Influence of Reduced Gas Flow Rates on the Sheet Resistance of Boron-Doped Layers Performed in a Compact Furnace

Manufacturing processes for bifacial TOPCon and PERC solar cells have been investigated to increase efficiency and reduce costs. Considering that quartz tube furnaces are usually employed to produce doped layers, in this work, we analyse the influence of reduced gas flow rates on the sheet resistance of boron-doped layers formed in a new compact furnace to produce the emitter of TOPCon and the BSF of bifacial PERT solar cells. A compact furnace prototype was developed according to the granted patent BR102012030601-8. The spin-coating method was used to deposit a boron solution on one face of the Si wafer, and diffusion was carried out with reduced and baseline gas flow rates. The average sheet resistance (Rₛₕ) of B-BSF produced with oxygen and nitrogen flow rates reduced, respectively, by 50% and 90% ranged from 43.3 to 48.6 Ω/sq, and the standard deviation (SD) was lower than 3.2%. Although the average Rₛₕ from 103 to 158 Ω/sq produced with baseline gas flow rates was higher, the SD was 2% - 11%. The emitter formed with reduced gas flow rates presented a Rₛₕ from 88 to 118 Ω/sq with a SD between 4% and 7%. Additionally, the boron concentration in the emitter increased slightly at depths greater than 0.45 μm.