LONGi Silicon - Xie Tian

N-type Mono Wafer for High Efficiency Solar Cell Manufacturing LONGi Silicon Mar. 13, 2019 2 CONTENTS 内容 Low LCOE Requires High Efficiency 1 Challenge and Solution for High Quality N-type Mono Wafer Manufacturing Future Trend for N-type Mono Wafer 2 3 4 High Efficiency Cell Requires High Quality Wafer LONGi Confidential www.longigroup.com Page 3 Downstream Upstream High Efficiency Lower Module Cost Lower BOS Solar PV System The Solar PV module value proposition had been mostly about the lowest production cost High efficiency modules lower BOS costs and improve overall system economics Value Chain Shifting to Higher Efficiency Poly Solar Wafer Cell Module High efficiency --- the most effective approach for low LCOE 1. Low LCOE Requires High Efficiency (HE) Higher efficiency means fewer modules, less mounting hardware, smaller land, etc. www.longigroup.com Page 4 1. Huge P-PERC capacity up to ~100 GW (mainly for mono) ：1) high efficiency, 2) low cost (higher cost performance); 2. A clear increase of effective N-type cell capacity (HJT, N-PERT, and IBC). High Efficiency Solar Cell Capacity Low LCOE Requires HE: Effective Mono Cell Capacity 2018Q4 www.longigroup.com Page 5 ? Reference: Dr. Radovan Kopecek nPV 2018 N-type Shows High Potential How to guarantee the highest cell efficiency? Low LCOE Requires HE Advantage Weight High quality (HQ) mono wafer! www.longigroup.com Page 6 Ref: Progress in Photovoltaics Research 2) Ga and In-doped Cz-Si are stable, but Ga (2 orders of magnitude below) and In (3 orders of magnitude below) have low segregation coefficients (that of B) in Si.  N-type Cz-Si: high MCL, LID free  Cz-Si contains high amount of oxygen, 5E17~1E18 atoms/cm3 Ref: J. Schmidt and K. Bothe, Physical Review B 69, 024107 (2004) www.longigroup.com Page 8 Intrinsic Advantages of N-type Wafer: Non- sensitive to metal contamination  N-type is much less sensitive to metal contamination (Fe, Cr, Co, W, Cu, and Ni) than p-type Si  Interstitial Fe 10 13 (atoms/cm 3 ): N-type Si MCL down from 1100 us to 100us, P-type Si MCL down from 1300 us to 0.8 us  Surface Fe 10 13 (atoms/cm 3 ): N-type Si MCL down to 20us, P-type Si MCL down to 0.5 us Ref: 1. J. Schmidt, K. Bothe, R. Bock. N-type silicon – the better material choice for industrial high efficiency solar cells. 22 nd European Photovoltaic Solar Energy Conference, 3-7 September 2007, Milan, Italy. 2. D. Macdonald and L. J. Geerligs, Applied Physics Letters, vol. 85, no. 18, pp. 4061–4063, 2004. www.longigroup.com Page 9 Intrinsic Advantages of N-type Wafer: Higher Lifetime  N-type MCL is at least 1 order of magnitude higher than that of p-type  N-type has better performance at low light intensities. Ref: 1. P . P. Altermatt, J. Comput Electron (2011) 10:314-330. 2. Denyuan Song et al. Progress in n-type Si solar cell and module technology for high efficiency and low cost, 38 th IEEE Photovoltaic Specialists Conference, Austin, USA 2012. P-Si module N-Si module Module Ref. Eff (%) Intensity/W m -2 www.longigroup.com Page 10 Intrinsic Advantages of N-type Wafer: Higher Lifetime 750 625 500 375 250 125 0 LS L: 20μ s LSL 20 目标 * USL * 样本均值 326.102 样本 N 536 标准差（组内） 135.449 标准差（整体） 152.135 过程数据 CL 下限 * CL 上限 * PPL 0.67 PPU * Ppk 0.67 CL 下限 0.62 CL 上限 0.72 Cpm * CL 下限 * Cp * CL 下限 * CL 上限 * CPL 0.75 CPU * Cpk 0.75 CL 下限 0.70 CL 上限 0.81 Pp * 整体能力 潜在（组内）能力 PPM USL * PPM 合计 0.00 实测性能 PPM USL * PPM 合计 11913.65 预期组内性能 PPM USL * PPM 合计 22107.52 预期整体性能 组内 整体 P type 0.5-1.5ohm·cm Seed-end Lifetime 8750 7500 6250 5000 3750 2500 1250 LS L: 500μ s LSL 500 目标 * USL * 样本均值 3914.85 样本 N 1455 标准差（组内） 1067.36 标准差（整体） 1171.87 过程数据 CL 下限 * CL 上限 * PPL 0.97 PPU * Ppk 0.97 CL 下限 0.93 CL 上限 1.01 Cpm * CL 下限 * Cp * CL 下限 * CL 上限 * CPL 1.07 CPU * Cpk 1.07 CL 下限 1.02 CL 上限 1.11 Pp * 整体能力 潜在（组内）能力 PPM USL * PPM 合计 0.00 实测性能 PPM USL * PPM 合计 688.73 预期组内性能 PPM USL * PPM 合计 1784.09 预期整体性能 组内 整体 N type 0.2-2ohm·cm Seed-end Lifetime Seed end Tail end Slug Slug A B A A A A A A B B B B B B  Seed end of an ingot: n-type MCL is 1 order of magnitude higher than that of p-type! 326us 3914us www.longigroup.com Page 11 700 600 500 400 300 200 100 0 LS L: 20μ s LSL 20 目标 * USL * 样本均值 153.474 样本 N 638 标准差（组内） 80.6049 标准差（整体） 93.4352 过程数据 CL 下限 * CL 上限 * PPL 0.48 PPU * Ppk 0.48 CL 下限 0.44 CL 上限 0.51 Cpm * CL 下限 * Cp * CL 下限 * CL 上限 * CPL 0.55 CPU * Cpk 0.55 CL 下限 0.51 CL 上限 0.59 Pp * 整体能力 潜在（组内）能力 PPM USL * PPM 合计 0.00 实测性能 PPM USL * PPM 合计 48871.03 预期组内性能 PPM USL * PPM 合计 76571.87 预期整体性能 组内 整体 P type 0.5-1.5ohm·cm Tail-end Lifetime 7200 6000 4800 3600 2400 1200 0 LSL ： 500μ s LSL 500 目标 * USL * 样本均值 1499.57 样本 N 1730 标准差（组内） 1168.1 标准差（整体） 1305.46 过程数据 CL 下限 * CL 上限 * PPL 0.26 PPU * Ppk 0.26 CL 下限 0.24 CL 上限 0.27 Cpm * CL 下限 * Cp * CL 下限 * CL 上限 * CPL 0.29 CPU * Cpk 0.29 CL 下限 0.27 CL 上限 0.30 Pp * 整体能力 潜在（组内）能力 PPM USL * PPM 合计 276300.58 实测性能 PPM USL * PPM 合计 196075.11 预期组内性能 PPM USL * PPM 合计 221931.01 预期整体性能 组内 整体 N Type 0.2-2 ohm·cm Tail-end Lifetime Intrinsic Advantages of N-type Wafer: Higher Lifetime Seed end Tail end Slug Slug A B A A A A A A B B B B B B 153us 1499us  Tail end of an ingot: n-type MCL is 1 order of magnitude higher than that of p-type! www.longigroup.com Page 12 Cs Reduction Thermal Donor Control Defect Engineering Low Metal Contamination Oi Reduction HQ Wafer Key Improvement Factors 3. Challenge and Solution for HQ Wafers www.longigroup.com Page 13 Low Metal Contamination CZ Pulling Process • Improve environment cleanliness • Optimize crystal pulling process • Upgrade automation level • R&D of handling tools (poly and hot zone parts) Cleaning and Crushing of Recycled Poly • Improve classification and cleaning process • R&D of new crusher and process. Poly Silicon • Improve poly purity standard • Improve classification standard of recycled poly Hot Zone • Large scale application of high purity materials • Improve use and management of hot zone materials • R&D of high purity new materials (including crucible) Purity Improvement www.longigroup.com Page 14 Poly Silicon Purity Control 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0% 6% 11% 16% 22% 27% 32% 38% 43% 48% 54% 59% 65% 70% 75% 81% 86% 91% 97% Ingot length(mm) Res.: 0.8~1.8Ω.cm Lifetime(μs) Ingot MCL rely on poly silicon quality 8648 7386 6792 7685 4965 6300 A B C D E F Ingot MCL rely on poly silicon quality Ave. Lifetime （μs ）  Ingot MCL is sensitive to poly silicon purity.  Chinese domestic poly silicon quality needs to be improved further for higher MCL magnitude. www.longigroup.com Page 15 Poly Silicon Crushing and Cleaning Management 7973 7397 7000 7200 7400 7600 7800 8000 8200 X-1 X-2 LIFETIME/US Different crushing methods 7.8% Old process New Process Lifetime/us +10% Different cleaning methods  Recycled poly silicon crushing is an key process for metal impurities introducing.  Poly silicon cleaning is another process to introduce metal impurities, which results in low minority lifetime. www.longigroup.com Page 16 不同厂家热屏金 属含 量对 比 ( 单 位ppm) Hot Zone Purity Improvement 不同纯度热屏对 单晶 品质 影 响  Reflector purity contributes a lot to MCL performance  Although not shown here, crucible purity must be controlled to reduce metal impurity. Metal impurity comparison of different reflector suppliers (Unit: ppm) Ingot MCL performance of using different reflectors Metal A Supplier B Supplier C Supplier 铁（Fe ） 0.01 0.07 0.01 钛（Ti ） 0.01 0.05 0.02 钒（V ） 0.01 0.01 0.62 镍（Ni ） 0.01 0.05 0.58 钼（Mo ） 0.05 0.05 0.41 钨（W ） 0.05 0.05 0.31 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Lifetime (μs) A Supplier B Supplier C Supplier www.longigroup.com Page 17 Old-Design New-Design 坩埚溶解 SiO 2(s) ↔ 2O (l) +Si (l) Oxygen Concentration Reduction Optimization of crystal pulling process: Smooth air passage can increase the volatilization of oxygen Optimization of hot zone design: Adjusting melt convection mode Reduce oxygen generation: Improving the quality of crucibles Ref: A.N. Vorob’ev, A.P. Sid’ko, V.V. Kalaev, J. Crystal Growth 386 (2014) 226–234 www.longigroup.com Page 18 0.0 0.5 1.0 1.5 2.0 2.5 0 2000 4000 6000 8000 10000 0% 50% 100% N-Type Lifetime/μs Res./Ω.cm Thermal Doner (TD) Reduction  TD relies on oxygen concentration and thermal history of ingot (wafer).  High TD density results in a clear MCL dropping at N-type ingot seed end.  TD density impacts HJT cell efficiency a lot~there is 1% CE drop when TD density close to 1*10 15 cm -3 . Lifetime Res. www.longigroup.com Page 19 0 2 4 6 8 10 12 14 16 18 20 Seed end brick2 brick3 brick4 brick5 brick6 brick7 Tail end Normal Technology Improved Technology Ultra low oxygen Ultra Low Oxygen TD BMDs OISF … Normal Production Improved Technology Oi(ppma) LONGi Oxygen Capability www.longigroup.com Page 20 N-type 0 2000 4000 6000 8000 10000 12000 Seed End Brick 2 Brick 3 Brick 4 Brick 5 Brick 6 Brick 7 Tail End MCL O(us) MCL N(us) Traditional Pulling technology Note: N-type ，BCT400 test ； Res. 1-7 ohm.cm Updated pulling technology LONGi MCL Capability www.longigroup.com Page 21 4. Future Trend for N-type Wafer: Resistivity Thickness Dimension (Size) www.longigroup.com Page 22 Resistivity Shipment Information 4% 46% 26% 13% 30% 27% 15% 12% 9% 15% 13% 7% 3% 12% 21% 18% 25% 8% 2% 1% 8% 5% 6% 11% 6% 25% 15% 37% 32% 38% 49% 38% 36% 33% 53% 28% 14% 13% 26% 35% 28% 39% 59% 44% 2018-01 2018-02 2018-03 2018-04 2018-05 2018-06 2018-07 2018-08 2018-09 2018-10 0.3-2.1 1-7 1-8 1.5-7 0.5-3.5 1.5-12 0.2-2 0.15-2 1.7-13  Resistivity relies on cell structure/technology: IBC, N-PERT, HJT…  High efficiency cell prefers to use lower resistivity substrate. www.longigroup.com Page 23 Resistivity  HJT cell simulation results show resistivity and MCL impact on HJT efficiency (lower Res and higher MCL result in higher efficiency, Ref: MEMC workshop, 2012).  Lower wafer resistivity (0.2~2 ohm.com, compared with 0.5~4 ohm.cm) results in a higher FF and higher cell efficiency. www.longigroup.com Page 24 Resistivity  Lower wafer resistivity (0.2~2 ohm.com, compared with 1~7 ohm.cm) results in higher cell efficiency (~0.4%). 0 0.1 0.2 0.3 0.4 0.5 0.6 Frequency Ingot #1 0.2 - 2 Ohm.cm Ingot #2 0.2 - 2 Ohm.cm Ingot 1 - 7 Ohm.cm 22.5 % 22.1 % www.longigroup.com Page 25 Resistivity  At certain doping level, the dopant concentration (resistivity2000 is qualified for mass production, almost no cell efficiency and FF difference when LT/Res4000.  Ref: Jun Zhao, LONGi Silicon-MB R&D collaboration result. www.longigroup.com Page 26 THICKNESS MATTERS… www.longigroup.com Page 27 150μm 10μm 10μm 10μm poly$ returns poly$ returns poly$ returns Thinner Wafer 110μm Wafer / Cell cost ~61% （2011.1 ~73% ） Wafer / Module cost ：~32% (2011.1： ~55% ） Poly / Wafer cost ：~56% （2011.1： ~47% ） www.longigroup.com Page 28 Smaller Core Wire Diameter  Low cost DW supply.  DW core wire diameter down to 50 um is on-going for less poly usage. www.longigroup.com Page 29 P-Type Thinner Wafer: Shipment Information  180μm dominates the market, but the proportion for 160um increases rapidly from Q4’2018. www.longigroup.com Page 30  N-type substrate: the use of a boron-doped front emitter with rear side phosphorus- doped BSF offers a bifacial type cell structure which can be fabricated on thinner wafers.  Wafer thickness down to 130 um for 6 inch mass production, and 150 um for 8 inch mass production. N-Type Thinner Wafer: Shipment Information www.longigroup.com Page 31 Ref: J.Zhao. Et al. 24% silicon heterojunction solar cells on Meyer Burger’s mass production tools and how wafer material impacts cell parameters Thinner Wafer: N-Type Advantage  Wafer thickness down to 120 um shows no cell efficiency degradation. www.longigroup.com Page 32 SIZE MATTERS… www.longigroup.com Page 33  Wafer area (power output): Side length (L) matters  Wafer cost: Diameter (D and d) matters Larger Size Wafer d D L Full Square (FSQ) Quasi-Square (QS) www.longigroup.com Page 34 Wafer Size www.longigroup.com Page 35 Wafer Size: Standardization M2 M4 166 +5mm +5mm WHY NOT define standard module sizes? What is the next? 158.75 FSQ, M4, or M6 (166)? MARKET www.longigroup.com Page 36 P-type Wafer Size: Shipment Information  M2 still dominates the market, the market share of FSQ is increasing dramatically from Q4’2018. www.longigroup.com Page 37  M4 fluctuation is caused by order/commercial issue instead of production problem  M2 and M2+(157.35X211) are the main sizes with ~90% shipment. N-type Wafer Size: Shipment Information www.longigroup.com Page 38 LONGi Silicon Capacity Expansion Plan  Continue to expand capacity up to 45 GW by 2020E.  All pullers can be easily converted to N-type without additional investment.  All equipments (include puller and DW machine) can be used for big size wafer manufacturing (up to 166 mm side length). www.longigroup.com Page 39 High Eff Customization Low Cost To improve the material quality (MCL, etc.)… Thin wafer is the solution to scaling down the cost, ecnomic of scale… Resistivity, dimension, other parameters… Summary 隆基与您同行！ Thanks for your attention! 善用太阳光芒 创造绿能世界 Utilizing solar energy, Building a green world 我们致力：成为单晶硅产品的领航者，为全球光伏电站贡献更高效率。 我们致力：成为光伏产业忠实的伙伴，为客户投资创造更大价值。 我们致力：推动光伏产业发展，为子孙后代创建绿色地球。