Intermolecular Charge Transport: A Novel Design Paradigm

预计可再生能源将在实现我们的目标方面发挥重要作用，即在2050.1年前结束英国对全球变暖的贡献。钙钛矿型太阳能电池等新兴薄膜技术正在将光伏的范围扩大到传统硅基太阳能电池有效能力之外的应用。这些器件能够在弱光条件下工作，并且可以很容易地作为廉价的轻便灵活的器件进行印刷，使它们适合于集成到室内和便携式系统中。2PSC的高效率为25.2%，在硅基串联电池中的效率为28%。3它们使用丰富的、低成本的起始材料，并且比传统的硅太阳能电池的能量密集度更低。4然而，关键的挑战仍然是在控制这些器件的整体性能和成本方面发挥主要作用的空穴传输材料(HTM)。4光照射到钙钛矿吸收体会将其电子激发到更高的能级，留下一个带正电的“黑洞”。然后，HTM将这些孔从吸收体向电极方向穿梭，允许电流流过该设备。其中一个问题是电荷重组，这限制了效率。此外，最新的高温超导材料，如Spiro-OMeTAD，价格昂贵，合成困难。4新型高温超导材料的开发成本仅为传统材料的一小部分，使用简单的化学方法。4，5，6它们的合成可以在环境条件下进行，不需要金属催化，并且微不足道的分离技术提供了高产率和高纯度的产品。通过组合不同的核心和侧基，可以创建HTM库，调整结构以优化其性能。然而，这些新材料的性能仍然没有超过最先进的HTM。本项目旨在研究HTM对分子间电荷传输的影响。通过理论和实验相结合的方法，我们希望了解通过凝聚化学合成的新型材料在骨架中具有破坏共轭的改善的电荷传输性能。4将开展理论研究来研究已知的HTMS的性质，包括导电性和电荷载流子迁移率。基于我们的发现，我们的目标是设计和合成改进的材料，这些材料将作为纯空穴器件和PSC内部进行测试。将对已知的HTMS进行计算研究，研究中性和带电物种以及从基态到激发态的跃迁。这些结果将被用来深入了解影响性能的性质，如载流子迁移率、堆积和溶解度。我们的研究结果将指导设计具有更好的电荷传输性能的新型高温超导材料。分子将在我们的分子范围内扩展，使用缩合化学合成，最初在骨架上破坏共轭。与性能相关的分子的光电和物理性质将在仅限空穴的设备和PSCS中进行测试。分子性质将通过紫外-可见吸收光谱和循环伏安实验计算出来。将测量HTMS的电导率和载流子迁移率。最后，对HTM薄膜的热转变、稳定性和形貌进行了分析。具有合适性能的高温超导材料将被用于制备PSC，并将对这些器件的结构和光伏特性进行研究。使用迭代方法，我们的结果将被用于优化设计过程，并达到更好的HTMS性能。

Renewable energy is expected to play a major role in reaching our target to end the UK's contribution to global warming by the year 2050.1 Emerging thin-film technologies, such as perovskite solar cells (PSC), are widening the scope of photovoltaics (PVs) to applications beyond the effective capabilities of conventional silicon based PVs. These devices are able to operate under low light conditions and can be printed easily as cheap lightweight-flexible devices, making them suitable for integration within indoor and portable systems.2PSCs with high efficiencies of 25.2%, and 28% within silicon-based tandem cells, have been already demonstrated.3 They make use of abundant, low-cost starting materials and are less energy intensive to produce than conventional silicon solar cells.4 However, a key challenge remains the 'hole' transport material (HTM) which plays a major role in controlling the overall performance and cost of these devices.4 Light hitting the perovskite absorber causes excites its electrons to a higher energy level, leaving behind a positively charged 'hole'. The HTM then shuttles these holes away from the absorber and toward the electrode allowing a current to flow through the device. One problem is charge recombination, which limits efficiency. In addition, state-of-the-art HTMs, such as spiro-OMeTAD, are expensive and difficult to synthesise.4Novel HTMs, have been developed at a fraction of the cost of conventional materials, employing simple chemistry.4,5,6 Their synthesis can be carried out under ambient conditions,without the need for metal catalysis, and trivial isolation techniques furnish products in high yields and purities. By combining different core and side groups, HTM libraries can be created, tuning structures to optimise their performance. However, these novel materials still do not outperform state-of-the-art HTMs.This project aims to investigate intermolecular charge transport affected by the HTM. By combining theoretical and experimental approaches, we are looking to understand the improved charge transport properties of novel materials, synthesised using condensation chemistry, with disrupted conjugation in the backbone.4 Theoretical studies will be carried out to investigate the properties of known HTMs, including conductivity and charge carrier mobility. Based on our findings we aim to design and synthesise improved materials which will be tested, both as 'hole'-only devices and within PSCs.Computational studies of known HTMs will be conducted, studying the neutral and charged species as well as transitions from the ground state to the excited state. These results will be used to gain an insight into properties, such as charge carrier mobility, packing and solubility, that effect performance. Our findings will guide the design of novel HTMs with improved charge transport properties. Molecules will be synthesised that expand on our range of molecules, synthesised using condensation chemistry, initially with disrupted conjugation in the backbone.Performance-related optoelectronic and physical properties of the molecules, will be tested both in 'hole'-only devises and within PSCs. Molecular properties will be calculated from UV-visible absorption spectra and cyclic voltammetry experiments. The conductivity and charge-carrier mobilities of HTMs will be measured. Finally, thermal transitions, stability and profile of HTM films will be analysed. HTMs with the appropriate properties will be used to fabricate PSCs and the structure and PV characteristics of these devices will be studied. Using an iterative approach, our results will be used to optimise the design process and arrive at better performing HTMs.