UNS: Rare Earth Oxides for Hybrid Photovoltaics

太阳代表着地球上最丰富的潜在可持续能源。由纳米级氧化钛晶体薄膜制成的太阳能电池可能比目前商用太阳能电池中使用的晶体硅材料便宜得多，但太阳能转换效率较低。该项目的目标是确定在氧化钛层中添加稀土材料如何提高太阳能转换效率。该研究计划将把重点放在氧化钕作为模型稀土材料上。在这项研究中获得的基础科学也可能导致发现新的量子力学过程，以提高太阳能电池的电流生产。作为该项目的一部分，路易斯维尔大学的学生将与瑞士联邦理工学院世界知名的太阳能研究机构合作。染料敏化和钙钛矿太阳能电池含有氧化钛纳米晶体薄膜，作为光激发电子的受体，相对于掺杂晶体硅材料提供了低成本的制造，但太阳能转换效率仍然低于20%。本研究的总体目标是了解如何将稀土氧化物掺入钙钛矿和染料敏化光伏材料的氧化钛层中，以最佳方式实现提高太阳能转换效率。在氧化钛层中掺入稀土氧化物可以通过三种可能的机制潜在地增强超过Shockley-Queisser极限的短路电流密度。首先，稀土和敏化剂之间的光学跃迁耦合为载流子倍增效应提供了机会。其次，稀土中f态电子的自旋矩与敏化剂之间的交换相互作用导致三重态和单重态激子之间的混合，导致光学吸光度增强。稀土氧化物的低电子亲和和高介电常数使得空穴输运效率高。研究计划将利用电子和扫描探针显微镜、空间光电化学测量、扫描能量色散x射线元素图和拉曼化学图，通过光学和电子性质与稀土氧化物掺杂薄膜的组成和形貌的相关性来阐明效率增强机制。这些知识将用于开发、制造和测试使用氧化钕作为模型稀土氧化物材料的稀土氧化物/钙钛矿混合太阳能电池。在最基本的层面上，这些研究可能会导致发现涉及电光和电子自旋相互作用的光电流增强新机制，这可能会应用于其他类型的光伏材料。研究中使用的分析和材料合成方法将适用于本科阶段的纳米技术教学模块。推广和扩大参与活动将通过技术研究员计划和路易斯维尔大学康恩可再生能源研究中心进行协调。

PI: Bruce AlphenaarProposal Number: 1512106The sun represents the most abundant potential source of sustainable energy on earth. Solar cells made from thin films of nanometer sized crystals of titanium oxide are potentially much less expensive that crystalline silicon materials currently used in commercial solar cells, but suffer from low solar energy conversion efficiencies. The goal of this project is to determine how the addition of rare earth materials into the titanium oxide layer can improve solar energy conversion efficiency. The research plan will focus on neodymium oxide as model rare earth material. The fundamental science gained in this research may also lead to the discovery of new quantum mechanical processes for enhancing current production from solar cells. As part of this project, students at the University of Louisville will collaborate with a world-renowned solar energy research facility at the Swiss Federal Institute of Technology.Dye-sensitized and perovskite solar cells containing titanium oxide nanocrystal thin films which act as the acceptor for photoexcited electrons offer low-cost fabrication relative to doped crystalline silicon materials, but solar energy conversion efficiencies are still below 20%. The overall goal of the proposed research is to understand how the incorporation of rare earth oxides into the titanium oxide layer of perovskite and dye-sensitized photovoltaic materials can be optimally realized to increase solar energy conversion efficiency. The incorporation rare earth oxides into the titanium oxide layer can potentially enhance short circuit current densities exceeding the Shockley-Queisser limit by three possible mechanisms. First, the coupling of optical transitions between the rare earth and the sensitizer provides the opportunity for carrier multiplication effects. Second, exchange interactions between the spin moment of the f-state electrons in the rare earth and the sensitizer causes mixing between the triplet and singlet excitons, leading to enhanced optical absorbance. Third, the low electron affinity and high dielectric constant of rare earth oxides enable efficient hole transport. The research plan will elucidate the efficiency enhancement mechanisms through correlation of the optical and electronic properties with the composition and morphology of the rare-earth oxide doped films using electron and scanning probe microscopy, spatial photoelectrochemical measurements, scanning energy dispersive X-ray elemental mapping, and Raman chemical mapping. This knowledge will then be used to develop, fabricate, and test rare-earth oxide / perovskite hybrid solar cells using neodymium oxide as the model rare earth oxide material. At the most fundamental level, these studies could lead to the discovery of new mechanisms for photocurrent enhancement involving electro-optic and electron spin interactions which can potentially be applied to other types of photovoltaic materials. The analytical and materials synthesis methods used in the research will be adapted for use in nanotechnology instructional modules at the undergraduate level. Outreach and broadening participation activities will be coordinated through the Technology Fellows Program and the Conn Center for Renewable Energy Research at the University of Louisville.