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，以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通过吸收特定波长的光，而是通过将一个波长的光转换为另一个波长而不损失任何能量。太阳能电池提供了一个有用的例子：传统的硅太阳能电池在收集红光能量方面比收集蓝光能量更有效。因此，如果我们在太阳能电池上涂上一层薄膜，在不损失任何能量的情况下，将每个蓝光子转化为两个红光子，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来产生电子-空穴对，然后将其一分为二。正常情况下，这两个电子-空穴对会湮灭，能量会损失，但如果我们能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，在那里它们将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将这个想法转化为我们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，并在它们上覆盖一层非常薄的有机半导体，这样两种材料就可以分子接触。然后我们必须将这些微小的颗粒分散在一层透明的塑料薄膜中，我们可以用它来覆盖太阳能电池-整个过程必须被设计成不会增加太多制造太阳能电池的成本或复杂性。这种太阳能电池涂层只是现在从实验室获得具有新颖和有趣光学特性的最新材料并将其转化为有用产品的潜力的一个例子。另一个例子是只有几个原子厚度的薄片半导体。它们可以非常有效地吸收光线(例如从发光二极管)，并将其重新发射为单一、更纯的颜色。这将帮助我们制造更好的光通信设备和显示设备。但再一次，我们需要学习如何将这些微小的超薄薄膜封装并嵌入到塑料薄膜中，而不是将它们堆叠在一起。解决这些制造问题的关键是了解使这些微小颗粒和薄膜粘合在一起的因素，以及什么处理方法可以使它们分开--通常这将涉及将特殊分子粘在它们的表面。在最终产品中，这些颗粒和片材将分散在塑料片中，我们需要了解，随着塑料薄膜干燥或凝固变硬，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降低我们正在寻找的光学效果的有效性。我们将研究我们用技术制作的薄膜，这些技术允许我们看到粒子周围的各个分子层，以及粒子分散得有多好。通过这种方式，我们将了解制造这类薄膜的规则。到项目结束时，我们的目标是能够与太阳能电池制造商合作，在现实世界中测试我们的想法，并达到产品可以商业化的地步。如果我们成功了，我们将展示我们可以从了解这些新型材料中这些光学和电子效应的基础科学出发，制造出有益的产品，这些产品将造福英国工业，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.