Silicon Metal-Insulator-Semiconductor Photovoltaics with Atomic Layer Deposited Interfacial Layers

太阳是地球上最丰富的可持续能源的潜在来源。 用于发电的太阳能电池需要吸收太阳能并将其光子转化为电子的材料，这一过程称为光电子学。 降低太阳能光伏能量转换系统的每瓦成本是一个长期目标，可以使太阳能得到更广泛的采用。 特别是，如果能够找到实现高太阳能转换效率的材料特性组合，薄膜太阳能电池的制造成本将比晶体硅太阳能电池更低。本课题的目的是研究既能实现低成本加工，又能实现高太阳能转换效率的薄膜太阳能光电池的新型层状结构。 这些新的分层结构基于电子材料的金属-绝缘体-半导体夹层结构，在它们各自的材料边界处具有可以有利地改变太阳能电池的整体电子结构和性质的行为，从而导致改进的性能。这项研究的创新之处在于，将使用先进的技术以原子级精度将这些层存款在彼此之上，以便可以更仔细和更有见地地研究这些属性。 与该项目相关的教育活动包括与当地科学中心合作开展社区外展计划，并制作视频，以动画形式展示光伏器件运行背后的物理效应。本研究的总体目标是确定在金属-硅材料中插入介电隧道层引起势垒高度变化和其他界面电子变化的潜在机制。绝缘体-半导体光致发光（PV）。金属-绝缘体-半导体结构将通过薄膜沉积和界面改性技术制造，这些技术允许前所未有的界面控制水平。这种水平的控制将使固定电荷，分子表面功能化，原子层沉积（ALD）化学，氢处理，和ALD双层MIS结构的基本行为的调查。这些现象的势垒高度和界面电子品质因数的改善光伏器件的具体影响将被量化。 不同金属氧化物双层内的偶极子也将用于控制势垒高度。 通过改变固定电荷密度和绝缘体厚度的实验，并将这些实验结果与理论模拟进行比较，研究固定电荷对电子特性的影响。 分子表面功能化和界面处的氢提供了额外的合成控制，并且将确定它们使界面电子缺陷最小化的能力。通过比较电子测量，低能离子散射，和光电子能谱测量，层混合，偶极子强度和界面陷阱密度之间的关键关系将得到阐明。因此，该研究将推进对基本物理机制的基本理解，同时提高新一代金属-绝缘体-半导体薄膜太阳能光伏器件的能量转换品质因数。

The sun represents the most abundant potential source of sustainable energy on earth. Solar cells for producing electricity require materials that absorb the sun's energy and convert its photons to electrons, a process called photovoltaics. Lowering the cost per watt for solar photovoltaic energy conversion systems is a long-standing goal that could enable more widespread adoption of solar energy. In particular, thin-film solar cells can be made cheaper than crystalline silicon-based solar cells if the right combination of material properties for high solar energy conversion efficiency can be found. The goal of this project is to investigate new layered structures for thin-film solar photovoltaics that potentially offer both low-cost processing and high solar energy conversion efficiency. These new layered structures, based on a metal-insulator-semiconductor sandwich of electronic materials, have behavior at their respective material boundaries that may favorably change the overall electronic structure and properties of the solar cell, resulting in improved performance. The innovative aspect of this research is that advanced techniques will be used to deposit these layers on top of one another with atomic level precision so that these properties can be more carefully and insightfully studied. The educational activities associated with this project include the development of a community outreach program with a local science center and the production of videos that animate the effects of physics behind the operation of photovoltaic devices.The overall goal of this research is to identify the underlying mechanisms that induce barrier height modifications and other interfacial electronic changes by insertion of dielectric tunnel layers in the context of metal-insulator-semiconductor photovoltaics (PV). Metal-insulator-semiconductor structures will be fabricated by film deposition and interface modification techniques that allow for an unprecedented level of interfacial control. This level of control will enable investigation of the fundamental behavior of fixed charges, molecular surface functionalization, atomic layer deposition (ALD) chemistry, hydrogen treatment, and ALD bilayers in MIS structures. The specific influence of these phenomena on barrier heights and interfacial electronic figures of merit relevant for improving PV devices will be quantified. Dipoles within bilayers of dissimilar metal oxides will also be used to control barrier heights. The impact of fixed charge on electronic properties will be investigated by varying fixed charge density and insulator thickness experimentally, and comparing these experimental results with theoretical simulations. Molecular surface functionalization and hydrogen at interfaces provide additional synthetic control, and their ability to minimize interfacial electronic defects will be determined. By comparing electronic measurements, low-energy ion scattering, and photoelectron spectroscopy measurements, critical relationships between layer mixing, dipole strength, and interface trap densities will be elucidated. Thus, the research will advance fundamental understanding of the underlying physical mechanisms while improving energy conversion figures of merit in a new generation of metal-insulator-semiconductor, thin-film solar PV devices.