Ex-situ phosphorus-doped polycrystalline silicon passivating contacts for high-efficiency solar cells by physical vapour deposition. (1st May 2023)

• Record Type: Journal Article
• Authors: Truong, Thien; Kang, Di; Wang, Er-Chien; Wang, Jiali; Phang, Sieu Pheng; Macdonald, Daniel; Stuckelberger, Josua
• Is Part Of: Solar energy. Volume 255(2023)
• Page Start: 285
• Page End: 291
• Publication Date: 2023-05-01
• Subjects: Physical vapor deposition -- Poly-Si -- Passivating contacts -- Sputtering -- Ex-situ diffusion; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2023.03.048
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Optimisation for poly-Si passivating contacts prepared by sputtering and ex-situ diffusion. The difference in performance between POCl3 diffusion and spin-on doping is due tocrystallinity and diffusion mechanism. With POCl3 diffusion: an i Voc of ∼720 mV, a J 0 of 2.6 fA/cm 2 after a hydrogenation, and a contact resistivity ρ c of less than 10 mΩ.cm 2 were achieved. Quokka3 simulations show that cell efficiencies as high as 25% are possible using the optimised passivating contacts. Abstract: We present ex-situ phosphorus-doped polycrystalline silicon (poly-Si) passivating contacts fabricated by the physical vapour deposition method, specifically sputtering. This technique is currently of great interest to the photovoltaics (PV) community due to its low deposition temperature, small footprint, high throughput, and use of low-hazard, solid targets and gases. We optimise the performance of the passivating contacts by adjusting various parameters from the sputtering of amorphous Si films to the formation of the poly-Si layers by a high-temperature thermal diffusion (with phosphorus oxychloride – POCl3, or phosphorus spin-on glass as the dopant sources). For the case of POCl3 diffusion, a high iV oc of ∼720 mV together with a low J 0 of 2.6 fA/cm 2 after a hydrogenation treatment by atomic layer deposition (ALD) AlOx and forming gas annealing (FGA), and a low contact resistivity ρc of less than 10 mΩ cm 2 were achieved. Meanwhile, with spin-on doping, a low average iV oc of ∼600 mV was observed. This variation in performance could be explained by the difference in the crystallinity and the diffusion mechanism of the sputtered Si films after different subsequent thermal diffusion processes. Quokka3 simulations show that cell efficiencies as high as 25% are possible using the optimised passivating contacts. The results demonstrate the potential of these PVD poly-Si films as a promising candidate for future industrial solar cells.