Enhancing Quantum Efficiency of Thin Film Solar Cells via Joint Characterization of Radiation and Recombination

薄膜太阳能电池处于光电子技术创新的前沿。然而，薄膜太阳能电池的效率明显低于体电池，限制了其应用规模。基于结构修饰的光捕获方案已被用于提高纳米级光伏器件的效率。这些方案以复杂的方式影响薄半导体的辐射和电学特性。这些影响既没有准确的模型，也不是众所周知的。这项研究填补了这一知识空白，通过模拟光捕获的辐射和电效应。所提出的模型将是多样的，全面的，比现有的文献更准确。通过使用改进的模型，新的架构可以设计的太阳能电池设备具有增强的转换效率和减少的能量回收期相比，国家的最先进的技术，这是非常有价值的美国经济。此外，这项工作导致更好地理解纳米结构修饰的辐射效应，这在光电子学之外的纳米级辐射应用中是必不可少的。本项目研究系统地提高纳米级薄膜太阳能电池量子效率的方法。为此，研究了纳米尺度下光陷效应辐射的基本原理。解析模型制定用于解释辐射在非均匀半导体沿着与电载流子复合。的辐射模型是基于改进的估计的光学状态的局部密度在伪周期性金属介电表面和体图案的存在下，和精确估计的消光截面在等离子体纳米粒子的基础上改进的米氏散射使用数学形状配方和数据拟合。叠加辐射效应从多个机制进行建模，并结合现实的材料缺陷和物理缺陷的假设下的载流子输运模型。这项工作利用改进的模型设计结构，具有超越遍历极限的宽带/角光吸收，量子效率接近散装电池的极限。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Thin film solar cells are at the forefront of innovation in photovoltaics technology. However, the efficiency of thin film solar cells is significantly lower than bulk cells, limiting the scale of their application. Light trapping schemes based on structural modifications have been used to improve the efficiency of nano-scale photovoltaic devices. These schemes affect both radiative and electrical characteristics of thin semiconductors in complex ways. These effects are neither accurately modeled nor well known. This research fills this knowledge gap by modeling the combined radiative and electrical effects of light trapping. The proposed models will be diverse, comprehensive and more accurate than the existing literature. By using the improved models, novel architectures can be designed for solar cell devices with enhanced conversion efficiencies and reduced energy payback periods compared to the state-of-the-art technology which is highly valuable to the US economy. Additionally, the work leads to better understanding of the radiative effects of nano-structural modifications which is imperative in nano-scale radiation applications beyond photovoltaics.This project investigates methods to systematically enhance the quantum efficiency of nano-scale thin film solar cells. To this end, fundamentals of light-trapping affected radiation at nano-scale are studied. Analytical models are formulated for explaining radiation in non-homogenous semiconductors along with electrical carrier recombination. The radiative models are based on improved estimations of the local density of optical states in the presence of pseudo-periodic Metallo-dielectric surface and bulk patterns, and accurate estimation of extinction cross-section in plasmonic nano-particles based on improvements of Mie scattering using mathematical shape formulations and data fitting. Overlaying radiative effects from multiple mechanisms are modeled and combined with carrier transport models under realistic material imperfections and physical defects assumptions. The work utilizes the improved models to design structures with broad-band/angle optical absorption beyond the ergodic limits, and quantum efficiencies approaching the limits of bulk cells.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.