权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Towards next-generation multi-junction solar absorbers - new THz probes of charge dynamics in quantum dots

迈向下一代多结太阳能吸收器——量子点电荷动力学的新型太赫兹探针

基本信息

批准号：
ST/K001981/1
负责人：
Darren Graham
金额：
$ 6.35万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FK001981%2F1
关键词：
Towards next generation multi junction

项目摘要

Solar power is one of the most promising alternatives to using oil, gas and coal to generate the energy we need. The sunlight that reaches the earth from the Sun is enough to supply all our energy needs 10,000 times over. However, today's solar cells are not yet economic; it is still cheaper to produce power by burning fossil fuels and this is preventing their widespread use.How can we make solar cells economically competitive with fossil fuels? There are two ways: make them more cheaply or make them more efficient (or preferably both!) Most of the solar cells we use today are made from silicon and are up to around 20% efficient but expensive to make. Some newer, different types of cell are beginning to become available which are cheaper to make but are only 10% efficient at most. We need to develop solar cells that are both cheap and efficient enough to compete with fossil fuels.One of the most promising ways to do this is by using 'quantum dots' (QDs) - tiny clusters of a few hundred semiconductor atoms that absorb the sunlight and turn it into electricity. They are cheap and easy to make. We can change the colour of sunlight that is absorbed simply by changing the size of the QD. This means we can easily make a higher-efficiency 'multijunction' cell that absorbs more of the sunlight by using dots of several different sizes.This is not the only way in which QDs can lead to higher efficiency. In today's solar cells, about half of the energy from the Sun is wasted as heat when the sunlight is absorbed by the cell. In QDs, however, something else can happen - the energy that would become waste heat in a normal cell can be used instead to produce extra electricity. This is known as 'multiple exciton generation' or 'MEG'. Solar cells based on MEG in QDs could be up to 50% more efficient than today's technology.This is an exciting prospect but we still need to understand this process better. We need to find out what happens in the QD straight after sunlight is absorbed. MEG occurs extremely fast, and is hard to study, so it is difficult to prove whether MEG is happening in a QD or not. To tackle this, we have developed ultrafast laser experiments that give us a snapshot of the current as it is created. We use a very short laser pulse to replicate the sunlight, creating the current. Then we measure what has happened in the sample using a pulse of terahertz radiation (very low energy infrared). This is absorbed very strongly by the current carriers. If we vary the time between the 'pump' pulse and the 'probe' pulse, we can measure what happens to the current very quickly (in around 1/10,000,000,000th of a second). This gives us a measure of the extra electricity created by MEG.We can do this with semiconductor samples with a very large number of atoms, but the conventional terahertz radiation source we use is not powerful enough to study QD samples, which are very dilute. Much higher power compact terahertz sources are being developed in ASTeC at STFC Daresbury Laboratory. The purpose of this application is to use this STFC technology in our measurements to allow us to measure the current created by sunlight in QDs (and MEG), on very fast timescales. We will install and test a number of STFC terahertz sources in our experiments.Measurements like this are very important to the manufacturers of QDs. At the University of Manchester, we have been collaborating for some years with Nanoco Technologies Ltd, the UK's leading manufacturer of QDs. They are interested in the ways in which their dots might be used in future solar cells. In their in-house research they are developing solar cell prototypes that use QDs. In this project we will demonstrate the value of STFC-developed portable high power terahertz sources for QD measurements to Nanoco and the solar industry. At the end of this feasibility study, we hope to develop the technology in partnership with Nanoco and STFC.

太阳能发电是使用石油、天然气和煤炭生产我们所需能源的最有前途的替代方案之一。从太阳到达地球的阳光足以供应我们所需的一万倍以上的能源。然而，今天的太阳能电池还不经济；燃烧化石燃料发电更便宜，这阻碍了它们的广泛使用。我们如何才能使太阳能电池在经济上与化石燃料竞争？有两种方法：让它们更便宜或更有效率(或者最好两者兼而有之！)我们今天使用的大多数太阳能电池都是由硅制成的，效率高达20%左右，但制造成本很高。一些新的、不同类型的电池开始出现，制造成本更低，但最多只有10%的效率。我们需要开发既便宜又高效的太阳能电池，以与化石燃料竞争。最有希望的方法之一是使用量子点(QD)--由数百个半导体原子组成的微小团簇，可以吸收阳光并将其转化为电能。它们既便宜又容易制造。我们可以通过改变量子点的大小来改变被吸收的太阳光的颜色。这意味着我们可以很容易地通过使用几个不同大小的点来制造效率更高的“多结”电池，从而吸收更多的阳光。这并不是量子点能够带来更高效率的唯一方式。在今天的太阳能电池中，当阳光被电池吸收时，大约一半来自太阳的能量被浪费为热。然而，在量子点中，可能会发生其他事情--在正常电池中变成废热的能量可以被用来产生额外的电力。这就是众所周知的“多重激子产生”或“脑磁图”。基于量子点中MEG的太阳能电池的效率可能比今天的技术高出50%。这是一个令人兴奋的前景，但我们仍然需要更好地了解这一过程。我们需要找出太阳光被吸收后QD中直接发生了什么。脑磁图发生得非常快，而且很难研究，所以很难证明脑磁图是否发生在量子点中。为了解决这个问题，我们开发了超快激光实验，让我们在电流产生时得到它的快照。我们使用非常短的激光脉冲来复制太阳光，从而产生电流。然后，我们使用太赫兹辐射(非常低能量的红外线)脉冲来测量样品中发生的事情。这一点被目前的运营商吸收得非常强烈。如果我们改变“泵浦”脉冲和“探测”脉冲之间的时间，我们可以非常迅速地测量电流的变化(大约在十万分之一秒内)。这为我们提供了一种测量MEG产生的额外电能的方法。我们可以对原子数量非常多的半导体样品做到这一点，但我们使用的传统太赫兹辐射源的功率不足以研究非常稀薄的量子点样品。STFC达累斯伯里实验室的ASTEC正在开发功率更高的紧凑型太赫兹源。这个应用程序的目的是在我们的测量中使用这种STFC技术，使我们能够在非常快的时间尺度上测量太阳光在量子点(和Meg)中产生的电流。我们将在实验中安装和测试一些STFC太赫兹源。这样的测量对于量子点制造商来说非常重要。在曼彻斯特大学，我们多年来一直与英国领先的量子点制造商Nanoco Technologies Ltd合作。他们感兴趣的是他们的圆点可能在未来的太阳能电池中的应用方式。在他们的内部研究中，他们正在开发使用量子点的太阳能电池原型。在这个项目中，我们将向Nanoco和太阳能行业展示STFC开发的便携式高功率太赫兹源用于量子点测量的价值。在这项可行性研究结束时，我们希望与Nanoco和STFC合作开发这项技术。