High Performance and Stable Perovskite Solar Cells Based on Vertically Aligned Carbon Nanotube Arrays

探索清洁和可持续的能源资源，以满足日益增长的全球能源需求，成为本世纪最大的挑战之一。这是由于化石燃料在未来50年内将耗尽，以及公众对与化石燃料消耗有关的环境和气候变化的关注。太阳能是最重要的可再生能源之一，因为它的广泛可用性和低环境影响。光伏（PV）太阳能电池可以直接将光子转化为电能，是收集太阳能的理想解决方案。最近的一项预测预测，从现在到2030年，太阳能光伏发电将占全球新增发电装机容量的近三分之一。虽然晶体硅太阳能电池由于组件效率高、技术成熟，仍然主导着光伏市场，但与传统能源相比，其成本竞争力仍然较弱，这就要求开发性能最高、成本最低的新型光伏技术。钙钛矿太阳能电池（PSCs）是一种基于地球资源丰富的材料和廉价沉积技术的新型薄膜太阳能电池。在短短几年的研究工作中，器件性能在功率转换效率（PCE）方面的意外提升从最初的3.8%飙升至认证的22.7%，这在光伏技术的历史上是前所未有的。尽管PSCs在未来几年很有希望占据相当大的光伏市场份额，但它们的商业化仍然受到环境条件下相对较差的材料稳定性的阻碍。此外，太阳能发电的成本不仅取决于光伏组件本身，还取决于框架、逆变器、安装和土地等固定成本。由于固定成本的下降速度不如光伏组件的成本下降速度快，因此持续降低太阳能发电成本的关键途径是在不明显增加光伏组件成本的情况下，提高光伏组件的绝对PCE。在本提案中，我们的目标是通过进一步将最先进的psc的PCE推向其理论极限，同时提高其长期稳定性，为psc大规模部署的这些挑战提供解决方案。我们的方法很大程度上依赖于新材料的结合和器件结构的创新。特别是，我们将采用碳纳米管（CNT）阵列和富勒烯作为电荷收集层，形成一种称为“垂直异质结”的新器件结构。这种“全碳”基PSCs有望表现出比最先进的设备更好的PCE和稳定性。这是因为碳纳米管阵列和富勒烯都是良好的电荷载流子导体，垂直排列的碳纳米管阵列将进一步提高电荷收集效率，因为电荷直接传输到导电衬底，钙钛矿和碳纳米管之间的接触面积更大。本项目的另一个重要创新是碳纳米材料同时作为保护钙钛矿不受潮和受热的封装材料，从而在不增加生产成本的情况下提高了器件的长期稳定性。这项研究将为新型界面材料和器件结构的发展提供新的见解，以实现更高效和稳定的psc，为其未来的商业化提供帮助。虽然该提案主要响应了PSC社区对器件效率和稳定性的详细调查的呼吁，但它自然支持了基于溶液加工薄膜pv的国内研究，从而有助于维持英国美国在先进太阳能电池概念和技术发展方面的领先地位。

Exploring clean and sustainable energy resources to meet the ever-increasing global energy demand becomes one of the biggest challenges in this century. This is due to the depletion of fossil fuels within the next 50 years and public concern on the environmental and climate change related to the consumption of fossil fuels. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Photovoltaic (PV) solar cells that can directly convert photons into electricity present an ideal solution to harvest solar energy. A recent forecast predicts that solar PVs will contribute nearly a third of newly installed electricity generation capacity worldwide between now and 2030. Although crystalline silicon solar cells still dominate the PV market due to high module efficiency and mature techniques, they are still less competitive in cost to the traditional energy resources, which calls for the development of novel PV technologies with the highest performance and the lowest cost. Perovskite solar cells (PSCs) have emerged as a new class of thin film solar cells based on earth-abundant materials and cheap deposition techniques. The unexpected boosting of device performance in terms of power conversion efficiency (PCE) has rocketed up from an initial 3.8% to a certified 22.7% within a few years' research efforts, which is unprecedented in the history of PV technologies. Although PSCs are very promising to take a significant PV market share in the next few years, their commercialization is still hampered by the relatively poor material stability under ambient conditions. Moreover, the cost of solar power is determined not only by the PV modules themselves but also by the fixed costs of frames, inverters, installation and land, etc. Because the fixed costs are not reduced as fast as the cost of PV modules, the key route to continuously reduce the cost of solar powers is to enhance the absolute PCE of the PV modules, without overtly increasing their cost. In this proposal, we aim to provide a solution to these challenges of large-scale deployment of PSCs, by further pushing the PCE of state-of-the-art PSCs toward their theoretical limit, and simultaneously improving their long-term stability. Our methodologies largely rely on the combination of new materials and innovation of device structure. In particular, we will employ carbon nanotube (CNT) arrays and fullerenes as the charge collection layers in a new device structure termed as "vertical heterojunction". This "full carbon" based PSCs are expected to exhibit improved PCE and stability beyond the-state-of-the-art devices. This is because both CNT arrays and fullerenes are good charge carrier conductors, and vertically aligned CNT arrays will further enhance the charge collection efficiency due to the direct charge transport pathways toward the conductive substrates and much larger contact areas between perovskite and CNTs. Another important innovation of this project is that the carbon nanomaterials work simultaneously as the encapsulating materials that protect perovskite from moisture and heat, so as to improve the device long-term stability without increasing production cost. This study will provide new insights into the development of novel interfacial materials and device structures towards more efficient and stable PSCs for their future commercialisation. Whilst this proposal primarily responds to calls within the PSC community for detailed investigations on device efficiency and stability, it naturally supports the domestic research based on solution-processed thin film PVs in general, thereby helping to maintain the U.K.'s leading position in advanced solar cell concepts and technology development.