Fraunhofer ISE-Roman KEDING
© Fraunhofer ISE / Photo: Guido Kirsch PRECISE SELECTIVE DOPING AND METALLIZATION FOR NEXT-GENERATION PERC TECHNOLOGY R.Keding, R.Efinger, E.Lohmüller, M.Jahn, T. Fellmeth, M.Messmer, S.Meier-Meybrunn, J.Horzel, S.Lohmüller, J.Weber, M.Demant, A.Lorenz, P.Saint- Cast, A.A.Brand, J.Nekarda, F.Clement, J.Greulich, R.Preu, M.Pickrell 1 , J.Hermans 2 1 Sun Chemical (UK) 2 Meyer Burger (NL) B.V.2 AGENDA Motivation PERC‘s roadmap according to ISE ITRPV predictions Approach PERC base line Precise, congruent patterning Application Selective emitter PERC Bifacial cells Conclusions ITRPV: International Technology Roadmap for Photovoltaic3 Motivation PERC‘s roadmap according to ISE 7-step program to 240 W/m 2 * 1: Fine, high aspect ratio front contacts 2: No-overlap selective emitters 3: Low-cost, high quality material 4: Increased productivity 5: Bifaciality 6: Bifacial shingled cells with passivated edge 7: Introduction of passivated contacts R. Preu et at., SNEC 2018 *Bifacial illumination: G front = 1000 W/m 2 , G rear = 100 W/m 24 Motivation ITRPV predictions for 2029 Feature size target x met below 20 μm Effective dark saturation current density target per side J 0,eff below 40 fA/cm 2 Precision enables ITRPV predictions Max. alignment tolerance of ±15 μm x pitch ( μm) J 0,eff (fA/cm 2 ) x dop = 140 μm, x met = 40 μm x dop = x met = 20 μm D Aspect ratio = 0.62 ITRPV, 2018 Results, Tenth Edition, March 2019 x pitch x dop x met x dop = 70 μm, x met = 40 μm Typical finger distance 29 μm 18 μm5 Bifacial cells enable Collection of light from both solar cell sides Additional yield by 10 - 40% [1-3] Bifacial cells will gain market share 15% in 2019 60% in 2029 Even more patterning Monofacial Bifacial Motivation ITRPV predictions for 2029 [1] L. Podlowski et al., Bifi workshop, 2017; [2] N. Eisenberg, R. Kopecek, V. Fakhfouri et al., PV-tech.org, 2017; [3] A. Flores et al., Taiyang News, 2017;6 Industrial PERC solar cells processed in two separate pilot- lines Front-End (no metal) Back-End Efficiency of 21.6 % Evaluation of Machines and Components Materials like solar cell precursors Approach PERC base line process7 Digital file generation based on e.g. screen-printed pattern Procedure Fabrication of test samples Imaging, r x,y = 5 μm Shape determination Offset determination Typ. max. offset ± 50 μm Shape-congruent file generation incl. Offset (algorithm) Vision: AOI meets file generation Approach Precise, congruent patterning Initial Corrected Imaging File generation AOI: Automated Optical Inspection8 R inkjet for ink Patterning process 2 and 1 can be adapted to each other Patterning process 1 can be adapted to process 2 and the processes are directly in a row Potential industrial PERC upgrades Approach Industrial application LDSE: Laser-diffused sel. Emitter; LCO: Laser contact opening; SP: Screen printing; SE: Selective emitter; Laser LCO Laser LDSE Front-End SP metal Laser LCO SP metal Laser PassDop Patterning 1 Patterning 2 Back-End Cell SE PERC / Plating biPERC biPERL9 Screen-printed metal on ink Conversion efficiencies measured on a black chuck;20 Bifacial PERC Patterning LCO patterning Laser processing Metal application Screen printing Al Paste (not firing-through) Contact fomation Fast Firing Al-Si alloying External Precursor Front-End processing p-type Cz-Si biPERC File generator Laser Contact Opening AOI Rear screen printing AOI Front screen printing Fast Firing MC 11001111 SiN x c-Si (n ++ ) metal metal Al 2 O 3 /SiON x c-Si (p) c-Si (p ++ )21 Solar cell results [1] E. Lohmüller et al., WCPEC, 2018; [2] T. Fellmeth et al., PV-SEC, 2017; Generally: method works stable on e.g. 100 μm Al on 30 μm LCO Type Prec. V OC (mV) J SC (mA/cm 2 ) FF (%) front (%) rear (%) (%) p out * (mW/cm 2 ) monoPERC ISE 667 40.2 80.7 21.6 21.6 biPERL [1] ISE 651 39.2 79.9 20.4 18.0 88 22.2 biPERC [2] Yes 674 39.7 80.0 21.4 12.6 59 22.7 * p out forG front = 100 mW/cm 2 (STC) and G rear = 10 mW/cm 2 ; Conversion efficiencies measured on a black chuck;22 Solar cell results [1] E. Lohmüller et al., WCPEC, 2018; [2] T. Fellmeth et al., PV-SEC, 2017; Generally: method works stable on e.g. 100 μm Al on 30 μm LCO Type Prec. V OC (mV) J SC (mA/cm 2 ) FF (%) front (%) rear (%) (%) p out * (mW/cm 2 ) monoPERC ISE 667 40.2 80.7 21.6 21.6 biPERL [1] ISE 651 39.2 79.9 20.4 18.0 88 24.0 biPERC [2] Yes 674 39.7 80.0 21.4 12.6 59 23.9 * p out forG front = 100 mW/cm 2 (STC) and G rear = 20 mW/cm 2 ; Conversion efficiencies measured on a black chuck;23 Conclusion Digital method established for precise, shape-congruent patterning Scalable with AOI High alignment accuracy of ±15 μm between different patterning methods Successful process integration biPERL (p-type) biPERC (p-type) Initial Corrected Ink - SP Laser - SP24 Acknowledgement The authors would like to thank all colleagues at Fraunhofer ISE The German Federal Ministry for Economic Affairs and Energy for funding within the projects “HELENE” (contract no. 0325777D) “PV-BAT400” (contract no. 0324145) SOLAR-ERA.NET for funding within the project PEarl (contract no. 0324222)25 Thank you for your Attention! Fraunhofer Institute for Solar Energy Systems ISE Dr.-Ing. Roman Keding www.ise.fraunhofer.de roman.keding@ise.fraunhofer.de Fotos © Fraunhofer ISE
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