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Role of Small Angle Grain Boundaries in CdTe Solar Cell Performance

小角度晶界在 CdTe 太阳能电池性能中的作用

基本信息

批准号：
1711534
负责人：
Nikolas Podraza
金额：
$ 35.25万
依托单位：
University of Toledo
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1711534&HistoricalAwards=false
关键词：
Role Small Angle Grain Boundaries

项目摘要

Abstract Title: Role of Grain Boundaries in CdTe Solar Cell Performance Non-Technical Description: Solar power is of interest to address the growing global energy demand as it is renewable, low environmental impact, and potentially low cost. Within thin film solar technology, power is generated from incident light absorbed in a microns-thin semiconducting active layer of the device, among a stack of other thin film layers on a supportive substrate to complete the device. Cadmium telluride (CdTe) solar cells are the current lowest price thin film technology, industrially mass-produced, and cost-competitive with traditional non-renewable electric power. Part of the success of this technology relies on producing high electronic quality material in large-scale processes. Industrial deposition time of the CdTe active layer is ~ 30 seconds. However, additional CdCl2 chemical treatment, required to improve material electronic quality and device performance, adds ~ 30 minutes processing time. CdTe films can be considered a composite of well-ordered crystalline grains and grain boundary materials with properties of both impacting device performance. The role grain boundary structure plays on the electronic properties of CdTe will be studied with the ultimate intention of identifying as-deposited structures that enable reduction or elimination of the time-consuming CdCl2 process to lower cost. By combining advanced material deposition to control CdTe grain boundary characteristics, theoretical modeling of these grain boundary structures, and fabrication and processing of full CdTe solar cells links between CdTe layer characteristics and solar cell device performance will be uncovered. The work has implications for energy and other technological applications of national interest. The PIs and the PhD candidates will engage in outreach activities that will contribute to the education of local K-12 students and teachers, the general public, and industry. Technical Description: CdCl2 treatment modifies CdTe by promoting crystalline grain growth, reducing the impact of defects, and changing grain boundary chemistry by replacing ~50% of the boundary Te with Cl. The role grain boundary structure plays on the electronic properties of CdTe will be studied with the ultimate intention of identifying as-deposited microstructures that enable reduction or elimination of the time-consuming CdCl2 process to lower cost. CdTe films will be sputter deposited with the substrate normal at an oblique angle relative to the deposition flux, producing material with controllable grain orientation and small angle grain boundaries. In situ real time spectroscopic ellipsometry will be used to monitor, study, and control the growth evolution of these films. Density functional theory calculations will be performed to identify energetics of crystallite orientations and grain boundaries. Controlled orientation CdTe will be incorporated into single junction solar cells as either full or partial replacement layers for normal incidence sputtered or close space sublimated CdTe. Impact of CdCl2 treatment and processing time on performance will be identified for devices with controlled orientation CdTe. Fundamental connections between grain structure and device performance will be evaluated, with grain boundary structure enabling reduced CdCl2 processing times identified

摘要标题：晶界在CdTe太阳能电池性能中的作用非技术描述：太阳能是一种可再生能源，对环境的影响很小，而且潜在的成本很低，因此有兴趣满足日益增长的全球能源需求。在薄膜太阳能技术中，电力来自于器件的微米-薄半导体有源层吸收的入射光，以及支撑基板上的一堆其他薄膜层，以完成器件。碲化镉(CdTe)太阳能电池是目前价格最低的薄膜技术，可工业化大规模生产，与传统的不可再生电力相比具有成本竞争力。这项技术的成功部分依赖于在大规模工艺中生产高质量的电子材料。有源层的工业沉积时间为~30秒。然而，为了提高材料电子质量和器件性能，额外的氯化镉化学处理增加了大约30分钟的处理时间。CdTe薄膜可以被认为是由有序的晶体和晶界材料组成的复合材料，具有影响器件性能的两种特性。将研究晶界结构对CdTe电子性质的作用，最终目的是确定沉积结构，使之能够减少或消除耗时的CdCl2工艺，以降低成本。通过结合先进的材料沉积来控制CdTe晶界特性，这些晶界结构的理论建模，以及全CdTe太阳电池的制造和加工，将揭示CdTe层特性和太阳能电池器件性能之间的联系。这项工作对能源和其他涉及国家利益的技术应用具有影响。PIs和博士候选人将参与有助于当地K-12学生和教师、普通公众和工业界的教育的外展活动。技术描述：氯化镉处理通过促进晶体生长，减少缺陷的影响，并通过用氯取代~50%的晶界Te来改变晶界化学，从而对CdTe进行改性。将研究晶界结构对CdTe电子性质的作用，最终目的是识别沉积时的微结构，以减少或消除耗时的CdCl2工艺，以降低成本。在衬底与沉积通量成斜角的情况下，溅射沉积CdTe薄膜，得到晶向可控、晶界小角度的材料。现场实时椭圆偏振光谱将被用来监测、研究和控制这些薄膜的生长演化。将进行密度泛函理论计算以确定微晶取向和晶界的能量学。可控取向的CdTe将作为垂直入射溅射或近空间升华的CdTe的全部或部分替换层加入到单结太阳电池中。对于具有受控取向的CdTe器件，将确定氯化镉处理和处理时间对性能的影响。将评估晶界结构和器件性能之间的基本联系，并确定晶界结构能够减少CdCl2处理时间