Technologie Evolutives et Disruptives pour les prochaines générations de cellules solaires Silicium

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1 Technologie Evolutives et Disruptives pour les prochaines générations de cellules solaires Silicium M. Despeisse, on behalf of CSEM and EPFL/pvlab research teams pictures 6 cm high at 11 cm vertical Swiss PV days Matthieu DESPEISSE page 1 HIGH PERFORMANCE LOW COST 54 % of PV system cost from BOS incl.inverter 46 % from module MATERIALS, PROCESSES and TECHNOLOGIES For COST-COMPETITIVE MANUFACTURING HIGH FIELD PERFORMANCE Low $/Wp HIGH EFFICIENCY Low $/kwh Swiss PV days Matthieu DESPEISSE page 2 1

2 HIGH PERFORMANCE LOW COST Si-PV: new technologies era PERx SHJ TANDEM IBC Al-BSF Swiss PV days Matthieu DESPEISSE page 3 STEP 1: IMPLEMENTING PASSIVATING CONTACTS & GOING BIFACIAL Direct contact between c-si and metal Recombinative contact Lower operating voltage & V oc Heterocontact between c-si and metal Passivating contacts Higher operating voltage & V oc Bifacial structure Classical c-si diffused solar cells Al BSF PERC AlOx/SiNx Al Swiss PV days Matthieu DESPEISSE page 4 2

3 STEP 1: IMPLEMENTING PASSIVATING CONTACTS & GOING BIFACIAL 5 mm THIN FILM COATING KEY FOR HIGH EFFICIENCY Hetero junction Contact < 250 ⁰C High Temperature Contact 5 µm Swiss PV days Matthieu DESPEISSE page 5 STEP 1: IMPLEMENTING PASSIVATING CONTACTS & GOING BIFACIAL Evolutive Integration of high temperature passivating contacts Industrial p-perc [1] ( mm 2 ) J sc = 40.2 ma/cm 2 ; FF= 80.3 % V oc = mv; η = 22.1% FULL-AREA REAR PASSIVATING CONTACT: no tradeoff VOC/FF, no patterning, reduced recombination ITO SiC x (n) Chem-SiO x SiC x (p) ITO Ag Ag n+ buried junction c-si(p) p+ buried junction BOTH SIDES PASSIVATING CONTACT: reduced recombination losses, higher perf. Swiss PV days Matthieu DESPEISSE page 6 3

4 T [ C] h (%) J sc (ma/cm h (%) 2 ) J sc (ma/cm 2 ) h (%) T [ C] J sc (ma/cm 2 ) V oc (mv) STEP 1: IMPLEMENTING PASSIVATING CONTACTS & GOING BIFACIAL 730 (a) 730 (b) (a) high operating voltages FF up to 84 %, V OC of 727 mv on flat wafers : 33.8 high 700 passivation, low transport losses 700 achieved. SiOx/SiCx high temperature passivating contacts developed in EPFL/CSEM: 690 V oc (mv) (b) Target: achieve similar properties on textured surfaces + limit front-side parasitic absorption V FF oc (mv) (%) FF (%) (a) (c) 85 (b) (d) (c) 45 (d) FF = 84 % V OC = 727 mv V oc = 705 mv J sc = 39.2 ma/cm C 850 C FF = 81.7 % 875 C 875 C 10 h = 22.6 % (c) (d) CH4 flow ratio a.uch 4 /SiH 4 Ratio CH4 flow ratio a.u CH 20 4 /SiH 4 Ratio Voltage (V) 850 C FF (%) Curent Density (ma/cm 2 ) See poster of Josua Stuckelberger - EPFL Swiss PV days Matthieu DESPEISSE page 7 STEP 1: IMPLEMENTING PASSIVATING CONTACTS & GOING BIFACIAL TOWARDS LEAN PROCESS FLOW INTEGRATION of HIGH TEMPERATURE PASSIVATING CONTACTS Approach 1: Co-annealing with POCl 3 process for emitter formation Approach 2: Co-firing with front side Ag-paste As deposited io x (p) Annealed 900 C; 15 min µc-sio x (p) SiO x 800 Example of a T-profile (POCl 3 -diffusion) Time [min] nc-sic x (p) Chem-SiO x H-atoms C-atoms c-si(p) s Example of a T-profile (firing) 60 See poster of Josua Stuckelberger - EPFL Swiss PV days Matthieu DESPEISSE page 8 4

5 DISRUPTIVE APPROACH : SILICON HETEROJUNCTION LEAN PROCESS FLOW, HIGH PASSIVATION Chemical baths c-si surface preparation PECVD a-si:h thin films deposition, intrinsic and doped: i-n, i-p PVD TCO Metallization Screen printing + curing at 200 C Silicon HETEROJUNCTION Cells and Modules R&D platforms established at CSEM Swiss PV days Matthieu DESPEISSE page 9 Best cell produced so far in CSEM: 24.1 % V OC = 727 mv, J SC = 40.8 ma/cm2, FF = 81.1 % Processes for a-si:h deposition key to achieve required opto-electronic properties. Electron-selective passivating contact Metal TCO (doped) a-si:h i1 i2 i3 TCO (n) a-si:h (i) a-si:h (i) a-si:h c-si 5 nm Swiss PV days Matthieu DESPEISSE page 10 5

6 HIGH EFFICIENCY in PILOT PRODUCTION Swiss PV days Matthieu DESPEISSE page 11 Alternative PECVD reactor : MIRROR Concept: Both-sides deposition without vacuum break/no flipping of wafer Cross contamination management: i/n in 1 reactor, i/p in 1 reactor Parallelism no no compensation compensation proper proper compensation compensation Swiss PV days Matthieu DESPEISSE page 12 6

7 SMARTWIRE TECHNOLOGY BENEFITS Less shading Less resistivity losses Cell paste usage (up to 70%) Better resistance for micro cracks Low temperature and low thermal stress interconnection technology No alignment needed ( MBB) Aesthetically attractive Front 25 mg BBless Front 125 mg 5BB Ag cost = 1.3 $cent/cell Ag cost = 6.8 $cent/cell Swiss PV days Matthieu DESPEISSE page 13 NEW GENERATION SMARTWIRE Cost decrease in wires : Indium-free low temperature alloy coating on wires Performance increase : + 2% from new design & UV-through Demonstration of metallurgical bonding btw. HJT cell finger and a wire w. selected Indium free low T solder satisfying above criteria. Cell metallization Low T solder coating wire Ag paste on wire after detachment: AgX2 phase IEC 61215:2016 X1 X2 and IEC 61739:2016 Ag After pastewire on wire detachment, after detachment: Ag AgX2 paste phase on wire, Ag3Sn phase. After wire detachment paste removed on finger + AgX2 phase Reliability AgX2 (PERC): After wiredetachment, after detachment paste paste removed, on Ag3Sn finger + phase. AgX2 phase Coating w. Ag diffusion COPPER WIRE Ag paste w. In diffusion High temperature Ag paste Reliability (HJT): Si wafer PTC < 1% degradation after 3xIEC X2 DH < 2% degradation after 3xIEC PTC < 1% degradation after 3xIEC DH < 3% degradation after 2xIEC Crack within coating, w. Ag3Sn phase BiSn coating Swiss PV days Matthieu DESPEISSE page 14 7

8 Efficiency p-type wafer 180µm: ~ 62 $cts/wafer n-type wafer 180µm: ~ 68 $cts/wafer Cost decrease w. thickness: 1.5 $cts/10 µm n-type wafer 120µm: ~ 59 $cts/wafer Δη median ± 0% Thin wafer integration in production: potential for down to 120 µm as-cut nstrated by Meyer Burger. - Excellent surface passivation permits no performance loss (J SC loss, V OC gain). - Bifacial structure equilibrates stress on both cell sides. As-cut wafer thickness Swiss PV days Matthieu DESPEISSE page 15 2 : BACK CONTACTS w. PASSIVATING CONTACTS BACK CONTACT Challenge for cost-effective manufacturing keeping high efficiency. ion solar cell Heteroju Front-side current loss: Parasitic absorption high(est) efficiencies complex processing Highest efficiency potential nstrated: world record Kaneka / 26.6 % [K. Yoshikawa, Nature Energy 2, (2017)] «TUNNEL IBC-HJT» concept Swiss PV days Matthieu DESPEISSE page 16 8

9 2 : BACK CONTACTS w. PASSIVATING CONTACTS SIMPLE PROCESS FLOW MINIMIZATION OF MATERIALS HIGH EFFICIENCY nstrated so far up to 24.1 % Transfer to full wafer industrial processing. Swiss PV days Matthieu DESPEISSE page 17 EFFICIENCY DRIVEN TECHNOLOGY UPGRADE Silicon based PV devices IBC-HETEROJUNCTION - HETEROJONCTION: Record 25.6 : 26.6 %% IBC: 26 % % 25 % 24 % 23 % 22 % 21 % TANDEM Theoretical limit c-si single cell: 29.4 % Cell 1 High Eg Cell 2 Low Eg % 19 % 20 % mc: % Record 21.2 % CZ PERC: % Record 22.1 % HETEROJONCTION: % Record % PASSIVATING CONTACTS Record : 25.8 % - ++ Swiss PV days Matthieu DESPEISSE page 18 9

10 3 : SILICON BASED TANDEM CELLS PEROVSKITE/Si III-V/Si World records: 32.8 % 4-terminal tandem III-V on Silicon HJT % 4-terminal triple junction III-V on Silicon HJT Breakthrough in III-V manufacturing with drastic costs New Integration approach Alternative top cell material w. low cost potential > 25 % certified efficiency for monolithic PK/Si tandem achieved at EPFL/CSEM See poster of Quentin Jeangros - EPFL Swiss PV days Matthieu DESPEISSE page 19 CONCLUSION PERC PASSIVATING CONTACTS to extend cell efficiency > 24 %: High temperature approaches w. SiOx/SiCx developed at CSEM/EPFL. High electrical properties. Lean process flow to nstrate. Silicon Heterojunction w. > 24 % at CSEM. Simple process flow, s, bifacial, lowest LCOE. Advanced manufacturing developed w. Swiss industry. Passiv. contacts BACK CONTACTS to extend cell efficiency > %: Simple process flow «TUNNEL-IBC» developed at CSEM/EPFL. In transfer to Swiss industry. IBC Perovskite as add-on technology to Silicon for > 27 % > 25 % nstrated by EPFL/CSEM. Work on higher eff., reliability, industrial processes. TANDEM Swiss PV days Matthieu DESPEISSE page 20 10

11 Thank you to all colleagues & partners Swiss PV days Matthieu DESPEISSE page 21 CSEM PV Facade HJT cells «Solar Visualised in Europe Award» Thank you for your attention SmartWire Heterojunction PV facade CSEM Swiss PV days Matthieu DESPEISSE page 22 11