Rational design of manufacturing processes for next generation optoelectronically active nanocomposite films and coatings

我们的研究旨在开发塑料薄膜或涂层，改变通过它们的光的颜色和其他特性，而不是像简单的滤色器那样吸收某些波长的光，而是通过将一种波长的光转换为另一种波长而不损失任何能量。太阳能电池提供了一个为什么这将是有用的例子：传统的硅太阳能电池在收集红光能量方面比蓝光更有效。因此，如果我们在太阳能电池上涂上一层薄膜，可以将每一个蓝色光子转换为两个红色光子，在这个过程中不会损失任何能量，原则上我们可以使硅太阳能电池的效率提高30%。我们之前在剑桥的研究已经在原则上展示了如何做到这一点。某些有机半导体会吸收一个蓝色光子，产生一个电子空穴对，然后分裂成两个。正常情况下，这两个电子空穴对会湮灭，能量会损失，但如果我们可以安排有机半导体与无机半导体量子点进行分子接触，那么电子空穴对就可以迁移到量子点，在那里它们会重新结合并发射两个红色光子。我们现在要解决的问题是如何把这个想法变成一个可以大规模生产的实际产品。我们需要能够制造出不会聚集在一起的半导体纳米晶体，并在它们外面涂上一层非常薄的有机半导体，这样两种材料就能分子接触。然后我们必须把这些微小的颗粒分散在一个透明的塑料薄膜中，我们可以用它来覆盖太阳能电池整个过程必须设计得使其不会过多地增加太阳能电池的成本或复杂性。这种太阳能电池的涂层只是一个例子，说明现在有可能从实验室中获得具有新颖有趣的光学特性的最新材料，变成有用的产品。另一个例子是只有几个原子厚的半导体薄片。这些可以非常有效地吸收光（例如来自发光二极管）并将其重新发射为单一，更纯的颜色。这将有助于我们制造更好的光通信设备和显示设备。但我们需要再次学习如何将这些微小的片状物封装并嵌入塑料薄膜中，而不会使它们粘在一起。解决这些制造问题的关键是了解使这些微小颗粒和片状物粘在一起的因素，以及什么样的处理方法可以使它们分开-通常这需要在它们的表面粘上特殊的分子。在最终产品中，这些颗粒和薄片将分散在塑料薄片中，我们需要了解随着塑料薄膜变干或变硬，干燥过程如何影响颗粒，以及干燥薄膜中发生的过程是否会使我们正在寻找的光学效果变得不那么有效。我们将研究我们用技术制作的薄膜，这些技术使我们能够看到颗粒周围的单个分子层，以及颗粒的分散程度。通过这种方式，我们将了解制造这类薄膜的规则。在项目结束时，我们的目标是能够与太阳能电池制造商合作，在真实的世界中测试我们的想法，并达到产品可以商业化的程度。如果我们成功了，我们将证明，我们可以从理解这些新型材料中的光学和电子效应的基础科学出发，制造出有益于英国工业的有用产品，并帮助解决气候变化问题。

Our research aims to develop plastic films or coatings that change the colour and other characteristics of the light that passes through them, not by absorbing certain wavelengths of light, as a simple colour filter would, but by converting light of one wavelength to another without losing any energy. Solar cells offer an example of why this would be useful: conventional silicon solar cells are more efficient at collecting the energy of red light than they are of blue light. So if we coated the solar cell with a film that would convert every blue photon into two red photons, without losing any energy in the process, in principle we could make the silicon solar cells 30% more efficient.Our previous research at Cambridge has shown in principle how this could be done. Certain organic semiconductors will absorb a blue photon to produce an electron-hole pair, which then splits into two. Normally these two electron-hole pairs would annihilate and the energy would be lost, but if we can arrange for the organic semiconductor to be in molecular contact with an inorganic semiconductor quantum dot, then the electron-hole pairs can migrate to the quantum dot, where they will recombine and emit two red photons. The problem we now want to solve is to work out how to turn this idea into a practical product that we can manufacture on a large scale. We need to be able to make semiconductor nanocrystals that won't clump together, and to coat them with a very thin layer of the organic semiconductor so the two materials are in molecular contact. Then we have to disperse these tiny particles in a clear plastic film, which we can use to coat a solar cell - and the whole process has to be designed so that it doesn't increase the cost or complexity of making the solar cell too much.This coating for solar cells is just one example of the potential there now is for taking the latest materials from the laboratory with novel and interesting optical properties and turning them into useful products. Another example is provided by thin sheets of semiconductors only a few atoms thick. These can be very efficient at absorbing light (for example from a light emitting diode) and reemitting it as a single, purer, colour. This will help us make better optical communication devices and display devices. But once again, we need to learn how to encapsulate and embed these tiny, ultrathin sheets into a plastic film without them sticking together in stacks.The key to solving these manufacturing problems is understanding the factors that make these tiny particles and sheets stick together and what treatments could keep them apart - often this will involve sticking special molecules to their surfaces. In the final products, these particles and sheets will be dispersed in a plastic sheet, and we need to understand how, as the plastic film dries or sets hard, the drying process affects the particles, and whether the processes that take place in the drying film makes the optical effects we're looking for less effective. We will be studying the films we make with techniques that allow us to see the individual molecular layers around the particles, as well as how well the particles are dispersed. In this way we'll understand the rules for manufacturing these sorts of films.By the end of the project, we aim to be able to work with solar cell manufacturers to test our idea in the real world and get to the point where a product can be commercialised. If we are successful, we'll have demonstrated that we can go from understanding the fundamental science of these optical and electronic effects in these new kinds of materials to make useful products that will benefit UK industry and help solve problems of climate change.