高掺硼钝化触点的激光活化

IF 0.9 Q4 GEOCHEMISTRY & GEOPHYSICS
Saman Sharbaf Kalaghichi, Jan Hoß, R. Zapf‐Gottwick, J. Werner
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引用次数: 0

摘要

在硅太阳能电池中,钝化的选择性触点由高掺杂多晶硅(poly Si)和薄界面二氧化硅(SiO2)的双层组成。这种设计理念可以实现最高的效率。在这里,我们报告了一个选择性激光激活过程,导致在SiO2上高掺杂p++型多晶硅。在这种双层结构中,p++-聚硅层作为将生成的孔从体块传输到金属触点的层,因此需要对孔具有高导电性。高硼掺杂多晶硅层是实现高导电性的途径之一。在激光激活步骤中,激光脉冲熔化多晶硅层,随后硅熔体的快速冷却使电活性硼浓度超过固体溶解度极限。除了高导电性外,多晶硅层中的高活性硼浓度可以通过在Si蚀刻溶液中提供蚀刻停止层来实现p++ +-多晶硅/SiO2层的无掩膜图案,从而在蚀刻过程后产生局部结构的p++ +-多晶硅/SiO2。激光激活技术面临的挑战是不破坏薄SiO2,这就需要对激光工艺进行微调。为了找到最佳的加工窗口,我们在两种不同厚度dpoly Si (1 = 155 nm)和dpoly Si (2 = 264 nm)的多晶硅层上测试了0.7 J/cm2≤Hp≤5 J/cm2的激光脉冲能量密度(Hp)。最后,对于两种多晶硅层厚度,2.8 J/cm2≤Hp≤4 J/cm2的加工窗口在不破坏SiO2的情况下导致最高的薄片电导(Gsh)。对于测试的两种多晶硅层,使用这些Hp处理的大多数对称寿命样品都具有良好的钝化质量,具有高隐含开路电压(iVOC)和低饱和电流密度(J0)。最佳样品每边iVOC = 722 mV, J0 = 6.7 fA/cm2。这种低表面复合电流密度,以及伴随的掺杂谱测量表明,在激光过程中SiO2没有被破坏。我们还观察到钝化质量与测试的多晶硅层厚度无关。本研究结果表明,激光激活的p++-poly Si/SiO2不仅适合集成到先进的钝化接触式太阳能电池中,而且还提供了这些堆栈的无掩膜图案的可能性,大大简化了此类太阳能电池的生产。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Laser Activation for Highly Boron-Doped Passivated Contacts
Passivated, selective contacts in silicon solar cells consist of a double layer of highly doped polycrystalline silicon (poly Si) and thin interfacial silicon dioxide (SiO2). This design concept allows for the highest efficiencies. Here, we report on a selective laser activation process, resulting in highly doped p++-type poly Si on top of the SiO2. In this double-layer structure, the p++-poly Si layer serves as a layer for transporting the generated holes from the bulk to a metal contact and, therefore, needs to be highly conductive for holes. High boron-doping of the poly Si layers is one approach to establish the desired high conductivity. In a laser activation step, a laser pulse melts the poly Si layer, and subsequent rapid cooling of the Si melt enables electrically active boron concentrations exceeding the solid solubility limit. In addition to the high conductivity, the high active boron concentration in the poly Si layer allows maskless patterning of p++-poly Si/SiO2 layers by providing an etch stop layer in the Si etchant solution, which results in a locally structured p++-poly Si/SiO2 after the etching process. The challenge in the laser activation technique is not to destroy the thin SiO2, which necessitates fine tuning of the laser process. In order to find the optimal processing window, we test laser pulse energy densities (Hp) in a broad range of 0.7 J/cm2 ≤ Hp ≤ 5 J/cm2 on poly Si layers with two different thicknesses dpoly Si,1 = 155 nm and dpoly Si,2 = 264 nm. Finally, the processing window 2.8 J/cm2≤ Hp ≤ 4 J/cm2 leads to the highest sheet conductance (Gsh) without destroying the SiO2 for both poly Si layer thicknesses. For both tested poly Si layers, the majority of the symmetric lifetime samples processed using these Hp achieve a good passivation quality with a high implied open circuit voltage (iVOC) and a low saturation current density (J0). The best sample achieves iVOC = 722 mV and J0 = 6.7 fA/cm2 per side. This low surface recombination current density, together with the accompanying measurements of the doping profiles, suggests that the SiO2 is not damaged during the laser process. We also observe that the passivation quality is independent of the tested poly Si layer thicknesses. The findings of this study show that laser-activated p++-poly Si/SiO2 are not only suitable for integration into advanced passivated contact solar cells, but also offer the possibility of maskless patterning of these stacks, substantially simplifying such solar cell production.
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来源期刊
Solar-Terrestrial Physics
Solar-Terrestrial Physics GEOCHEMISTRY & GEOPHYSICS-
CiteScore
1.50
自引率
9.10%
发文量
38
审稿时长
12 weeks
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