Large-area bifacial n-TOPCon solar cells with in situ phosphorus-doped LPCVD poly-Si passivating contacts

• Published in: Solar energy materials and solar cells 2022-03, Vol.236, p.111544, Article 111544
• Main Authors: Fırat, Meriç, Sivaramakrishnan Radhakrishnan, Hariharsudan, Payo, María Recamán, Choulat, Patrick, Badran, Hussein, van der Heide, Arvid, Govaerts, Jonathan, Duerinckx, Filip, Tous, Loic, Hajjiah, Ali, Poortmans, Jef
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; Contact potentials; Cytology; Emitters; Energy conversion efficiency; Film thickness; In situ phosphorus doping; Laminates; Low pressure; LPCVD; Metallizing; Open circuit voltage; Passivating contacts; Phosphorus; Photovoltaic cells; Polysilicon; Recombination; Screen printing; Silicon films; Solar cells; TOPCon
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2021.111544

The potential of passivating contacts incorporating in situ phosphorus (P)-doped polycrystalline silicon (poly-Si) films grown by low pressure chemical vapor deposition (LPCVD) is demonstrated in this work by integrating these layers at the rear side of large-area (241.3 cm2) bifacial n-type Tunnel Oxide Passivated Contact (n-TOPCon) solar cells with diffused front emitter and screen-printed contacts. In situ doped poly-Si films are studied as their use could simplify the production of industrial n-TOPCon solar cells compared to the common approach relying on ex situ doping of intrinsic LPCVD poly-Si films. The developed poly-Si passivating contacts exhibited excellent characteristics with low recombination current densities in passivated and screen-printing metallized regions down to 2.3 fA/cm2 and 65.8 fA/cm2, respectively, and a low contact resistivity of 2.0 mΩ⋅cm2. For reaching the best passivating contact characteristics and high solar cell efficiencies, a poly-Si film thickness of 150–200 nm was found to be optimal while a polished rear surface morphology was found to be beneficial. The best solar cell reached a certified power conversion efficiency of 23.01% along with a high open circuit voltage of 691.7 mV, enabled by the passivating contacts with the in situ doped poly-Si films. 1-cell glass-glass laminates were also fabricated with the developed solar cells, which showed no loss in their power output both upon 400 thermal cycles and after 1000 h of damp heat testing. Lastly, a roadmap is presented, indicating strategies to achieve efficiencies up to 25.5% with n-TOPCon solar cells incorporating the in situ P-doped LPCVD poly-Si films. [Display omitted] •In situ P-doped LPCVD poly-Si passivating contacts integrated in n-TOPCon solar cells.•241.3 cm2-large bifacial n-TOPCon devices with 23.01% certified efficiency demonstrated.•Using ≥ 150 nm of poly-Si and polished rear side improves the solar cell efficiency.•1-cell glass-glass laminates of the devices pass damp heat and thermal cycling tests.•Roadmap to 25.5% efficiency presented.