High-efficiency selective boron emitter formed by wet chemical etch-back for n-type screen-printed Si solar cells

Tao, Yuguo; Madani, Keeya; Cho, Eunhwan; Rounsaville, Brian; Upadhyaya, Vijaykumar; Rohatgi, Ajeet

doi:10.1063/1.4973626

Title: High-efficiency selective boron emitter formed by wet chemical etch-back for n-type screen-printed Si solar cells

Journal Article · Mon Jan 09 00:00:00 EST 2017 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4973626· OSTI ID:1465957

^[1]; Madani, Keeya ^[1]; Cho, Eunhwan ^[1]; Rounsaville, Brian ^[1]; Upadhyaya, Vijaykumar ^[1]; Rohatgi, Ajeet ^[2]

Georgia Inst. of Technology, Atlanta, GA (United States)
Georgia Inst. of Technology, Atlanta, GA (United States); Suniva Inc., Norcross, GA (United States)

Front metal contact induced recombination and resistance are major efficiency limiting factors of large-area screen-printed n-type front junction Si solar cells with homogeneous emitter and tunnel oxide passivated back contact (TOPCON). Here, this paper shows the development of a selective boron emitter (p⁺/p⁺⁺) formed by a screen-printed resist masking and wet chemical etch-back process, which first grows a porous Si layer and subsequently removes it. Various wet-chemical solutions for forming porous Si layer are investigated. An industrial compatible process with sodium nitrite (NaNO₂) catalyst is developed to uniformly etch-back the ~47 Ω/ atmospheric pressure chemical vapor deposited heavily doped boron emitter to ~135 Ω/ by growing a 320 nm porous Si layer within 3 min and subsequently removing it. After etching back, the boron emitter was subjected to a thermal oxidation to lower the surface concentration and the emitter saturation current density J_0e. Various etched-back emitters were evaluated by measuring J_0e on symmetric test structures with atomic layer deposited aluminum oxide (Al₂O₃) passivation. Very low J_0e of 21, 14, and 9 fA/cm² were obtained for the 120, 150, and 180 Ω/ etched-back emitters, respectively. A solar cell with a selective emitter (65/180 Ω/ ) formed by this etch-back technology and with an Al/Ag contact on the front and TOPCON on the back gave an open-circuit voltage (V_oc) of 682.8 mV and efficiency of 21.04% on n-type Czochralski Si wafer. Finally, this demonstrates the potential of this technology for next generation high-efficiency industrial n-type Si solar cells.

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Research Organization:: Georgia Institute of Technology, Atlanta, GA (United States); Suniva, Inc., Norcross, GA (United States)

Sponsoring Organization:: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office

Grant/Contract Number:: EE0006336; EE0006815; EE0007554

OSTI ID:: 1465957

Alternate ID(s):: OSTI ID: 1361726; OSTI ID: 1893848; OSTI ID: 1893911

Journal Information:: Applied Physics Letters, Vol. 110, Issue 2; ISSN 0003-6951

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 39 works

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Title: High-efficiency selective boron emitter formed by wet chemical etch-back for n-type screen-printed Si solar cells

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