Broadband absorption enhancement in ultra-thin crystalline Si solar cells by incorporating metallic and dielectric nanostructures in the back reflector
Samart Jain, Valerie Depauw, Vladimir D. Miljkovic, Alexamder Dmitriev, Christos Trompoukis, Ivan Gordon, Pol van Dorpe, Ounsi El Daif
We propose a back-reflecting scheme in order to enhance the maximum achievable current in one micron thick crystalline silicon solar cells. We perform 3-dimensional numerical investigations of the scattering properties of metallic nanostructures located at the back side, and optimize them for enhancing absorption in the silicon layer. We validate our numerical results experimentally and also compare the absorption enhancement in the solar cell structure, both with quasi-periodic and random metallic nanostructures. We have looked at the interplay between the metallic nanostructures and an integrated back-reflector. We show that the combination of metallic nanoparticles and a metallic reflector results in significant parasitic absorption. We compared this to another implementation based on titanium dioxide nanoparticles which act as a lambertian reflector of light. Our simulation and experimental results show that this proposed configuration results in reduced absorption losses and in broadband enhancement of absorption for ultra-thin solar cells, paving the way to an optimal back reflector for thin film photovoltaics.
Broadband, efficient extraction of quantum light by a photonic device comprised of a metallic nano-ring and a gold back reflector
为了在应用中实现基于量子发射器的量子光源，期望提高单光子的提取效率。特别是控制发射的方向性和立体角是关键参数，例如，将单光子耦合到光纤中并将量子光中编码的信息长距离发送，用于量子通信应用。此外，量子发射体的辐射行为的基础研究，包括相干性和闪烁的研究，受益于这种改进的光子收集。通过Sttranski-Krastanov技术生长的量子点已经被证明是明亮、相干、不可区分的量子光发射的良好候选者。然而，与这些量子光源相关的挑战之一源于这样一个事实：发射波长可以从一个发射器到另一个发射器而变化。为此，不依赖于高品质因数光学腔的宽带光提取器将是期望的，使得不需要在量子点发射波长和用于增加光提取的谐振器之间进行调谐。在这里，我们表明，金属纳米环与金背反射器相结合，增加了单光子的收集效率，我们研究了量子点在空间上随机分布在纳米环内时，这种效果的统计。当比较具有金背反射器的设备中纳米环内外的发射器时，我们显示亮度平均增加约7.5倍，我们测量到每秒超过7 x 10^6个光子的计数率和高达85%+/-1%的单光子纯度。这些结果是实现用于量子通信应用的可扩展、宽带、易于制造的量子光源的重要步骤。
