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

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

Research output: Contribution to conferencePaper


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.
Original languageAmerican English
Number of pages3
StatePublished - 2021
Event38th European Photovoltaic Solar Energy Conference and Exhibition -
Duration: 6 Sep 202110 Sep 2021


Conference38th European Photovoltaic Solar Energy Conference and Exhibition

NREL Publication Number

  • NREL/CP-5900-80910


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


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