Transparent conductors for thin film solar cells

薄膜光伏面板、智能手机和触摸屏电视显示器等设备依赖于薄膜透明导电氧化物（TCO）来实现电接触。透明导体通常沉积在玻璃内表面上，并通过封装在器件内而受到保护。然而，在一些太阳能电池应用中，它是暴露于环境的薄膜叠层的一部分。在这两种情况下，TCO保持其性能随着时间的推移是很重要的。TCO的性能由其光学、电学和结构特性决定。用于太阳能应用的最重要的TCO是铟锡氧化物（ITO）、铝掺杂氧化锌（AZO）和铟掺杂氧化锌（IZO）。使用组合溅射的ITO组合物的范围将被制造和映射其光学和电学性能。这些特性将与太阳能应用的要求相匹配。一种应用是在可见光波长中抗反射但在红外线中反射的涂层。反射红外线有助于保持模块冷却，提高效率和模块可靠性。折射率色散和吸收是其关键性能参数。另一个潜在的重要应用是双面薄膜太阳能电池的开发，其中薄层电阻和载流子浓度的电性能是重要的。本项目将使用实验室环境应力测试和真实的户外暴露测试的组合，以确定是否发生降解。实验室测试将包括湿热（85 ℃，85%湿度）、紫外线暴露、温度循环、湿度冻结等。除了薄层电阻的电气测试外，还将使用扫描电子显微镜（SEM）和X射线光电子能谱（XPS）研究化学和结构涂层降解。

Devices such as thin film photovoltaic panels, smartphones and touch screen television displays rely on a thin film transparent conducting oxide (TCO) to make electrical contact. The transparent conductor is usually deposited on the inside glass face and is protected by being encapsulated within the device. However, in some solar cell applications it is part of a thin film stack that is exposed to the environment. In both cases, it is important that the TCO retains its performance over time.The performance of a TCO is determined by its optical, electrical and structural properties. The most important TCO's for solar applications are Indium Tin Oxide (ITO), Aluminium doped Zinc Oxide (AZO) and Indium doped Zinc Oxide (IZO). Using combinatorial sputtering a range of ITO compositions will be fabricated and mapped for their optical and electrical properties. These properties will be matched to the requirements of solar applications. One application is a coating that is anti-reflecting in the visible wavelengths but reflecting in the infra-red. Reflecting the infra-red helps to keep the module cool, improving efficiency and module reliability. The refractive index dispersion and absorption are the key performance parameters. Another potentially important application is the development of a bifacial thin film solar cell where the electrical properties of sheet resistance and carrier concentration are important.The stability of transparent conductors when exposed to the atmosphere has not been established. This project will use a combination of Laboratory environmental stress tests and real outdoor exposure tests to determine if degradation occurs. The Laboratory tests will include damp heat (85C, 85% humidity), UV exposure, temperature cycling, humidity freeze etc. In addition to electrical tests of sheet resistance, the chemical and structural coating degradation will be investigated using Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).