Optimising polymer photovoltaic devices through control of phase-separation

原则上，光伏器件可以以可持续的方式满足我们所有的能源需求，但目前传统光伏器件的资本成本太高，没有竞争力，而且它们的生产量太小，无法严重削弱我们的发电需求。它们相对较高的制造成本和制造工艺的规模化难度是它们的能量密集型制造工艺的固有特征。相比之下，基于有机半导体的非传统PV可以使用大容量卷对卷印刷技术从溶液中加工，从而提供了以非常低的成本在柔性基板上制造大面积器件的可能性。不幸的是，目前，有机PV器件的特征在于极低的外部功率效率（< 6%）。缩小有机和无机PV器件之间的效率差距是一个重大挑战，需要对目前限制有机PV效率的工艺进行全面的微观理解。目前最有前途的有机PV器件是基于掺杂有富勒烯衍生物的共轭聚合物的溶液浇铸共混物。然而，相对知之甚少的是，关于这种系统的自组装纳米级形态对它们的操作效率的作用。在这个建议中，我们试图发展一个全面的机械理解的自组装过程中，纳米结构出现在这样的光伏适用材料。特别是，我们建议使用X射线散射研究在薄膜铸造过程中纳米级相分离的演变。我们还将利用一系列互补的显微镜技术，从环境扫描电子显微镜，时间分辨近场显微镜。这些技术的结合将使我们能够开发一个完整的图片膜结构从分子到微观的长度尺度。我们提出的项目汇集了一些英国领先的聚合物科学家和技术专家，我们的目标是大大提高对限制有机光伏器件性能的工艺的理解。

In principle, photovoltaic devices could meet all our energy requirements in a sustainable way, but at the moment the capital expense of conventional photovoltaics is too great to be competitive, and the volume in which they can be produced is much too small to make a serious dent in our electricity generating needs. Their relatively high manufacturing cost and the difficulty of scaling the manufacturing process is an intrinsic feature of their energy-intensive fabrication process. In contrast, non-conventional PVs based on organic semiconductors can be processed from solution using high-volume roll-to-roll printing technologies, offering the possibility of large area devices being fabricated on flexible substrates at very low cost. Unfortunately at present, organic PV devices are characterized by prohibitively low external power efficiencies (< 6%). Closing the gap in efficiency between organic and inorganic PV devices is a significant challenge / one which will require a full microscopic understanding of the processes that currently limit organic PV efficiency. The most promising organic PV devices are currently based on solution-cast blends of conjugated polymers doped with fullerene derivatives. Relatively little is however known regarding the role of the self-assembled nanoscale morphology of such systems on their operational efficiency. In this proposal, we seek to develop a comprehensive mechanistic understanding of the self-assembly processes by which nanoscale structure arises within such PV applicable materials. In particular we propose to study the evolution of nanoscale phase-separation during film casting using X-ray scattering. We will also utilize a range of complementary microscopy techniques ranging from environmental scanning electron microscopy, to time-resolved near field microscopy. The combination of such techniques will permit us to develop a complete picture of film structure from molecular to microscopic length-scales. Our proposed project draws together some of the UK's leading polymer scientists and technologists, with our goal being to significantly advance the understanding of the processes that limit organic PV device performance.