In situ phosphorus-doped polycrystalline silicon films by low pressure chemical vapor deposition for contact passivation of silicon solar cells. (1st January 2022)

• Record Type: Journal Article
• Authors: Fırat, Meriç; Sivaramakrishnan Radhakrishnan, Hariharsudan; Recamán Payo, María; Duerinckx, Filip; Tous, Loic; Poortmans, Jef
• Is Part Of: Solar energy. Volume 231(2022)
• Page Start: 78
• Page End: 87
• Publication Date: 2022-01-01
• Subjects: Passivating contacts -- Solar cells -- Polysilicon -- LPCVD -- In situ doping -- Phosphorus doping; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2021.11.045
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: Active P concentration of 1.3∙10 20 cm −3 achieved in in situ doped LPCVD poly-Si. Thorough electrical and structural characterization of in situ doped films reported. J 0 down to 1.5 fA/cm 2 and ρ c down to 1.8 mΩ∙cm 2 achieved with the developed films. At the rear of solar cells, 0.41 mA/cm 2 J sc loss expected for use of 100 nm poly-Si. Abstract: In situ phosphorus (P)-doped polycrystalline silicon (poly-Si) films by low pressure chemical vapor deposition (LPCVD) were studied in this work for the fabrication of poly-Si passivating contacts. In situ doping was targeted for enabling the full potential of the high-throughput LPCVD technique, as it could allow leaner fabrication of industrial solar cells featuring poly-Si passivating contacts than the more common ex situ doping routes. By careful optimization of the deposition temperature and the flows of the carrier gas (H2 ) and the dopant precursor (PH3 ), high doping in the poly-Si layers was achieved with active P concentrations up to 1.3⋅10 20 cm −3 . While reduction in the deposition rate ( r dep ) and thus in the throughput is a known problem when growing in situ P-doped films by LPCVD, this reduction could be limited, and the resulting r dep was equal to 0.078 nm/s. The developed poly-Si films were characterized both structurally and in terms of their passivation potential in poly-Si contacts. The latter yielded recombination current densities down to 1.5 fA/cm 2 in passivated ( J 0, p ) and 25.6 fA/cm 2 in screen-printing metallized ( J 0, m ) regions on saw-damage removed (SDR) Cz-Si surfaces, accompanied by a contact resistivity ( ρ c, m ) of 4.9 mΩ⋅cm 2 . On textured Cz-Si surfaces, the corresponding values were J 0, p = 3.5 fA/cm 2, J 0, m = 56.7 fA/cm 2, and ρ c, m = 1.8 mΩ⋅cm 2 . Optical impact of the developed poly-Si films was also assessed and a short circuit density loss of 0.41 mA/cm 2 is predicted per each 100 nm of poly-Si applied at the rear side of solar cells.