Shi Dai, Zeng Yang, Shen Wenzhong
Institute of Solar Energy, and Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China.
Sci Rep. 2015 Nov 13;5:16504. doi: 10.1038/srep16504.
Perovskite/c-Si tandem solar cells (TSCs) have become a promising candidate in recent years for achieving efficiency over 30%. Although general analysis has shown very high upper limits for such TSCs, it remains largely unclear what specific optical structures could best approach these limits. Here we propose the combination of perovskite/c-Si tandem structure with inverted nanopyramid morphology as a practical way of achieving efficiency above 31% based on realistic solar cell parameters. By full-field simulation, we have shown that an ultra-low surface reflectance can be achieved by tuning the pyramid geometry within the range of experimental feasibility. More importantly, we have demonstrated that the index-guided modes can be excited within the top cell layer by introducing a TCO interlayer that prevents coupling of guided light energy into the bottom cell. This light trapping scheme has shown superior performance over the Bragg stack intermediate reflector utilized in previous micropyramid-based TSCs. Finally, by controlling the coupling between the top and bottom cell through the thickness of the interlayer, current generation within the tandem can be optimized for both two- and four-terminal configurations, yielding efficiencies of 31.9% and 32.0%, respectively. These results have provided useful guidelines for the fabrication of perovskite/c-Si TSCs.
近年来，钙钛矿/晶体硅串联太阳能电池（TSCs）已成为实现效率超过30%的一个有前景的候选方案。尽管一般分析表明此类TSCs具有非常高的上限，但在很大程度上仍不清楚哪种特定的光学结构最能接近这些极限。在此，我们提出将具有倒置纳米金字塔形态的钙钛矿/晶体硅串联结构相结合，作为一种基于实际太阳能电池参数实现效率高于31%的实用方法。通过全场模拟，我们表明在实验可行性范围内调整金字塔几何形状可以实现超低表面反射率。更重要的是，我们证明通过引入一个防止导波光能量耦合到底部电池的透明导电氧化物（TCO）中间层，可以在顶部电池层内激发折射率引导模式。这种光捕获方案已显示出比先前基于微金字塔的TSCs中使用的布拉格堆叠中间反射器更优越的性能。最后，通过控制中间层厚度来控制顶部和底部电池之间的耦合，可以针对双端和四端配置优化串联电池内的电流产生，分别产生31.9%和32.0%的效率。这些结果为钙钛矿/晶体硅TSCs的制造提供了有用的指导。
