Efficiency roadmap of PERC learned from free energy loss analysis-孟夏杰-隆基.pdf
en.lerri.com Efficiency roadmap of PERC learned from free energy loss analysis Meng Xiajie 14th CSPV en.longi-solar.com en.longi-solar.comPage 2 ONTENTS 目录C I. Industrial Technology of High Efficiency PERC Cells II. Realizing 23.6% Efficient Industrial PERC Cells III. Efficiency Limit of Industrial PERC Cells IV. Industrial Technology of Post-PERC Cells en.longigroup.comPage 3 en.l ngi-solar.com Texturing Low pressure diffusion SE Laser doping Etching & polishing Rear Side passivation Antireflection coating Laser ablationPrinting & firingHydrogenation BSF process High EFF PERC process Industrial Technology of High Efficiency PERC Cells Selective emitter： 100-150Ω /□ for non-contact area, 50-80 Ω /□ for contact area Lower emitter recombination J0 Rear local contact: Reduced hole transportation Resistance Improved rear contact recombination and non- contact area passivation en.longigroup.comPage 4 en.l ngi-solar.com Industrial Technology of High Efficiency PERC Cells LONGi’s high efficiency PERC cells—— mono and bifacial Bifacial PERC 22.0%(Front), 75% BiFiMono Facial PERC 22.4% Key issues from PERC to BiPERC Optimized rear etching process for reduced front optical transmission and re BiFi Optimized wafer parameter, Al grid and laser process for high BiFi performance Optimized dielectric stacks for better passivation, Si- Al2O3 interface protection and uniform rear appearance en.longigroup.comPage 5 en.l ngi-solar.com Industrial Technology of High Efficiency PERC Cells LONGi’s high efficiency PERC products High efficiency and low LID： • 22.4% mass production efficiency • Average cell LID 0.6-1.2% after hydrogenation LID Performance Tracking LID testing condition: 5kW/h, 75℃Module power generation guarantee： • Average power up to 315W for 60 cells module • 30 years power guarantee 84.95% en.longigroup.comPage 6 en.l ngi-solar.com Industrial Technology of High Efficiency PERC Cells Mass production efficiency of PERC cell in LONGi 20.80% 21.20% 21.60% 22.00% 22.40% 22.80% 23.20% E F F （ % ） PERC Cell production line efficiency tracking 2stGen PERC PERC upgrade 1 st Gen PERC 3stGen PERC 研发中 Developing 16.09 17.01 17.04 17.08 17.12 18.06 en.longigroup.comPage 7 en.l ngi-solar.com Industrial Technology of High Efficiency PERC Cells PERC record efficiency in LONGi 22.17% 22.43% 22.61% 22.71% 23.02% 23.26% 23.60% 23.75% 23.83% 22.18% 22.41% 23.68% 22.00% 22.20% 22.40% 22.60% 22.80% 23.00% 23.20% 23.40% 23.60% 23.80% 24.00% Jan-17 Mar-17 Apr-17 Jun-17 Aug-17 Sep-17 Nov-17 Dec-17 Feb-18 Apr-18 May-18 PERC效率 BiPERC正面效率 The world record of large area PERC cell efficiency has been renewed by LONGi for several times. Since our newest announcement 23.6%, the top efficiency climb toughly towarding 24%. 效率 正面效率 Data source: CPVT, Fraunhofer ISE en.longigroup.comPage 8 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Loss analysis of PERC cells Optical, electrical parameters are measured on special samples by QSSPC, PL, QE, SunVoc, TLM etc. Loss analysis simulated by Quokka3 varies input. New process and technology are developing to enhance the efficiency of mass production continually. P Saint‐Cast et al, physica status solidi (a), 2017, 214(3): 1600708 R. Brendel et al. Theory of analyzing free energy losses in solar cells. APL 2008 97(173503) FELA: Free energy loss analysis CLA： Current loss analysis en.longigroup.comPage 9 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Loss analysis of production and champion cells 40.6 41.6 1.6 1.7 1.3 1.3 0.9 0.7 2.3 1.4 36.0 38.0 40.0 42.0 44.0 46.0 48.0 Production Champion Current Loss(mA/cm2) Cell Current NIR parasitic absorb Front surface escape ARC reflectance Metal shading 0.64 0.54 0.37 0.31 0.18 0.13 0.17 0.16 0.05 0.04 0.28 0.29 0.25 0.05 0.24 0.23 0.19 0.19 0.05 0.05 - 1.00 2.00 3.00 Production Champion Power Loss(mW/cm2) front trasport recombination bulk recombination rear dielectric recombination front contact recombination rear contact recombination front transport resistance Grid resistance rear contact resistance bulk resistance front contact resistance Resistance Loss Recombin ation Loss Voc（ V） Isc（ A） FF（ %） Eta（ %） Mass Production 0.6826 9.85 81.42 22.43 Champion Cell 0.687 10.1 83.02 23.60 en.longigroup.comPage 10 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Approach to reach 23.6% • From 22.4%, cell efficiency can be improved to 23.6% by extra technical approach such as multi busbars， advanced front anti-reflection coating, improved rear contact geometry, improved from emitter/grid, advanced hydrogenation and Si material. 23.6 Multi Busbar AR coating Rear contact and passivation Wafer & hydrogenation &improved emitter en.longigroup.comPage 11 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Big Steps of the process optimization Selective Emitter Jsc Voc FF eta mA/cm2 V % % 40.38 0.6721 81.16 22.02 40.65 0.6803 81.01 22.40 Selective emitter is not only creating a high-low diffusion structure, but also gives the room for better application of narrow fingers grid. Since the doping is high enough for ohmic contact, better paste conductivity with good aspect ratio is possible for this application. - 0.50 1.00 1.50 Non-SE SE 1.17 0.85 Front illumination: Fingershading CLA(mA/cm2) - 0.20 0.40 0.60 Non-SE SE 0.59 0.35 full area front skin (NonContacted): TotalRecombination FELA(mW/cm2) en.longigroup.comPage 12 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Big Steps of the process optimization MBB Grid resistivity simulation in unit of ohm.cm2 Total grid resistivity decline from 0.238 to 0.066 ohm.cm2 Less busbar shading Jsc Voc FF eta mA/cm2 V % % 40.65 0.6803 81.01 22.40 41.14 0.6806 81.93 22.94 - 0.50 1.00 1.50 2.00 2.50 5BB MBB 2.02 1.50 Front illumination: front surface transmission CLA(mA/cm2) - 0.10 0.20 0.30 0.40 5BB MBB 0.36 0.10 ExternalCircuit: Rseries FELA(mW/cm2) en.longigroup.comPage 13 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Big Steps of the process optimization ARC Some ideal ARC can be used instead of SiNx. If one looks back to the days of SiNx is developed for crystalline silicon, 30 nm thick SiNx is enough for field/hydrogen passivation of n-diffusion. SiNx n-Si ARCJsc Voc FF etamA/cm2 V % % 41.14 0.6806 81.93 22.94 41.45 0.6807 81.92 23.11 - 0.50 1.00 1.50 2.00 2.50 5BB MBB ImprovedARC 2.02 1.50 1.18 Front illumination: front surface transmission CLA(mA/cm2) p-Si en.longigroup.comPage 14 en.l ngi-solar.com Realizing 23.6% Efficient Industrial PERC Cells Big Step of the process optimization Rear Dots/Paste Jsc Voc FF eta mA/cm2 V % % 41.45 0.6807 81.92 23.11 41.48 0.6828 82.58 23.39 Dot like contact is often claimed for PERC rear application. The problem is that how far the laser process and paste co-firing can go to make it “pinhole” conducting like. - 0.10 0.20 0.30 0.40 0.50 0.60 0.70 Line Dot 0.70 0.48 Domain: CurrentTransport (Resistive) FELA(mW/cm2) en.longigroup.comPage 15 en.l ngi-solar.com Efficiency Limit of PERC Cells Loss Analysis of 23.6% Champion Cell There’s still room to improve from 23.6% Current loss: metal shading, front reflection, and parasitic absorb. Recombination loss: front emitter transport and bulk material Resistance loss: lateral transportation， bulk resistivity and rear contact 0.54 0.31 0.13 0.16 0.04 Recombination Loss(mW/cm2) front trasport bulk rear dielectric front contact rear contact 0.29 0.05 0.23 0.23 0.05 Resistance Loss(mW/cm2) front transport Grid rear contact bulk front contact 1.72 1.32 0.67 1.41 Current Loss(mA/cm2) NIR parasitic absorb Front surface escape ARC reflectance Metal shading en.longigroup.comPage 16 en.l ngi-solar.com Efficiency Limit of PERC Cells Achieve the efficiency limit of industrial PERC cells 24.0 Fine line metallization Real local contact passivation Eff ici en cy % Approach to make PERC EFF up to 24% Fine line metallization， less shading and contact recombination loss Passivation emitter real local（ PERL） Front passivation contact Front Passivation contact en.longigroup.comPage 17 en.l ngi-solar.com p-TOPCon n-TOPCon p-POLO IBC Tandem 32.8% 2J 35.9% 3J η=26.1% η=24.3% η=25.7% Poly Si Passivated contact technology have the largest potential to be applied in the nearest future. High efficiency technology with industrial potential Industrial Technology of Post-PERC Cells ~23% monoPolyTM Shubham， SERIS Armin Rithter, ISE Armin Rithter, ISE Felix, Robby, ISFT en.longigroup.comPage 18 en.l ngi-solar.com Topic on LID of LeTID standard LeTID has dragged attraction in IEC standards on cell and module level. Some preliminary standards claim that 75℃ seems an appropriate temperature to propagate LeTID effects.t. How often do 75℃ actually occur in the field? Ask PV system guys, and check your data! If 75℃ do not/rarely occur in the field, why we use it in a standard? Can the scientific community explain in solid engineering what is the driving force of LeTID? BO-LID is affected by oxygen and boron concentration. The BO-LID generation is speed up by carrier injection level. However, it is also affected by doping level and temperature. That’s why we are lucky today, most of us is doing carrier induced regeneration during PERC process in our products. Is it the same scenario on LeTID? Is it affected by carrier injection density, dopant concentration and temperature. If yes, we can only choose a reasonable injection level seen in the field. Can we clearly distinguish LID (BO-LID) and LeTID by measurement method？ I suppose not. Is 1A or 0.1sun appropriate for LeTID testing distinguish? When the module is illuminated by 0.1 sun, what about the temperature? Is it around 50℃ ？ Does LeTID actually occur below 50℃ ？ If we are using 10A or 1sun for LeTID testing, the temperature will be/maybe 75? The BO will be regenerated, that’s actually the carrier induced regeneration we are doing in industry. The process is also helpful for anti-LeTID. So again can we distinguish BO-LID and LeTID? Do we really need a standard for module or cells? It takes extra 1000hours to finish a testing. The cost is high. Does LeTID shoes the real scenario for long term LID stability? en.longigroup.comPage 19 en.l ngi-solar.com 33 38 43 48 53 58 63 68 6/5 6/12 6/19 6/26 7/3 7/10 7/17 7/24 7/31 8/7 8/14 8/21 8/28 日最高温度曲线 LR295 LR290 JK270 TR260 环境温度 温度 ℃ 吐鲁番组件背板温度测试结果 26.0 31.0 36.0 41.0 46.0 51.0 6/5 6/12 6/19 6/26 7/3 7/10 7/17 7/24 7/31 8/7 8/14 8/21 8/28 日平均温度曲线 LR295 LR290 JK270 TR260 环境温度 组件类型 环境温度 双面 LR295 PERC单面LR290 多晶 JK270 多晶 TR260 最高温度 42.3 63.3 61.6 62.1 62.1 平均温度 36.7 43.6 42.7 42.9 43.1 • Do we need a passing criteria or standard on light induced degrade on elevated temperature? 谢谢观看 !THANKS! 地址：陕西省西安市经济开发区尚稷路 8989号 电话： 4009696199 传真： 029-86686228 ADD:Block B, No.8989 Shangji Road, Xi an Economic And Technological Development Zone, Xi an, Shaanxi, China. TEL: +86-400969619 FAX: +86-29-86686228 en.longi-solar.com
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