Rapid Thermal Annealing of p-Type Polysilicon Passivated Contacts Silicon Solar Cells

• Published in: IEEE journal of photovoltaics Vol. 13; no. 3; pp. 1 - 10
• Main Authors: Sinha, Arpan, Dasgupta, Sagnik, Rohatgi, Ajeet, Gupta, Mool C.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.05.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Annealing; Annealing furnaces; Atmosphere; blister; Blistering; Blisters; Crystallization; Degradation; Electric contacts; Furnaces; Heating systems; Luminous intensity; Nitrogen; Optical radiation; Oxidation; Passivation; Photovoltaic cells; Polysilicon; Rapid thermal annealing; rapid thermal annealing (RTA); Silicon; Solar cells; Temperature dependence; tunnel oxide passivated contact (TOPCon); Valence
• ISSN: 2156-3381; 2156-3403
• DOI: 10.1109/JPHOTOV.2023.3241790

The carrier selective contacts Si solar cells based on tunnel oxide passivated contact (TOPCon) have provided an efficiency of over 25%, and the large-scale production is planned. One of the crucial steps in TOPCon solar cells fabrication is furnace annealing at around 875 °C. We have investigated the rapid thermal annealing (RTA) for TOPCon solar cells. We discovered that the RTA carried out in air showed much fewer hydrogen-induced blisters than in the N 2 atmosphere. Second, the optical radiation and heat generated in RTA had a significant effect on the degradation of iV oc . The RTA with a SiN x :H layer on top of polysilicon generated iV oc of 706 mV. The mechanism of degradation under air versus nitrogen atmosphere and the effect of high-intensity light during the annealing process were inferred through various characterizations, such as surface morphology, surface passivation, crystallinity determination, chemical compositional changes, electrical sheet resistances, and oxidation state of ultrathin SiO x . The TOPCon after air RTA performed better than in nitrogen, optimally at 825 °C. Forming gas annealing further improved the iV oc . Crystallization and sheet resistance were dependent on the annealing temperature and time.