In this paper, a record-breaking efficiency of 12.3% is experimentally demonstrated for a flexible free-standing, 2.7-μm-thick ultrathin crystalline silicon (c-Si) solar cell, which is the highest ever-reported sub 3 μm c-Si solar cells. The first breakthrough of this study is achieving an exceptionally small exposure feature size of 350 nm using photolithography stepper without any additional stringent requirements on wafer flatness or depth of focus (DOF) of the projection system. This small exposure feature size enables the fabrication of a light-trapping scheme: a design of close-packed 700-nm-period touching inverted-pyramid nanostructures for enhanced light absorption. Furthermore, to reduce contact recombination, this work is also first to report the integration of nickel oxide (NiO_x) as hole-selective contacts in conjunction with the nano-structure light trapping scheme on a free-standing ultrathin cell. The efficacy of these two mechanisms to enhance ultrathin c-Si cell efficiency is characterized in terms of the short circuit current density and open circuit voltage. The free-standing cell also shows good mechanical flexibility and compliance. In addition to demonstrating silicon-compatible fabrication, this work shows the potential of ultrathin c-Si technology to not only reduce material cost, but also maintain competitive device performance.

本文通过实验证明了一种灵活的自立式2.7μm厚超薄晶体硅（c-Si）太阳能电池的破纪录效率，达到了12.3％，这是有史以来最高的亚3μmc-硅太阳能电池。这项研究的第一个突破是使用光刻步进器实现了350 nm的极小的曝光特征尺寸，而对晶圆的平坦度或投影系统的景深（DOF）没有任何其他严格要求。这种小的曝光特征尺寸使得能够制造光陷阱方案：紧密堆积的700 nm周期触摸倒金字塔纳米结构的设计，可增强光吸收。此外，为减少接触复合，这项工作还首次报道了氧化镍（NiO _x）作为空穴选择性接触，并与独立式超薄电池上的纳米结构光捕获方案结合使用。这两种机制提高超薄c-Si电池效率的功效均以短路电流密度和开路电压为特征。独立式电池还显示出良好的机械柔韧性和顺应性。除了演示与硅兼容的制造工艺外，这项工作还显示出超薄c-Si技术的潜力，不仅可以降低材料成本，而且还能保持具有竞争力的器件性能。