Optimizing metal grating back reflectors for III-V-on-silicon multijunction solar cells

Multi-junction solar cells allow to utilize sunlight more effectively than single junction solar cells. In our work, we present optical simulations of III-V-on-silicon solar cells with a metal grating at the back, which experimentally have reached more than 33% power conversion efficiency. First, we perform simulations with the finite element method and compare them with experimental data to validate our model. We find that accurately modeling the investigated geometrical structure is necessary for best agreement between simulation and experimental measurements. Then, we optimize the grating for maximized light trapping using a computationally efficient Bayesian optimization algorithm. The photo current density of the limiting silicon bottom cell is improved from 13.48 mA/cm2 for the experimental grating to 13.85 mA/cm2 for the optimized metal grating. Investigation of all geometrical optimization parameters of the grating (period, height, …) shows that the structure is most sensitive towards the period, a parameter highly controllable in manufacturing by inference lithography.
The data is provided as a ZIP archive containing the raw simulation results from FEM calculations for the backside grating and TMM calculations for the planar front side as well as EQE and reflection measurements of the experimental cells used as a benchmark. Please refer to the readme file included in the archive for details about the data structure.
Python code is supplied under DOI:10.5281/zenodo.5013230 that allows to generate the figures in the Optics Express publication “Optimizing metal grating back reflectors for III-V-on-silicon multijunction solar cells.” from the simulation raw data.

多结太阳能电池（Multi-junction solar cells）相较单结太阳能电池（single junction solar cells），可更高效地利用太阳光。在本研究中，我们针对背面带有金属光栅的硅基III-V族太阳能电池（III-V-on-silicon solar cells）开展光学仿真，该类电池的实测功率转换效率已突破33%。首先，我们采用有限元法（Finite Element Method, FEM）开展仿真，并将仿真结果与实验数据对比以验证模型的有效性。研究表明，精准建模所考察的几何结构，是实现仿真与实验测量最佳匹配的必要前提。随后，我们借助计算效率优异的贝叶斯优化算法（Bayesian optimization algorithm），对光栅进行优化以实现最大程度的光俘获。经优化后的金属光栅，可将限流硅底子电池的光电流密度从实验光栅下的13.48 mA/cm²提升至13.85 mA/cm²。对光栅所有几何优化参数（周期、高度等）的分析显示，该结构对周期参数最为敏感，而该参数可通过压印光刻技术在制造过程中实现高精度可控。

本数据集以ZIP压缩包形式提供，包含背面光栅的有限元法仿真原始结果、平面正面的传输矩阵法（Transfer Matrix Method, TMM）仿真原始结果，以及作为基准的实验电池的外量子效率（External Quantum Efficiency, EQE）与反射率测量数据。请查阅压缩包内的README文件，以了解数据集的具体结构细节。

本研究配套的Python代码已上传至Zenodo平台，数字对象标识符（Digital Object Identifier, DOI）为10.5281/zenodo.5013230，该代码可基于仿真原始数据复现发表于《光学快报》（Optics Express）的论文"Optimizing metal grating back reflectors for III-V-on-silicon multijunction solar cells"中的相关图表。