Photovoltaic (PV) conversion of solar energy starts to give an appreciable contribution to power generation in many countries, with more than 90% of the global PV market relying on solar cells based on crystalline silicon (c-Si). The current efficiency record of c-Si solar cells is 26.7%, against an intrinsic limit of ~29%. Current research and production trends aim at increasing the efficiency, and reducing the cost, of industrial modules. In this paper, we review the main concepts and theoretical approaches that allow calculating the efficiency limits of c-Si solar cells as a function of silicon thickness. For a given material quality, the optimal thickness is determined by a trade-off between the competing needs of high optical absorption (requiring a thicker absorbing layer) and of efficient carrier collection (best achieved by a thin silicon layer). The efficiency limits can be calculated by solving the transport equations in the assumption of optimal (Lambertian) light trapping, which can be achieved by inserting proper photonic structures in the solar cell architecture. The effects of extrinsic (bulk and surface) recombinations on the conversion efficiency are discussed. We also show how the main conclusions and trends can be described using relatively simple analytic models. Prospects for overcoming the 29% limit by means of silicon/perovskite tandems are briefly discussed.

在许多国家，太阳能的光伏（PV）转换开始为发电做出重要贡献，全球90％以上的PV市场依靠基于晶体硅（c-Si）的太阳能电池。c-Si太阳能电池的当前效率记录为26.7％，而固有极限为〜29％。当前的研究和生产趋势旨在提高工业模块的效率并降低成本。在本文中，我们回顾了主要概念和理论方法，这些概念和理论方法可以计算c-Si太阳能电池的效率极限与硅厚度的关系。对于给定的材料质量，最佳厚度取决于高光吸收（需要更厚的吸收层）和高光吸收的竞争需求之间的权衡。有效的载流子收集（最好通过薄硅层实现）。可以在最佳（朗伯）光陷阱假设下通过求解输运方程来计算效率极限，这可以通过在太阳能电池架构中插入适当的光子结构来实现。讨论了外在（本体和表面）重组对转化效率的影响。我们还展示了如何使用相对简单的分析模型来描述主要结论和趋势。简要讨论了通过硅/钙钛矿薄膜克服29％极限的前景。