MANZ AG Industrial PECVD Al2O3/SiNx Rear-Passivation and Flat-Top nanosecond laser contact opening for 20.5 % efficient Si PERC solar cells Dr. Florian Schwarz1, Dr. Rafel Ferré1, Christopher Jahn1, Dr. Tobias Baier1, Birgit Beier2, Dr. Thorsten Dullweber2, Dr. Sebastian Gatz1 1) Manz AG, Steigaeckerstrasse 5, 72768 Reutlingen, Germany 2) Institute for Solar Energy Research Hamelin (ISFH), Am Ohrberg 1, 31860 Emmerthal, Germany Expected market share of different c-Si cell concepts ITRPV 2014 International Technology Roadmap for Photovoltaic, Edition 2014, retrieved May 14, 2014, from http:// www.itrpv.net l Rear-side passivated PERC solar cells will gain significant market share à 20 %+ in 2016 à 50 % in 2024 l Conversion of existing Al-BSF cell production in PERC cell production reasonable Strictly Confidential 10/4/14 2 Additional process steps for conversion from Al-BSF to PERC Process equipment (handling not included) Process steps for Al-BSF cells on mono and multi Additional process steps required for PERC approach (SDR +) Texturing Phosphorus diffusion PSG etch + Chemical Edge Isolation Front PECVD-SiNx screen printing Rear polish Rear dielectric e.g. Al2O3/SiNx Rear structuring e.g. LCO Co-firing Al-BSF cell PERC cell Strictly Confidential 10/4/14 3 Additional process steps for conversion from Al-BSF to PERC Process equipment (handling not included) Process steps for Al-BSF cells on mono and multi Additional process steps required for PERC approach (SDR +) Texturing Phosphorus diffusion PSG etch + Chemical Edge Isolation Front PECVD-SiNx screen printing Rear polish Rear dielectric e.g. Al2O3/SiNx VCS 1200 Vertical Coating System Rear structuring e.g. LCO LAS 2400 Laser Ablation System Manz provides equipment and processing technology to convert standard cell production into PERC production Co-firing Al-BSF cell IPSG CEI POL 4800 single tool IPOL 4800 add on existing tool PERC cell Strictly Confidential 10/4/14 4 Agenda l VCS 1200, Vertical Coating System à Surface passivation quality on test structures à Multi-PERC solar cell results l LAS 2400, Laser Ablation System à Single spot designs à Mono-PERC solar cell results l Characterisation of up to 20.5% efficient Mono-PERC solar cells applying VCS 1200 and LAS 2400 processes Strictly Confidential 10/4/14 5 Vertical Coating System – VCS 1200 setup 1. 2. 3. 4. 5. 6. 7. 8. Carrier loading / unloading Vertical carrier exchange station Carrier handling Load-lock Heating station PECVD station Vacuum system (pumps) Service & cleaning drawer 8 1 5 3 4 2 6 7 Strictly Confidential 10/4/14 6 Vertical Coating System VCS 1200 System features and Plasma technology PECVD System features l l l l l Front and back side coating (e.g. SiNx, Al2O3/SiNx) Fully automated è Cassette to Cassette handling Gross throughput 1200 wph Small footprint Modular design enables clustering of tools à Ideal throughput matching à Customer-friendly scalability à Easy maintenance & handling (1 operator only) à Easy to integrate into new and existing lines Innovative High Power Plasma technology carrier (electrostatic) Si-wafer l ~ l l l l l l Al2O3/SiNx coating in one step à yield boost and quality gain Wafer not electrically contacted High density plasma à best gas utilization (> 90%) Very high deposition rates Excellent film quality High uniformity Optimum reproducibility Strictly Confidential 10/4/14 7 Vertical Coating System VCS 1200 Electrostatic Carrier Features à Thin wafer handling à Minimized wrap around • Full area clamping • No force on edges • Low breakage rate VCS1200 à Pin mark free with best uniformity t n Al2O3 5.7% 0.6% SiNx 2.7% 0.5% à Particle avoidance • due to vertical position • No mechanical constraints p-2-p inline PECVD Strictly Confidential 10/4/14 8 VCS 1200 Surface passivation performance on different substrates Lifetime results PL-Mappings of Cz-coated lifetime samples (ISE) as depo 63 µs FZ 2 Ohm*cm 250 µm CZ 2 Ohm*cm 180 µm fired 353 µs Optimum Al2O3-thicknesses • Monocrystalline Silicon: • Alkaline-textured: 15 nm • Polished: 10 nm • Multicrystalline Silicon: • Iso-textured: 20 nm • Polished: 10 nm Strictly Confidential 10/4/14 9 ISE-reference VCS 1200 recipe 1 VCS 1200 recipe 2 IQE [%], Reflectance [%] VCS 1200 Surface passivation compared to inline passivation PERC solar cell results ISE-reference VCS 1200 recipe 1 VCS 1200 recipe 2 l Outperforming reference passivation, esp. l No major IQE-/Reflectance - differences on non-polished surfaces (∆ Voc,avg. = 6 mV) detected for LFC-PERC cells applying l Best multi LFC-PERC cell: different rear passivation stacks à η = 18.5 % l Excellent rear side passivation quality à Voc = 641 mV l Identical internal rear reflectance à Jsc = 36.6 mA/cm² 10 10/4/14 à FF = 78.7 % Strictly Confidential Agenda l VCS 1200, Vertical Coating System à Surface passivation quality on test structures à Multi-PERC solar cell results l LAS 2400, Laser Ablation System à Single spot designs à Mono-PERC solar cell results l Characterisation of up to 20.5% efficient Mono-PERC solar cells applying VCS 1200 and LAS 2400 processes Strictly Confidential 10/4/14 11 LAS 2400, Laser Ablation System System features l l l l l Fully automated Laser system Laser ablation for LCO rear contact Gross throughput 2400 wph à Integration with Manz VCS1200 possible à Intelligent production cluster Easy to integrate into new and existing cell factories Single beam scanning à Lines, dotted lines, dots possible à Wide range of ablation widths (20 – 120 µm) Strictly Confidential 10/4/14 12 LAS 2400, Laser Ablation System Flat-top nanoseconds laser opening ps ns ns + optics intensity melting! ablation warming ~ 80 µm spot size / space coordinate Strictly Confidential 10/4/14 13 LAS 2400, Laser Ablation System Flat-top nanoseconds laser opening l Flat-Top energy distribution with rectangular spot shape à high edge steepness à broad plateau compared to Gaussian profile Y à no demand for an additional (chemical) step l In-house developed optics à Continuously variable spot width from 20-120 µm à Less sensitive to focal plan positioning compared to Gaussian à Possible aspect ratios 1:1, 1:2, 1:3 resulting in increased throughput Optical simulation (Zemax) Experimentally measured energy distribution Strictly Confidential X Ablation pattern detected by light microscopy 10/4/14 14 LAS 2400, Laser Ablation System Single spot design 30µm x 30µm 30µm x 90µm Measured energy distribution (top view) Horizontal axis Vertical axis Optical simulation (Zemax) 50µm x 50µm 50µm x 150µm Horizontal axis Vertical axis Various contact geometries possible • Lines, dotted lines, dots • Wide range of contact widths (20 -120 µm) Strictly Confidential 10/4/14 15 Agenda l VCS 1200, Vertical Coating System à Surface passivation quality on test structures à Multi-PERC solar cell results l LAS 2400, Laser Ablation System à Single spot designs à Mono-PERC solar cell results l Characterisation of up to 20.5% efficient Mono-PERC solar cells applying VCS 1200 and LAS 2400 processes Strictly Confidential 10/4/14 16 PERC solar cell: best cell results monocrystalline, Cz-silicon 156x156 mm² ISFH reference* Manz LCO Electroluminescense images Front end Front end RS: ALD-AlOx RS: ALD-AlOx RS: inline SiNx RS: inline SiNx Inline ARC SiNx Inline ARC SiNx laboratory-type LCO (ps) Manz LAS 2400 Back end Back end η = 20.56 % Voc = 658 mV Jsc = 38.9 mA/cm² FF = 80.3% ISFH reference Manz LCO η = 20.52 % Voc = 656 mV Jsc = 38.9 mA/cm² FF = 80.3% l Manz LAS 2400 MP tool performs very similar compared to laboratory-type ps laser ablation tool * T. Dullweber et al., Prog. Photovolt. 20 (2012) 630 Strictly Confidential 10/4/14 17 Experimental design and best cell results monocrystalline, Cz-silicon 156x156 mm² ISFH reference* Manz LCO Front end Front end RS: ALD-AlOx RS: ALD-AlOx RS: inline SiNx RS: inline SiNx Inline ARC SiNx Manz passivation Manz pass. + LCO Front end Front end RS: MANZ VCS 1200 RS: MANZ VCS 1200 Inline ARC SiNx Inline ARC SiNx Inline ARC SiNx laboratory-type LCO (ps) Manz LAS 2400 laboratory-type LCO (ps) Manz LAS 2400 Back end Back end Back end Back end η = 20.32 % Voc = 655 mV Jsc = 38.8 mA/cm² FF = 80.0% η = 20.31 % Voc = 656 mV Jsc = 38.9 mA/cm² FF = 79.6% η = 20.56 % Voc = 658 mV Jsc = 38.9 mA/cm² FF = 80.3% η = 20.52 % Voc = 656 mV Jsc = 38.9 mA/cm² FF = 80.3% l Manz VCS 1200 shows similar performance compared to ALD-AlOx / inline SiNx stacks à Slightly lower η due to increased series resistance and/or lower Voc à Fine-tuning of Laser adjustment needed or adjustment of hydrogenation with ISFH firing profile * T. Dullweber et al., Prog. Photovolt. 20 (2012) 630 Strictly Confidential 10/4/14 18 Monocrystalline PERC solar cells IQE and Reflectance IQE / Reflectance 1.0 Srear (from fit) 0.9 IQE / Reflectance [-] 0.8 0.7 ISFH Reference Zelle 13 ISFH reference ~ 40 cm/s Manz LCO ~ 95 cm/s Manz Passivation Zelle 22 0.6 Manz passivation ~ 66 cm/s 0.5 Manz LCO + LCO ~ 59 cm/s Manz pass. 0.4 Zelle 23 0.3 0.2 Manz Pass. + LCO Zelle 12 0.1 0.0 300 400 500 600 700 800 900 1000 1100 1200 Wavelength [nm] l Very similar effective rear surface recombination velocities Srear and rear reflectance l No major differences between appliedStrictly rearConfidential side passivation and laser ablation system 10/4/14 19 Conclusions VCS 1200 Al2O3/SiNx coating shows very good rear side passivation quality on mono and multi w/o high requirements regarding polish Best multi-Si PERC solar cells in cell-run with Fraunhofer ISE: 18.5% Manz LAS 2400 features excellent dielectric ablation on mono and multi at high throughput IQE / Reflectance 1.0 0.9 ISFH Reference Zelle 13 IQE / Reflectance [-] 0.8 0.7 Manz Passivation Zelle 22 0.6 0.5 0.4 Manz LCO Zelle 23 0.3 0.2 Manz Pass. + LCO Zelle 12 0.1 0.0 300 400 500 600 700 800 Samplings with several mono and multi manufacturers applying VCS 1200 and LAS 2400 processes result in solar cell efficiencies up to 20.5 % 900 1000 1100 1200 Wavelength [nm] Manz provides equipment and processing technology to convert standard cell production into PERC production Manz became 2014 the winner of the award for PERC Production Solutions within the category Silicon Innovation Award Strictly Confidential 10/4/14 20 Thank you.... 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