Carrier Dynamics in Quantum Dot Solar Cells and Infrared Detectors

量子点太阳能电池和红外探测器中的载流子动力学

• 批准号: 1509712
• 负责人: Mario Dagenais
• 金额: $ 39.44万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1509712&HistoricalAwards=false
• 关键词: Carrier; Dynamics; Quantum; Dot; Solar

Abstract:Abstract Title: "Understanding the enhancement mechanisms of optical energy conversion efficiency in solar cells based on confinement by quantum dots"Nontechnical:Photovoltaic is a technology that permits the conversion of abundant radiative energy from the sun to electrical energy which can ultimately be widely distributed using a smart electrical grid infrastructure. This can be done with a minimum negative impact on the environment. In spite of being a well-established clean source of energy, there is a need for improving the present conversion efficiency of Si solar cells. New materials and new approaches to achieve this goal have emerged. One appealing approach is based on using different materials with different bandgap to enhance the conversion efficiency of present solar cells. Another approach is based on using confined nanostructures, called quantum dots, to convert solar energy with high efficiency. This latter approach has the advantage of being simpler and does not require complex growth processes. This might be a very inexpensive approach to making solar cells. On the other hand, this approach has not yet demonstrated its potential. Different experimental studies are proposed with the goal of understanding the potential and limitations of this approach. The proposed approach involves an effort toward a better understanding of light absorption in these structures in order to design very efficient solar cells based on quantum dots. If successful, this project will have a major impact on clean and efficient energy conversion in this country.Technical:Photovoltaic devices based on p-n junction are the most mature technology for solar-energy harvesting. This proposal seeks to develop new highly efficient GaAs quantum dot solar cells based on the intermediate band concept. These cells have the potential of being as efficient as 3-junction solar cells but at a much lower level of complexity. The concept of intermediate band solar cells has been with us for more than 15 years. Unfortunately, these solar cells have so far demonstrated a limited conversion efficiency of 18 % or less. This is in large part related to the fact that researchers have not been able to demonstrate an intermediate band solar cell with a well-defined intermediate band Fermi energy, detached from the conduction band Fermi energy. Some key measurements on intermediate band solar cells that have not been attempted before are proposed in order to shed light on this topic. In particular, two-photon measurements using two optical sources of different wavelengths are proposed to understand if a 2-photon absorption can be measured and if the process is based on sequential photons absorption or due to simultaneous two-photon absorption. This will answer the question if intermediate band solar cells can be realized with well-defined intermediate band Fermi energy, detached from the conduction band Fermi energy. If substantially higher efficiencies cannot be reached using the concept of intermediate band solar cells, implying that the concept is basically flawed, this needs to be investigated and a final answer has to be provided with a clear explanation. Additionally, since the physics of these solar cells is similar to the physics describing photon absorption in IR-detectors, this new understanding will also lead to a better understanding of the operation of quantum dot infrared photodetectors (QDIPs). Two quantum dot solar cells will be studied with different bandgaps to optimize the predicted conversion efficiency of intermediate band solar cells.

摘要：标题：《理解基于量子点限制的太阳能电池光能转换效率的增强机制》非技术性：光伏是一种技术，它允许将来自太阳的丰富辐射能量转换成电能，最终可以使用智能电网基础设施广泛分布。这可以在对环境的负面影响最小的情况下完成。尽管硅太阳能电池是一种公认的清洁能源，但仍有必要提高目前的转换效率。实现这一目标的新材料和新方法应运而生。一种吸引人的方法是使用不同材料和不同的带隙来提高现有太阳能电池的转换效率。另一种方法是基于使用被称为量子点的受限纳米结构来高效地转换太阳能。后一种方法的优点是更简单，不需要复杂的生长过程。这可能是制造太阳能电池的一种非常便宜的方法。另一方面，这种方法尚未显示出其潜力。为了了解这种方法的潜力和局限性，提出了不同的实验研究。建议的方法包括努力更好地了解这些结构中的光吸收，以便设计基于量子点的非常高效的太阳能电池。如果该项目成功，将对我国清洁高效的能源转换产生重大影响。技术：基于p-n结的光伏器件是目前最成熟的太阳能集热技术。这一建议旨在开发基于中间带概念的新型高效GaAs量子点太阳能电池。这些电池有可能与三结太阳能电池一样高效，但复杂性要低得多。中间波段太阳能电池的概念已经伴随我们超过15年了。不幸的是，到目前为止，这些太阳能电池的转换效率有限，只有18%或更低。这在很大程度上与这样一个事实有关，即研究人员尚未能够证明具有明确定义的中间带费米能量的中间带太阳能电池，该电池与传导带费米能量分离。为了阐明这一主题，提出了一些以前从未尝试过的关于中间波段太阳能电池的关键措施。特别是，建议使用两个不同波长的光源进行双光子测量，以了解是否可以测量双光子吸收，以及该过程是基于顺序的光子吸收还是由于同时的双光子吸收。这将回答这样一个问题，即是否可以用定义良好的中间带费米能量来实现中间带太阳电池，将中间带费米能量从导带费米能量中分离出来。如果使用中间波段太阳能电池的概念不能实现显著更高的效率，意味着这一概念基本上是有缺陷的，就需要对此进行调查，并必须提供一个明确的解释来最终回答这个问题。此外，由于这些太阳能电池的物理学类似于描述红外探测器中光子吸收的物理学，这种新的理解也将有助于更好地理解量子点红外光电探测器(QDIP)的工作原理。为了优化中间带太阳电池的预测转换效率，将对两个不同带隙的量子点太阳电池进行研究。