EAGER: Novel Interfaces for Nanostructured Solar Cells

染料敏化太阳能电池是一种很有前途的低成本太阳能转换技术，在这种技术中，吸附在半导体上的染料分子吸收光，向半导体注入一个光注入的电子(成为氧化物)，然后被溶解的碘还原(再生)，得到中性染料和三碘化合物。电子从半导体中收集，通过外部电路，然后返回到对电极，在那里它将三碘化合物还原为碘化物，完成电路。通过碘化物还原氧化染料需要很大的过电位(至少0.5V)，这在DSSC中构成了显著的能量损失。可以以更小的过电位还原氧化染料的替代氧化还原对往往会以高速率从半导体中移除电子，用一个损失过程取代另一个损失过程。克服后一个问题(复合)需要提高电子在半导体中的传输速度，以便电子可以在复合之前被提取出来。这一探索性项目将产生初步数据，以展示新的复合半导体纳米结构解决这一问题的潜力。智能价值这项工作的设计范式是将两种半导体材料切割：一种是染料分子在其上吸附和注入电子的有源层，另一层是从有源层提取电荷并将其快速传输到导电衬底进行收集的传输层。有源层必须具有较高的表面积，以允许每个几何区域有较大的染料负载量，以便强吸收入射太阳光。这项工作将产生这一范式的两个实例。一种是由包裹在氧化锌纳米棒上的二氧化钛纳米颗粒组成；纳米棒提供快速的传输，而纳米颗粒大大增加了总表面积。另一种是在掺氟氧化锡(FTO)气凝胶上形成一层适形的二氧化钛。气凝胶本质上是高比表面积结构，允许对活性层进行保形涂层。该项目的重点是关于阻挡层以阻止复合的初步数据，FTO气凝胶样品中氟掺杂水平的分析，以及使用新型复合半导体薄膜制作的太阳能电池器件的光电测量。广泛影响这项研究将显著推进低成本太阳能转换技术，面对大量人口能源使用量的急剧增加以及迫在眉睫的气候变化和其他化石燃料燃烧对环境的影响，这一技术的需求日益迫切。该项目将向相关研究生提供教育和培训，包括撰写研究文章和前往国内和国际会议传播成果。PI积极地让K-12年级的学生和教师使用DSC作为与能源、环境、化学和工程相关的主题的教学工具。

The dye-sensitized solar cell (DSSC) is a promising technology for low-cost solar energy conversion in which a dye molecule adsorbed on a semiconductor absorbs light, injects a photoinjected electron into the semiconductor (becoming oxidized), and is reduced (regenerated) by dissolved iodide, giving the neutral dye and triiodide. The electron is collected from the semiconductor, travels through an external circuit, and is returned to a counterelectrode where it reduces triiodide to iodide, completing the circuit. The reduction of oxidized dyes by iodide requires a large overpotential (at least 0.5 V), constituting a significant energy loss in the DSSC. Alternative redox couples that can reduce oxidized dyes with much smaller overpotentials tend to remove electrons from the semiconductor at high rates, replacing one loss process with another. Surmounting this latter problem (recombination) requires increasing the speed of electron transport in the semiconductor, in order that the electron may be extracted before it is lost to recombination. This exploratory project will generate preliminary data to demonstrate the potential for new composite semiconductor nanostructures to solve this problem.Intellectual MeritThe design paradigm that governs this work is the paring of two semiconducting materials:an active layer on which dye molecules adsorb and inject electrons, and a transport layer that extracts charges from the active layer and rapidly transports them to the conducting substrate for collection. The active layer must have a high surface area to allow a large dye loading per geometric area for strong absorption of incident sunlight. Two instances of this paradigm will be produced in this work. One consists of titania nanoparticles coated over zinc oxide nanorods; the nanorods provide fast transport while the nanoparticles greatly increase the total surface area. The other is a conformal layer of titania over a fluorine-doped tin oxide (FTO) aerogel. The aerogel is inherently a high-surface area structure, allowing a conformal coating of the active layer. This project focuses on preliminary data regarding blocking layers to retard recombination, analysis of fluorine dopant levels in FTO aerogel samples, and optoelectronic measurements of solar cell devices made with the novel composite semiconductor films.Broader ImpactsThis research will significantly advance the technology of low-cost solar energy conversion, for which there is an increasingly urgent need in the face of sharply increasing energy usage among a large population together with impending climate change and other environmental impacts from fossil fuel combustion. The project will provide education and training to involved graduate students including the writing of research articles and travel to domestic and international conferences for dissemination of the results. The PI actively engages K-12 students and teachers using the DSSC as a teaching tool for topics related to energy, the environment, chemistry and engineering.