Fraunhofer ISE-Roman KEDING

Fraunhofer ISE / Photo Guido Kirsch PRECISE SELECTIVE DOPING AND METALLIZATION FOR NEXT-GENERATION PERC TECHNOLOGY R.Keding, R.Efinger, E.Lohmller, M.Jahn, T. Fellmeth, M.Messmer, S.Meier-Meybrunn, J.Horzel, S.Lohmller, 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. Lohmller 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. Lohmller 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. 032422225 Thank you for your Attention Fraunhofer Institute for Solar Energy Systems ISE Dr.-Ing. Roman Keding www.ise.fraunhofer.de roman.kedingise.fraunhofer.de Fotos Fraunhofer ISE