Sufficiently deep local back-surface-fields (LBSF) are crucial for achieving low contact recombination and thus high solar cell efficiencies in passivated emitter and rear contact (PERC) solar cells. In this article, we investigate spatial variations of LBSF thickness 1) across dashed contacts, 2) between lateral positions within a cell, and 3) from cell to cell. The objective of this experimental study is to proof the impact of LBSF thickness on open-circuit voltage in PERC solar cells. Our measurements and analysis of variance (ANOVA) reveal that variations in LBSF thickness across dashed contacts exceed observed variations in LBSF thickness between lateral positions within a cell as well as cell-to-cell variations. Thus, we statistically treat all LBSF measurements of a single experimental group of PERC solar cells as one population of measurements. The two investigated experimental sets of PERC cells fired using different fast-firing profiles show a difference in LBSF thickness of about 1 μm. The resulting difference in open-circuit voltages arises to 1.3 mV. ANOVA-based analysis shows for our experimental samples that at least 19 random measurements are necessary in order to resolve LBSF thickness difference of 0.5 μm with sufficient statistical significance.

中文翻译：

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局部背表面场厚度对 PERC 太阳能电池开路电压的影响：应用方差分析确定区分具有统计意义的平均 LBSF 值所需的关键样本大小的实验研究


足够深的局部背表面场 (LBSF) 对于实现低接触复合以及钝化发射极和背接触 (PERC) 太阳能电池的高太阳能电池效率至关重要。在本文中，我们研究了 LBSF 厚度的空间变化：1) 跨虚线接触，2) 单元内横向位置之间，以及 3) 单元之间。本实验研究的目的是证明 LBSF 厚度对 PERC 太阳能电池开路电压的影响。我们的测量和方差分析（ANOVA）表明，虚线接触处的 LBSF 厚度变化超过了细胞内横向位置之间以及细胞间变化观察到的 LBSF 厚度变化。因此，我们在统计上将单个 PERC 太阳能电池实验组的所有 LBSF 测量值视为一组测量值。使用不同快速烧成曲线烧成的两组所研究的 PERC 电池实验组显示 LBSF 厚度差异约为 1 μm。由此产生的开路电压差异达到 1.3 mV。基于方差分析的分析表明，对于我们的实验样品，至少需要 19 次随机测量才能解决 0.5 μm 的 LBSF 厚度差异并具有足够的统计显着性。