Novel Poly-Si:Ga/SiOx Passivating Contacts through Non-Equilibrium Doping

Conference · Fri Sep 10 04:00:00 EDT 2021

DOI:https://doi.org/10.4229/EUPVSEC20212021-2BO.11.4· OSTI ID:1968450

Chen, Kejun; Napolitani, Enrico; de Tullio, Matteo; Jiang, Chun-Sheng; Theingi, San; Nemeth, William; Page, Matthew; Stradins, Pauls; Agarwal, Sumit; Young, David L.

Poly-Si/SiOx passivating contacts are one of the key enablers for high-efficiency, low-cost c-Si solar cells. In recent years, record devices have reached efficiencies of 26% in the laboratory and 25% in the industry. The current cell structure utilizing a tunneling oxide passivating contact structure with a back phosphorus-doped poly- Si/SiOx passivating contact and a front boron diffused emitter suffers from large emitter recombination. Thus, replacing the front B diffused emitter with a p-type passivating contact is a route to overcome this deficiency. This gives rise to front/back poly-Si based passivating contacts. To address the low passivation performance of the B-doped poly-Si passivating contacts, we replace B with Ga as a novel p-type dopant to avoid dopant accumulation in the tunneling oxide, which is known to lead to large degradation loss in passivation quality. Here, we introduce a non-equilibrium method via pulsed laser melting to thermally melt and recrystallize the poly-Si and redistribute the dopants, achieving doping concentrations above the solid solubility limit (~4E19 cm-3). We demonstrate a good passivation quality with an iVoc of 721 mV with an active Ga doping concentration in poly-Si >1020 cm-3. Furthermore, we show a low contact resistivity of 33.2 +/- 9.3 mO cm2 using a diode model calculation. Finally, cross-section scanning spreading resistance microscopy was performed to determine the resistance profile across the non-homogeneously doped poly-Si layer.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1968450
• Report Number(s): NREL/CP-5900-80910; MainId:78688; UUID:7684ff18-21ad-4826-a68a-213893a8e8a5; MainAdminID:62878
• Country of Publication: United States
• Language: English

Related Subjects

PV
SOLAR ENERGY
c-Si
contact resistivity
passivated contacts
photovoltaic
polysilicon
pulsed laser melting