Dry Passivation Process for Silicon Heterojunction Solar Cells Using Hydrogen Plasma Treatment Followed by In Situ a-Si:H Deposition

• Published in: IEEE journal of photovoltaics Vol. 8; no. 6; pp. 1539 - 1545
• Main Authors: Xu, Menglei, Wang, Chong, Bearda, Twan, Simoen, Eddy, Radhakrishnan, Hariharsudan Sivaramakrishnan, Gordon, Ivan, Li, Wei, Szlufcik, Jozef, Poortmans, Jef
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01-11-2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amorphous materials; Amorphous silicon; Annealing; Carrier lifetime; Deep level transient spectroscopy; Deposition; Flow velocity; Gas flow; Heterojunctions; hydrogen (H<named-content xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" content-type="math" xlink:type="simple"> <inline-formula> <tex-math notation="LaTeX"> _{2}</tex-math> </inline-formula> </named-content>) plasma; Hydrogen plasma; Hydrogen storage; Hydrogenated amorphous silicon (a-Si:H); Minority carriers; Passivation; Passivity; Photovoltaic cells; Plasma; Plasma processing; Scanning electron microscopy; Scanning transmission electron microscopy; Silicon; silicon heterojunction (SHJ) solar cells; Silicon substrates; Solar cells; Transmission electron microscopy
• ISSN: 2156-3381; 2156-3403
• DOI: 10.1109/JPHOTOV.2018.2871329

A fully dry and hydrofluoric-free low-temperature process has been developed to passivate n-type crystalline silicon (c-Si) surfaces. Particularly, the use of a hydrogen (H 2 ) plasma treatment followed by in situ intrinsic hydrogenated amorphous silicon (a-Si:H) deposition has been investigated. The impact of H 2 gas flow rate and H 2 plasma processing time on the a-Si:H/c-Si interface passivation quality is studied. Optimal H 2 plasma processing conditions result in the best effective minority carrier lifetime of up to 2.5 ms at an injection level of 1 × 10 15 cm −3 , equivalent to the best effective surface recombination velocity of 4 cm/s. The reasons that enable such superior passivation quality are discussed in this paper based on the characterization of the a-Si:H/c-Si interface and c-Si substrate using transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy, and deep-level transient spectroscopy.