Photophysical Strategies and Novel NIR Dyes for Optimisation of Luminescent Solar Concentrators

现在人们普遍认为，近几个世纪以来，世界对化石燃料的日益依赖正在导致地球气候发生剧烈变化。可再生能源技术——如太阳能、风能和波浪能——为生产清洁能源提供了一条途径。该项目涉及光伏（PV）技术——将太阳光转化为电能——特别是涉及将发光材料应用于光伏组件。自1999年以来，光伏组件的出货量一直以每年45%的速度稳定增长，然而硅原料供应的短缺预计将在未来几年持续下去，因为太阳能电池的成本占光伏组件最终成本的70%。硅原料用于制造当今近95%的太阳能电池。因此，新技术对于满足对光伏产品的指数级需求至关重要。该项目追求一种替代光伏技术，称为发光太阳能聚光器（LSC）。这项技术的主要优点是降低了成本，因为大面积的硅太阳能电池被廉价的塑料片所取代。这项新技术的诀窍是将荧光染料嵌入塑料片中。这些染料吸收入射到薄膜上的阳光，然后重新发射这种光，这样75%的光被困在塑料薄膜内，并反射到薄膜的边缘，然后看起来非常明亮。通过在薄片周围放置太阳能电池，这种集中的光被转换成电能。因此，LSC技术可以被设想为一个发电窗口。由于光集中在薄片的边缘，因此只需要一小部分太阳能电池来覆盖这一区域，从而节省了大量成本。LSC技术的进一步优势是：-现有的高效硅太阳能电池可以使用，类似于今天商业化生产的太阳能电池，这意味着不需要花费宝贵的研究时间和资金来开发新的太阳能电池。- LSC模块不需要像其他基于透镜和反光镜的太阳能集中系统那样，跟踪太阳在天空中的路径来集中光线。此外，LSC在阴天同样高效，使其成为欧洲大部分地区非常相关的光伏技术，这是传统太阳能集中系统无法实现的。- LSC技术非常适合集成到建筑物中（建筑集成光伏，BIPV），因为i)它能够充当电活动窗口，ii)能够调整LSC模块的颜色以提供吸引人的外观。在该技术实现之前，LSC系统的性能需要得到显著提高，目前LSC的世界纪录转换效率为3.2%。这项研究计划汇集了一个由光伏工程师和化学家组成的跨学科团队。新的染料将被制造，这将使LSC实现两个新的结果。首先，将开发能够吸收600 - 900nm太阳波长的染料，这是目前染料无法有效集中的大部分太阳光谱。其次，控制染料的光发射将允许光被引导到聚光器边缘，而不是在随机的方向上发射，这样就会通过塑料片的表面损失一定比例的光。这将导致所有的发光到达LSC的边缘，使性能提高25%。最初的建模结果表明，如果这两种策略都成功并且可以集成在一起，那么转换效率可以达到11%。

It is now widely accepted that the world's increasing reliance on fossil fuels over recent centuries is causing drastic changes in the Earth's climate. Renewable energy technologies - such as solar, wind and wave energy - offer a pathway for the generation of clean energy. This project concerns photovoltaic (PV) technology - the conversion of sunlight to electricity - and, in particular, involves the application of luminescent materials to PV modules. Shipments of PV modules have been increasing at a steady rate of 45% per annum since 1999, however a shortfall in silicon feedstock supplies - the material used to fabricate nearly 95% of today's solar cells - is expected to continue for the next few years, This is significant as the cost of the solar cells makes up 70% of the final cost of a PV module. New technologies are therefore extremely important to satisfy the exponential demand for PV products, This project pursues an alternative PV technology called the luminescent solar concentrator (LSC). The primary advantage of this technology is reduced cost since large areas of silicon solar cells are replaced with cheap plastic sheets. The trick to the new technology involves fluorescent dyes embedded in the plastic sheet. These dyes absorb sunlight that is incident on the sheet and then re-emit this light such that 75% of the light is trapped within the plastic sheet and is reflected to the edges of the sheet, which then appear very bright. This concentrated light is converted to electricity by then placing solar cells along the perimeter of the sheet. Thus, the LSC technology can be envisaged as being an electricity-generating window . Because the light is concentrated at the edge of the sheet, only a fraction of solar cells are required to cover this area resulting in large cost savings. Further advantages of the LSC technology are: - That existing high-efficiency silicon solar cells can be used, similar to those that are commercially produced today, meaning that valuable research time and funding does not need to go into developing a new solar cell. - The LSC module does not have to track the path of the sun across the sky in order to concentrate the light, as is required with other lens and mirror-based solar concentrating systems. In addition, the LSC is equally efficient on cloudy days making it a very relevant PV technology for the majority of Europe - something that cannot be achieved with traditional solar concentrating systems.- The LSC technology is ideally suited for integration into buildings (building integrated photovoltaics, BIPV),due to i) its ability to act as an electrically active window, ii) being able to adjust the colour of the LSC module to give an appealing appearance. Before the technology can be realised, the performance of the LSC system needs to be significantly improved, with the current LSC world-record conversion efficiency standing at 3.2%. This research proposal brings together an interdisciplinary team comprised of PV engineers and chemists. Novel dyes will be fabricated that will enable the LSC to achieve two new results. Firstly, dyes will be developed that can absorb solar wavelengths of 600 - 900nm, a large part of the solar spectrum that current dyes cannot efficiently concentrate. Secondly, controlling the light emission from dye will allow the light to be directed towards the concentrator edge rather than being emitted in random directions such that a percentage is lost through the faces of the plastic sheet. This would result in all the luminescence reaching the edge of the LSC giving a 25% boost in performance. Initial modelling results indicate that conversion efficiencies of up to 11% could be realisable if both of these strategies are successful and can be integrated together.