Fraunhofer ISE-Maximilian POSPISCHIL

© Fraunhofer ISE ; FHG- SK: INTERNAL CONFIDENTIAL Additional Applications around the PV Back-End DISPENSING: 0,5) → Increased Bifaciality ◼ Al Fire Through (Al-FT) Pastes[1, 2] potentially replacing → LCO (p-PERC) → AgAl (n-PERT) Challenges: ◼ Contact necking required to prevent parasitic etching ◼ Conductivity of Al pastes [1] E. Navarrete Astorga et al., 10th Spanish Conference on Electron Devices (CDE), 2015 [2] T. Fellmeth et al. , 8th Silicon PV 2019 43µm Non Fire Through Al Fire Through Al © Fraunhofer ISE 10 , 2017 All Dispensed Mini Module Dispensed Interconnection ◼ Dispensing of bus line edges during cell production ◼ Dispensing of conductive adhesive between front and rear bus lines for interconnection Dispensed glue at module level between dispensed bus line edges from cell production Application of Ag- coated and structured ribbons © Fraunhofer ISE 11 , 2017 All Dispensed Mini Module Dispensed Interconnection ◼ Dispensing of bus line edges during cell production ◼ Dispensing of conductive adhesive between front and rear bus lines for interconnection Process flow (one cell module): ◼ Four dispensing steps on cell level ◼ Two additional on module level → No screen printing, no laser Results at interconnected level: → All-dispensed interconnected bifacial cell demonstrated FF (%) Vmpp (V) Impp (A) Pmpp (W) 77.5 0.545 8.60 4.68 © Fraunhofer ISE 12 , 2017 Parallel Dispensing Approaching Different Applications in Si PV Paste supply Wafer movementp-PERC, Front Side: Ag Bifacial PERC, Rear Side: Al, Al-FT n- PERT, FS: AgAl, AL-FT FS- Print RS- Print & HJT, low temp. Ag, AgCu BB- Print © Fraunhofer ISE 13 , 2017 Al-FT vs. AgAl Pimping the BiSoN, IV results ◼ Dispensing and screen printing of AgAl pastes ◼ Jsc: Al-FT group with D=60µm contacts ◼ Voc on high level → BSF Nf,D = 100 Nf,SP = 120 Mihailetchi et al. bifiPV workshop, Chambery, 2014 Δ𝑉𝑜𝑐 𝐽𝑠𝑐 = VT Δ𝐽𝑠𝑐𝐽 𝑠𝑐 © Fraunhofer ISE 14 , 2017 Al-FT vs. AgAl Pimping the BiSoN, FF analysis ◼ Dispensing and screen printing of AgAl pastes ◼ Jsc: Al-FT group with D=60µm contacts ◼ Voc on high level → BSF Challenge: ◼ Still low Al-FT line resistivity Nf,D = 100 Nf,SP = 120 FT-Al ≈ 40µcm © Fraunhofer ISE 15 , 2017 Parallel Dispensing Approaching Different Applications in Si PV Paste supply Wafer movementp-PERC, Front Side: Ag Bifacial PERC, Rear Side: Al, Al-FT n- PERT, FS: AgAl, AL-FT FS- Print RS- Print & HJT, low temp. Ag, AgCu BB- Print © Fraunhofer ISE 16 , 2017 HJT: Low Temperature Paste Evaluation Recent Activities and Challenges Motivation for intense activities ◼ Ag reduction and throughput potential ◼ BB-less, bifacial application ◼ Suitable for many future cell concepts ◼ Temperature sensitive pastes ideal for closed system applications Challenges ◼ Die Swell in polymer extrusion: Polymers tend to retain their initial structure after being forced through small openings ◼ ITO with reduced pinning effects ◼ Paste rheology not yet ideal for dispensing Latest contact on ITO, dispensed with D = 35µm opening 48µm © Fraunhofer ISE 17 , 2017 HJT Application: Dispensing Front and Rear Grid Paste evaluation on industrial precursors, IV results ◼ SP groups only to indicate eta potential (5BB) ◼ Still higher efficiency level of Ag pastes compared to AgCu ◼ First paste to be dispensed with D=35µm → SP level reached at lower ΔmAg ΔmAg = 2 x 65mg ΔmAg = 65mg+120mg Lower wf © Fraunhofer ISE 18 , 2017 Parallel Dispensing on Front and Rear Side Summary & Outlook ◼ Results on PERC: max = 21.9% reached ◼ Record contacts with excellent contacting behaviour: wf = 17µm @ hf = 14µm ◼ Rear Side Activities for Bifacial PERC with Al-FT ◼ Necking required to prevent parasitic etching ◼ First all dispensed mini module demonstrated ◼ n-PERT: Challenging AgAl with Al-FT ◼ Voc gap closing, FF requires better conductivity ◼ HJT: Applying low temperature curing pastes ◼ Sucessfull application of Ag and AgCu pastes ◼ Sucessfull manufacturing of all dispensed cell with max = 22.2%, SP level reached 43µm 17µm © Fraunhofer ISE 19 , 2017 Thank you for your attention! We will be back ☺ Fraunhofer-Institute for Solar Energy Systems ISE Dr.-Ing. Maximilian Pospischil www.ise.fraunhofer.de maximilian.pospischil@ise.fraunhofer.de © Fraunhofer ISE 20 , 2017 Pictures to Remember … … dispensed lines: wf = 17µm, hf = 14µm ☺ ◼ Commercial available screen printing paste, dispensed with 20µm nozzle ◼ Stable processing for 45min., solar cells with N=150 fingers, mAg = 45mg → We are not yet at the limit and haven‘t started commercialization yet …