【作者】 张铭；

【导师】 张志国；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2025， 博士

【摘要】 通过溶液加工,有机太阳能电池能够低成本的大面积制备具有轻、薄、柔特点的光伏电池薄膜,在可穿戴设备,光伏建筑一体化,室内光伏和物联网等方面有广泛的应用前景,是现行光伏技术的有力补充。近年来,得益于分子结构设计和器件制备工艺的持续优化,有机太阳能电池的能量转换效率已超过20%,达到了商业化应用的阈值。但要实现商业化应用,高性能有机太阳能电池在工作条件下的长期稳定性不佳仍是亟待解决的问题。其中本体异质结活性层的形貌涉及相分离与混合之间的微妙平衡,是影响器件稳定性的关键因素。为了获得最佳的器件性能,器件制备中,活性层形貌一般被冻结在热力学非平衡态。因此,确保该形貌在器件运行过程中相互混合程度和分子堆积状态保持不变,对于保持器件的稳定性非常重要。然而由于小分子受体的玻璃化转变温度较低,其活性层在持续光照和外界应力的作用下容易发生热力学松弛,导致过度相分离和纯化,使得器件效率降低。为此,本论文针对有机太阳能电池中效率与稳定性难以协同提升的难题,提出了柔性链连接受体分子的寡聚化设计策略。通过提升受体的玻璃化转变温度,抑制活性层中受体分子的扩散行为,构建动力学稳定的活性层形貌。同时,通过精细调控链接受体的结构,实现了器件效率与稳定性的同步优化。主要研究成果可归纳如下:1. 设计合成了一类基于Y6受体的新型链接二聚体受体,并考察了不同长度的柔性链对二聚体的聚集和松弛行为以及光伏性能的调控。其中,基于辛基链的DY2共混体系的开路电压和能量转换效率分别达到0.87 V和17.85%,而基于Y6受体的器件的开路电压和效率分别仅为0.84 V和16.93%。更重要的是,链接二聚体受体表现出较高的玻璃化转变温度,能够有效抑制共混相中的热力学松弛。基于链接二聚体受体的器件在连续光照700小时后,仍能保持超过80%的初始效率,表现出显著降低的初始效率损失。这种设计合成链接寡聚体受体的新方法为开发高效率且具有优异运行稳定性的有机太阳能电池提供了新的方向。2. 本章针对共轭侧链修饰的链接寡聚受体DY-P2EH与聚合物给体之间互溶性不足导致的过度相分离这一特点,提出了一种基于热力学调控的三元共混策略。即通过引入与聚合物给体具有良好混溶性的小分子受体BTP-eC9作为第三组分,巧妙利用DY-P2EH和BTP-eC9两种受体在热力学上的显著差异,成功构建了多层次相分离结构。研究表明:(1)高混溶性的BTP-eC9受体在体系中自发形成三维连续的互穿网络结构,显著改善了激子解离效率;(2)低混溶性的DY-P2EH二聚体作为"锚定点",有效抑制了小分子受体的聚集和迁移。这种协同作用机制使得三元体系在获得优异的光伏性能(填充因子80.61%,能量转换效率19.09%)的同时,展现出优异的热稳定性(在85℃加速老化测试1100小时后,器件效率衰减率低于15%)。3. 本章提出了一种异质链接受体分子的设计策略,通过柔性链将明星受体分子Y6与L8BO共价连接,成功构建了新型寡聚受体DY-L。我们通过实验和理论计算,深入研究了该异质链接结构对材料热力学性质、动力学行为以及器件性能的影响机制。研究发现,这种分子内异质链接策略实现了Y6和L8BO两种受体分子在分子尺度上的精准混合,与传统的物理共混体系相比,DY-L表现出以下显著优势:(1)通过分子内电荷转移效应优化了光电响应特性;(2)调控了分子间π-π堆积行为,形成了更有序的分子排列;(3)显著改变了溶液预聚集状态,为活性层形貌调控提供了新的途径。基于DY-L的器件在表现出优异稳定性的同时,取得了高达20.54%的能量转换效率,这是目前基于寡聚物的二元有机太阳能电池的最高值。更多还原

【Abstract】 Through solution processing,organic solar cells（OSCs）can be fabricated into large-area,lightweight,thin,and flexible photovoltaic films at low cost,demonstrating broad application prospects in wearable devices,building-integrated photovoltaics（BIPV）,indoor photovoltaics,and the Internet of Things（Io T）.These characteristics make OSCs a strong complement to existing photovoltaic technologies.In recent years,thanks to continuous optimization of molecular design and device fabrication processes,the power conversion efficiency（PCE）of OSCs has surpassed 20%,reaching the threshold for commercial applications.However,to achieve commercialization,the poor long-term stability of high-performance OSCs under operating conditions remains a critical issue to be addressed.The morphology of the bulk heterojunction（BHJ）active layer,which involves a delicate balance between phase separation and mixing,is a key factor affecting device stability.To achieve optimal device performance,the active layer morphology is typically frozen in a thermodynamically non-equilibrium state during fabrication.Therefore,maintaining the degree of intermixing and molecular packing in the active layer during device operation is crucial for ensuring stability.However,due to the low glass transition temperature（Tg）of small-molecule acceptors（SMAs）,the active layer is prone to thermodynamic relaxation under continuous illumination and external stress,leading to excessive phase separation and purification,which degrades device efficiency.To address the challenge of simultaneously improving efficiency and stability in OSCs,this thesis proposes a tethered small molecule acceptors（TSMAs）design strategy with flexible linkers.By increasing the Tg of the acceptors,this approach suppresses the diffusion behavior of acceptor molecules in the active layer,thereby constructing a kinetically stable morphology.Meanwhile,precise structural control of the tethered acceptors enables the synergistic optimization of device efficiency and stability.The main research achievements can be summarized as follows:1.We designed and synthesized a novel series of tethered dimer based on Y6,systematically investigating how flexible linkers of varying lengths modulate the aggregation behavior,relaxation dynamics,and photovoltaic performance of these dimers.Notably,the DY2 dimer incorporating an octyl linker achieved a remarkable open-circuit voltage(V_OC)of 0.87 V and power conversion efficiency（PCE）of 17.85%in optimized devices,outperforming the reference Y6-based devices(V_OC=0.84 V,PCE=16.93%).More importantly,these tethered dimers exhibited significantly elevated glass transition temperatures,effectively suppressing thermodynamic relaxation in the bulk heterojunction blends.Devices incorporating the dimer acceptors retained over 80%of their initial PCE after 700 hours of continuous illumination,demonstrating substantially reduced burn-in losses.This innovative strategy of designing oligomeric acceptors provides a promising pathway for developing organic photovoltaics that simultaneously achieve high efficiency and exceptional operational stability.2.In this chapter,we address the issue of excessive phase separation caused by insufficient miscibility between the conjugated-side-chain-modified tethered acceptor DY-P2EH and polymer donors by proposing a thermodynamically regulated ternary blending strategy.Specifically,we introduced BTP-eC9—a small-molecule acceptor with excellent miscibility with polymer donors—as the third component.By capitalizing on the significant thermodynamic differences between DY-P2EH and BTP-eC9,we successfully constructed a hierarchical phase-separation structure.Our investigations revealed that:（1）The highly miscible BTP-eC9 acceptor spontaneously forms a three-dimensional continuous interpenetrating network within the system,significantly enhancing exciton dissociation efficiency;and（2）The poorly miscible DY-P2EH dimer serves as an"anchoring point"that effectively suppresses the aggregation and migration of small-molecule acceptors.This synergistic mechanism enables the ternary system to achieve outstanding photovoltaic performance（fill factor of 80.61%,power conversion efficiency of 19.09%）while demonstrating exceptional thermal stability（device efficiency degradation rate below 15%after 1100 hours of accelerated aging at 85℃）.3.This chapter presents a novel design strategy for hetero-tethered acceptor molecules,where the star acceptor molecules Y6 and L8BO are covalently connected through flexible linkers to construct a new oligomeric acceptor DY-L.Through combined experimental and theoretical investigations,we systematically studied the influence mechanisms of this hetero-tethered structure on the thermodynamic properties,kinetic behaviors,and device performance.Our research reveals that this intramolecular hetero-tethered strategy achieves precise mixing of Y6 and L8BO acceptor units at the molecular level,demonstrating several remarkable advantages compared to conventional physically blended systems:（1）optimized optoelectronic response characteristics through intramolecular charge transfer effects;（2）regulated intermolecularπ-πstacking behavior,leading to more ordered molecular packing;and（3）significantly altered solution pre-aggregation states,providing a new pathway for active layer morphology control.Remarkably,devices based on DY-L simultaneously exhibit outstanding stability and achieve a record-high power conversion efficiency of 20.54%,representing the highest reported value for oligomer-based binary organic solar cells to date.更多还原