MULTI-WIRE INTERCONNECTION OF BACK-CONTACTED SILICON HETEROJUNCTION SOLAR CELLS

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MULTI-WIRE INTERCONNECTION OF BACK-CONTACTED SILICON HETEROJUNCTION SOLAR CELLS A. Faes 1, B. Paviet-Salomon 1, A. Tomasi 2, D. Lachenal 3, N. Badel 1, G. Christmann 1, L. Barraud 1, A.

1 MULTI-WIRE INTERCONNECTION OF BACK-CONTACTED SILICON HETEROJUNCTION SOLAR CELLS A. Faes 1, B. Paviet-Salomon 1, A. Tomasi 2, D. Lachenal 3, N. Badel 1, G. Christmann 1, L. Barraud 1, A. Descœudres 1, J. Geissbühler 1, A. Lachowicz 1, J. Chamliaud 1, L. Curvat 1, J. Levrat 1, Q. Jeangros 2, S. Nicolay 1, P. Paet 3, B. Strahm 3, Y. Yao 4, T. Söderström 4, S. De Wolf 5, M. Deseisse 1, and C. Ballif 1 1 CSEM PV-Center, Neuchâtel, Switzerland 2 EPFL, IMT, PV-Lab, Neuchâtel, Switzerland 3 Meyer Burger Research SA, Hauterive, Switzerland 4 Meyer Burger AG, Thun, Switzerland 5 KAUST, Thuwal, Saudi Arabia 7th Worksho on Metallization & Interconnection for Crystalline Silicon Solar Cells October 22-23, 2017 Konstanz

Motivation: why to go for IBC cells and modules?

7 Panasonic (JP) 2014 25.6 SunPower (US) 2016 25.

4 (a) Panasonic (JP) 2016 23.8 (da) SunPower (US) 2016 22.

2 Motivation: why to go for IBC cells and modules? Record back contacted solar cells : Affiliation Year Eff. (%) Kaneka (JP) Panasonic (JP) SunPower (US) Record modules made of back contacted solar cells : Affiliation Year Eff. (%) Kaneka (JP) (a) Panasonic (JP) (da) SunPower (US) (da) - High(est) efficiencies - Aesthetic - Comlex rocessing - High cost Solutions 1. Tunnel-IBC concet: simlified IBC- SHJ device 2. Multi-wire interconnection to reduce the cost and imrove energy yield Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 1

3 Power Losses Fine line Screenrinting or secial metallization Screen-rinting Electrolating Shadowing for Front contacted cells Screen-rint IBC SmartWire IBC 5BB 3BB Goal = design related 15 6 IBC Save on material + cost & gain in bifaciality [J. Geissbüher et al., Metallization techniques and interconnection schemes for high efficiency silicon heterojunction PV, Coyright PV Int CSEM (2017)] Multi-Wire Interconnection of BC-SHJ Solar Cells Page 2

alignment The tunnel-ibc architecture & rocess flow Tunnel-IBC: IBC-SHJ device with blanket h + collector and tunneling e - contacts 1. Textured c-si 2. Passivating films and ARC 3.

4 alignment The tunnel-ibc architecture & rocess flow Tunnel-IBC: IBC-SHJ device with blanket h + collector and tunneling e - contacts 1. Textured c-si 2. Passivating films and ARC 3. Patterned electron collector 4. Blanket hole collector 1 st atterning: e - fingers 5. TCO/metal electrodes atterning Simlified rocessing: No h + collector atterning Self-aligned e - /h + fingers Only 2 atterning and 1 alignment stes 2 nd atterning: TCO/metal (inkjet) Can we make it even simler? Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 3

Ag and not under-etch the TCO Solutions Use secial screen-rinted Ag aste Thick conductive deosit

5 Backside metallization Suttered Ag metallization High Ag thickness (8-10 µm in case of 5 x 5 cm 2 cell) to kee low series resistance Masking with hotmelt + etching Ag and TCO Issue of etching the Ag and not under-etch the TCO Solutions Use secial screen-rinted Ag aste Thick conductive deosit Used as mask for TCO etching Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 4

6 CSEM s chamion tunnel-ibc device to date Combining our best nc-si:h layers into a tunnel-ibc device: u to 23.9 % efficiency FF > 85 % no lateral shunt R series -limited FF: transort losses at the TCO/hole collector interface are the major limitation [B. Paviet-Salomon et al., IBC-SHJ solar cells featuring an interband tunnel junction enabling simlified rocessing, in roc. EUPVSEC Amsterdam (2017)] Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 5

Coer Plating Bulk Cu Metal Fingers To uscale to 6 cells need of Coer

thickness (µm) No stress at 20 A/dm 2 : it corresonds to 4.

deosit Nearly no bending [A. Lachowicz et al.

7 Coer Plating Bulk Cu Metal Fingers To uscale to 6 cells need of Coer lating New develoed Coer solution Fast lating No internal stress Cu thickness (µm) No stress at 20 A/dm 2 : it corresonds to 4.5 µm/min Need about 10 min to obtain 50 µm About 60 µm thick Cu deosit Nearly no bending [A. Lachowicz et al., this 7 th Metallization Worksho] Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 6

8 SmartWire Concet No busbar cells Wire interconnection 10 cells string 60 cells module Cell measurement Grid Touch from PASAN InSn Coated wire T f =120 C Wire Cell Suorting foil + adhesive IBC Cell: PCB Touch Goal: use the same concet for back contacted cells Remove busbar Reduce the loss in the fingers Enable bifaciality Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 7

9 New Generation SmartWire (SWCT) 1. No Indium INDIUM-FREE COATING (Tiger foil) DH (85 C, 85%RH) with less than 3% of ower reduction after 3000h. TC (-40 C to +85 C): less than 0.2% ower degradation er 100 cycles. Module FF (%) Isc (A) Voc (V) Pmax (W) 60 cells TÜV RHEINLAND CERTIFICATION SmartWire with Indium free coating are certified in 60 cells module by TÜV Rheinland following the new standards IEC 61215:2016 and IEC 61739:2016. Pass > 3x IEC 1500TC & 3000h DH With less that 3% degradation in ower Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 8

10 IBC modules using SmartWires (SWCT) tye zones n-tye zones Fine Ag fingers conductive ads insulating ads SmartWires Key ideas: 1. Multi-level cell interconnection 2. Use only one tye of cell rotated by 180 need even wire numbers n n n n n n Rotate 180 Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 9

11 Conductive adhesive (CA) ad rinting Coer wires Contacting ads Solder In-free ads Conductive adhesive (CA) ads Low-Ag CA ads Silver fingers Solder InSn ads Ag CA ads Reliability after DH and TC Cost of Raw coer wire = 1/3 of InSn coated wire Reliability after dam heat and thermocycling = ok with Pads No Pads With Pads InSn coated wire Raw Cu wire * 1 cell module glass-glass Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 10

Bifaciality and Cell to Module losses The measured bifaciality is about 77.5% (22.5% losses) which corresonds to the light absortion losses calculation Calculated values Wire surface (%) 4.

12 Bifaciality and Cell to Module losses The measured bifaciality is about 77.5% (22.5% losses) which corresonds to the light absortion losses calculation Calculated values Wire surface (%) 4.6% Fingers surface (%) 3.7% Pads surface (%) 13.0% Higher reflectivity of the Si 1.2% Measured values ID Ratio Isc Front vs backside % Front vs backside % Frontside Backside Value of Jsc losses 22.6% The Cell-to-Module ower ratio u to 98% on one cell module (module measured with mask around the cell) Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 11

5 µm/min) and low stress: 6 cell demonstrate In-free Smartwire with only 0.

13 Conclusions Tunnel-IBC: simlified IBC-SHJ architecture with tunnel junction to alleviate the rocess comlexity U to 23.9 % IBC-SHJ cell efficiency demonstrated with Tunnel-IBC technology Coer lating with high deosition rate (4.5 µm/min) and low stress: 6 cell demonstrate In-free Smartwire with only 0.2% ower loss er 100 thermo-cycles (ass more than 1500PTC), Certified by TÜV (new IEC 61215:2016 and IEC 61739:2016) IBC-SmartWire connection Cell-to-Module ratio in ower u to 98% for one cell module Bifaciality of 77.5% obtained Coyright 2017 CSEM Multi-Wire Interconnection of BC-SHJ Solar Cells Page 12

14 Thank you for your attention. contact: Acknowledgement This roject has received funding from the Euroean Union s Horizon2020 Programme for research, technological develoment and demonstration under Grant Agreement n o , n o & n o Coyright 2017 CSEM 7th Metallization Worksho 2017 Page 13

Effective Efficiency of Busbarless solar cells

Effective Efficiency of Busbarless solar cells P. Papet 1, J. Levrat 2, N. Bassi 3, Y. Yao 4, A. Waltinger 5, V. Fakhfouri 3, T. Soderstrom 4, B. Strahm 1 1 Meyer Burger Research, Hauterive, Switzerland.