Equilibrium and non-equilibrium behaviour in polymer/small-molecule mixtures for organic photovoltaic (OPV) applications

有机光伏 (OPV) 应用中聚合物/小分子混合物的平衡和非平衡行为

• 批准号: 2889023
• 金额: --
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2889023
• 关键词: Equilibrium; non; equilibrium; behaviour; polymer

Project: This project aims to understand fundamental aspects of the behaviour of organic photovoltaic (OPV) materials. The studentship will build on recent investigations into the mixing of polymer/small-molecule bilayers in a thin-film geometry. The objective of the project is to assess the degree to which model, amorphous, polymer/small-molecule blends equilibrate under thermal annealing. Whether or not thermodynamic equilibrium is reached will be assessed via two sets of measurements; the composition/phase volume of the two layers (in general, the layers can be pure or mixed at equilibrium) and the width of the interface between them. This will be investigated by the development and implementation of in-situ neutron reflectometry techniques to allow rapid measurements, and extensive annealing (including thermal cycling) of these materials at elevated temperatures. These neutron studies will be complimented by a range of laboratory investigations, include x-ray scattering (both wide and small angle to assess any crystal formation and larger scale structure, respectively), atomic force microscopy (to assess any in-plane surface structure), and various spectroscopic techniques (to ensure material integrity).Equilibrium will be assessed by; i) investigating the reversibility of composition, phase-volume and interfacial width changes, as a function of temperature; ii) investigating convergence (or otherwise) to an equilibrium state from different starting positions; iii) investigating changes to composition and interfacial width as a function of polymer molecular weight in comparison to existing theoretical predictions. Investigations to-date, in a model polymer/fullerene system, have uncovered situations in which equilibration occurs, and situations in which non-equilibrium (hysteresis) behaviour occurs. Two key aims of the studentship are i) to investigate whether novel non-fullerene-acceptor (NFA)/polymer systems evolve towards equilibrium and can be understood within a framework of existing theory, and ii) to further characterise the nature of the hysteresis in thermally annealed bilayers and try to understand why this occurs.Context: The outcomes of the project are potentially important in two aspects. Firstly, the equilibrium compositions of mixed domains have recently been linked to device efficiency. Correct determination of whether or not a system has properly equilibrated will have important implications for workers who wish to extract equilibrium parameters from intermixing experiments. Secondly, the proximity of optimised (but potentially non-equilibrated) domains within devices to equilibrium is of crucial importance with regard to device stability, as compositions may evolve towards equilibrium during operation (under thermal cycling).

项目：该项目旨在了解有机光伏（OPV）材料行为的基本方面。该学生将建立在最近对聚合物/小分子双分子层在薄膜几何结构中的混合的研究基础上。该项目的目标是评估模型，非晶，聚合物/小分子混合在热退火下的平衡程度。是否达到热力学平衡将通过两组测量来评估；两层的组成/相体积（一般来说，两层在平衡状态下可以是纯的或混合的）和它们之间的界面宽度。这将通过原位中子反射技术的发展和实施来研究，以允许快速测量，并在高温下对这些材料进行广泛的退火（包括热循环）。这些中子研究将得到一系列实验室研究的补充，包括x射线散射（分别用于评估任何晶体形成和更大规模结构的宽角度和小角度），原子力显微镜（用于评估任何面内表面结构）和各种光谱技术（以确保材料完整性）。平衡将由；1)研究组分、相体积和界面宽度随温度变化的可逆性；Ii)研究从不同起始位置到平衡状态的收敛性（或其他）；Iii)与现有的理论预测相比，研究聚合物分子量对组成和界面宽度的影响。迄今为止，在模型聚合物/富勒烯体系中，已经发现了发生平衡和发生非平衡（滞后）行为的情况。该研究的两个关键目标是：1)研究新的非富勒烯受体(NFA)/聚合物系统是否向平衡方向发展，是否可以在现有理论的框架内理解；2)进一步表征热退火双层中滞后的性质，并试图理解为什么会发生这种情况。背景：项目的结果在两个方面具有潜在的重要性。首先，混合畴的平衡组成最近与器件效率有关。对于希望从混合实验中提取平衡参数的工作人员来说，正确确定系统是否达到适当的平衡具有重要意义。其次，设备内优化（但潜在的非平衡）区域接近平衡对于设备稳定性至关重要，因为组合物可能在操作期间（在热循环下）向平衡方向发展。