as increased total oscillator strength) and smaller and Δ values, hinting at their promising potential as novel NFAs.
随着非富勒烯受体（NFAs）Y6及其衍生物的应用，单结有机太阳能电池（OSCs）的功率转换效率（PCEs）已超过20%。侧链工程已被证明是优化基于Y6的NFAs的重要策略。然而，关于将共轭侧链引入基于Y6的NFAs的研究仍然很少，相应的潜在机制仍未得到很好的理解。在本文中，我们基于对两种已报道的基于Y6的NFAs的共轭侧链的修饰，系统地设计了八个分子，涉及噻吩、苯、联噻吩和苯并噻吩部分上不同位置的支链烷基链的改变，这些部分用作共轭侧链。使用可靠的密度泛函理论（DFT）和含时DFT计算，我们获得了这些新设计的NFAs的关键光伏参数，如分子平面性、偶极矩、静电势及其相应波动、前沿分子轨道、激子结合能（）、单重态-三重态能量差（Δ）和紫外-可见吸收光谱。结果表明，侧共轭环以及连接到这些环上的侧链烷基的位置对其光电性能有显著影响。值得注意的是，与原型T3EH相比，2T2EH、2T3EH、PT2EH、PT3EH和P2EH表现出增强的吸收（表现为总振子强度增加）以及更小的和Δ值，这暗示它们作为新型NFAs具有潜在的应用前景。
