Development and characterization of resource-saving doping processes for industrial silicon solar cells

Abstract: Thermal processes account for a significant share of process cost and energy consumption during the manufacturing of passivated emitter and rear (PERC) and tunnel oxide passivated contacts (TOPCon) solar cells. This thesis investigates high throughput approaches for the thermal processes diffusion and/or oxidation in the manufacturing sequence of PERC and TOPCon solar cells. This is achieved by increasing the number of wafers in the process chamber by using wafer stacks with the wafer surfaces in direct contact rather than classical quartz boats with several mm spacing. Compared to state-of-the-art processing, the throughput can be drastically increased which makes the manufacturing more cost-effective and sustainable.
For PERC solar cells, the high temperature stack oxidation (HiTSOx) approach has been developed. This approach combines a shortened phosphorus oxychloride (POCl3) diffusion with a stacked oxidation process. Here, the stack oxidation generates the final emitter doping profile from the phosphorus already incorporated in the silicon after the POCl3 diffusion through dopant redistribution and activation. Simultaneously a silicon dioxide surface passivation layer forms on the wafer surface. With this approach, PERC solar cells are fabricated that feature a similar energy conversion efficiency compared to state-of-the-art processing with 22.2%. With HiTSOx, the cost of ownership (COO) of the thermal processes is reduced by 44%, saving 50% of the specific power consumption.
The oxide layer grown during the HiTSOx process exhibits a high uniformity of below 6% standard deviation over the surface of a 156.75 mm sized wafer. This is a surprising result taking into account that the wafers are directly stacked during the process. Therefore, a model describing the new oxidation process was developed. Numerical simulation of the oxide growth and gas flow within the gap between the stacked wafers reveal that the consumption of oxygen creates a reduced local pressure in the wafer gap, forcing further oxygen to flow into the wafer gap. The numerical simulation is verified by special experiments.
For TOPCon solar cells, a stacked boron diffusion process is developed. Prior to the stack diffusion process, a borosilicate glass layer is deposited by atmospheric chemical vapor deposition (APCVD) as a dopant source. The above-described uniform surface oxidation in the wafer gap yields a homogeneous doping result, despite a strong sensitivity of boron diffusion to oxygen. In addition, the results indicate that the temperature uniformity in the wafer stack is of high importance. Using stack diffusion, TOPCon solar cells with energy conversion efficiency above 23% are fabricated only slightly below the references fabricated with the classical process. Further, the COO of the
doping process is reduced by 19 to 25%, depending on the borosilicate glass deposition technology, and specific energy consumption by up to 55%, enabling a more sustainable solar cell manufacturing

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2023

Klassifikation und Themen

• Klassifikation: Elektrotechnik, Elektronik
• Schlagwort: Silicium ; Solarzelle ; Diffusion ; Emitter ; Passivierung ; Kontaktieren

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2023
• Urheber: Meßmer, Marius
• Beteiligte Personen und Organisationen: Glunz, Stefan ; Glunz, Stefan ; Kray, Daniel ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Weitere Informationen

• DOI: 10.6094/UNIFR/238628
• URN: urn:nbn:de:bsz:25-freidok-2386284
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 25.03.2025, 13:49 MEZ