Abstract We report thin-film InAs/GaAs quantum dot (QD) solar cells with n − i − p + deep junction structure and planar back reflector fabricated by epitaxial lift-off (ELO) of full 3-in wafers. External quantum efficiency measurements demonstrate twofold enhancement of the QD photocurrent in the ELO QD cell compared to the wafer-based QD cell. In the GaAs wavelength range, the ELO QD cell perfectly preserves the current collection efficiency of the baseline single-junction ELO cell. We demonstrate by full-wave optical simulations that integrating a micro-patterned diffraction grating in the ELO cell rearside provides more than tenfold enhancement of the near-infrared light harvesting by QDs. Experimental results are thoroughly discussed with the help of physics-based simulations to single out the impact of QD dynamics and defects on the cell photovoltaic behavior. It is demonstrated that non radiative recombination in the QD stack is the bottleneck for the open circuit voltage ( V oc ) of the reported devices. More important, our theoretical calculations demonstrate that the V oc offset of 0.3 V from the QD ground state identified by Tanabe et al., 2012, from a collection of experimental data of high quality III-V QD solar cells is a reliable – albeit conservative – metric to gauge the attainable V oc and to quantify the scope for improvement by reducing non radiative recombination. Provided that material quality issues are solved, we demonstrate – by transport and rigorous electromagnetic simulations – that light-trapping enhanced thin-film cells with twenty InAs/GaAs QD layers reach efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible.

中文翻译：

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通过外延剥离制造的光捕获增强薄膜 III-V 量子点太阳能电池

摘要 我们报告了薄膜 InAs/GaAs 量子点 (QD) 太阳能电池，具有 n - i - p + 深结结构和由全 3 英寸晶圆的外延剥离 (ELO) 制造的平面背反射器。外部量子效率测量表明，与基于晶片的 QD 电池相比，ELO QD 电池中的 QD 光电流增强了两倍。在 GaAs 波长范围内，ELO QD 电池完美地保持了基线单结 ELO 电池的电流收集效率。我们通过全波光学模拟证明，在 ELO 单元背面集成微图案衍射光栅可将 QD 采集的近红外光增强十倍以上。在基于物理的模拟的帮助下，对实验结果进行了彻底的讨论，以找出 QD 动力学和缺陷对电池光伏行为的影响。结果表明，QD 堆栈中的非辐射复合是所报告器件开路电压 (V oc ) 的瓶颈。更重要的是，我们的理论计算表明，从 Tanabe 等人于 2012 年确定的 QD 基态的 0.3 V V oc 偏移量是可靠的——尽管是保守的– 衡量可达到的 V oc 并通过减少非辐射复合来量化改进范围的度量标准。只要解决了材料质量问题，我们通过传输和严格的电磁模拟证明，具有 20 个 InAs/GaAs QD 层的光捕获增强型薄膜电池在非集中光和环境温度下可达到 28% 以上的效率。如果可以充分利用光子回收，30%的效率被认为是可行的。