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Authors Shravan K. Chunduri, Michael Schmela 2018 Edition PERC How To Improve High Efficiency Crystalline Solar Cells PERC Solar Cell Technology2 TaiyangNews | PERC Solar Cell Technology 2018 PERC Solar Cell Technology 2018 | TaiyangNews 3 04 PERC Performance 24 06 PERC Improvements 33 © TaiyangNews 2018 All rights reserved. The text, photos and graphs in this report are copyrighted cover photo credit Jinergy. TaiyangNews does not guarantee reliability, accuracy or completeness of this report s content. TaiyangNews does not accept responsibility or liability for any errors in this work. Publisher TaiyangNews UG haftungsbeschraenkt Montsalvatstr. 15 80804 Munich, Germany www.taiyangnews.info TAIYANGNEWS ALL ABOUT SOLAR POWER 02 About PERC 8 2.1 What is PERC 2.2 Processing PERC 07 PERC 35 05 PERC in Production 26 60-cell solar modules 72-cell solar modules PERC Capacities Production 01 Introduction 6 Leadmicro p. 2 RCT p. 5 LONGi p. 7 Micromac p. 9 Astronergy p. 11 DKEM p. 21 Innolas P. 23 Heraeus p. 25 DuPont p. 27 CSPV p. 32 Von Ardenne p. 38 Jinergy p. 44 SNEC p. 47 APVIA p. 56 Advertisers Contents 08 Beyond PERC 39 03 Manufacturing PERC 10 3.1 Passivation Materials 3.2 Deposition Technologies 3.3 Aluminum Paste Approach 3.4 Laser Contact Opening 3.5 Rear polishing 3.6 Metallization 09 Conclusion 46 10 10.1 Interview - Dupont 10.2 Interview - DKEM 48 8.1 n-PERT 8.2 n-PERL 8.3 Passivated Contacts 8.4 Heterojunction TechnologyHJT 7.1 Bifacial PERC 7.2 Multi PERC 7.3 Selective Emitters4 TaiyangNews | PERC Solar Cell Technology 2018 Executive Summary It didn’t take long after commercialization of PERC solar technology really started Last year, we entered the PERC era in the solar cell technologies segment. And today, PERC is the new standard – at least for monocrystalline cells, which is on its way to becoming the leading crystalline cell species. While cell manufacturers continue to expand into standard PERC, several stakeholders involved in solar cell production are offering and working on processes and materials to bring PERC to the next level. That’s why our PERC 2018 report is looking at PERC, that’s for us everything supporting basic PERC to improve efficiency and yield – from selective emitters to bifacial technology. As many researchers and companies are also looking into cell technologies that could compete with PERC today or succeed it tomorrow, we are briefly analyzing these candidates as well. Chapter 1 – Introduction to PERC Several attempts to introduce new cell structures to the PV industry were not very fruitful, but for PERC it simply worked. It is primarily because the technology requires adding only 2 pieces of equipment to the standard aluminum-BSF and the efficiency gain is up to 1 absolute. This made it simply irresistible for cell makers, especially those that were looking for higher efficiency products. PERC is all about adding rear passivation to the rear side of the cell replacing the aluminum BSF. While that’s all in theory, for practical purposes, the rear passivation film is opened with lasers to give a way to the rear metal to contact silicon. The chemical wet-bench based edge-isolation step is tweaked for rear polishing. Chapter 2 – About PERC The key to PERC manufacturing is rear passivation, whereas the unanimous material of choice for this purpose is aluminum oxide, which can be deposited using PECVD machines, well-known from applying silicon nitride, or Atomic Layer Deposition ALD tools. The aluminum is typically capped with silicon nitride for all practical purposes. PECVD is still having the largest market share, but ALD suppliers have found an entry into the market as well. Batch type time based ALD systems are evolving very strong with a high throughput advantage. Leadmicro, which has provided data for our report for the first time, is one of the companies offering tools based on batch configuration. Batch tools have an inherent limitation of undesired deposition of aluminum oxide on the front side called “wrap around.” There are cell producers who ignore this limitation and put aluminum oxide on both sides. But there are also equipment makers who address this issue, like SoLayTec and Levitech, which have developed spatial ALD systems that execute single side deposition. Ideal Energy from China developed a hybrid system that combines an inline PECVD transport principle with spatial ALD. Leadmico is offering a similar system. However, aluminum oxide layers deposited with ALD tools require capping silicon nitride for which again PECVD systems are needed. One undeniable advantage with PECVD is it allows the deposition of aluminum oxide and capping layer in one go. The choice here is direct plasma, offered by Centrotherm and newcomer Fullshare, which is in the process of commercializing its production tool. Meyer Burger is the only player in the remote plasma area. Both Meyer Burger and Centrotherm have improved their tools to support higher throughput. Apart from productivity reducing, aluminum oxide film thickness, lowering the precursor TMA consumption and improving the uptime are the most common subjects every tool suppliers are working on. Laser contact opening and rear polishing are two steps in the manufacturing of PERC that have evolved to be very robust. Metallization is another crucial step in PERC processing. Chapter 3 – Manufacturing PERC PERC is high on the hit list of record efficiencies. In the last 12 months, the world record was broken 6 times. Today’s highest efficiency PERC cell of 23.95 was made by JinkoSolar, followed by a 23.6 cell from LONGi. Chapter 4 – PERC Performance When it comes to production of PERC panels, the general metric is rather module power than cell efficiency. And several advancements in module design are pushing the module power rating upwards. More busbars, multi busbars and half cut cells are increasingly adapted for PERC modules. We have summarized t Enjoy reading our PERC Solar Cell Technology 2018 Report Shravan K. Chunduri Head of Technology, TaiyangNews shravan.chunduritaiyangnews.info 91 996 327 0005 Hyderabad, India Michael Schmela Managing Director, TaiyangNews michael.schmelataiyangnews.info 49 173 15 70 999 Munich, GermanyPERC Solar Cell Technology 2018 | TaiyangNews 5 the top PERC module efficiencies from leading module manufacturers. The most powerful 60-cell module in our list has 340 W, the highest power rating for a 72-cell equivalent of 144 half cells reaches 400 W Chapter 5 – PERC in Production. PERC has improved significantly since it entered mass production 6 years ago. We have summarized the PERC developments and incremental changes to improve the technology Chapter 6 – PERC Improvements. PERC has many opportunities to be tweaked to the PERC level. Examples for PERC are bifacial PERC, black silicon texturing and a PERCT structure. But no technology will last forever. Thus we have briefly looked at possible candidates to replace PERC. This includes n-PERT, n-PERL, passivated contacts and heterojunction technology Chapter 8 - Beyond PERC. With metallization pastes playing a key role for solar cells in general and PERC in particular, we have interviewed executives from a global market leader and pioneer in this field DuPont and a rising star from China DKEM. RCT i-BlackTex Inline Wet Chemical Process · 1-1.5min black silicon texturing time · Excellent Cleaning Inline tool length 13m 3600 w/h Low running cost · No expensive, unstable H ² O ² · No organic additives · No changes to facilities required Silver recovery unit available RCT Solutions GmbH Line-Eid-Straße 1 D-78467 Konstanz, Germany inforct-solutions.com www.rct-solutions.com The Technology Company Black Silicon for DWS multi wafers Unique inline process and equipment for texturing of diamond wire sawn wafers is finally available. Picture DWS wafer textured by RCT „Black Silicon“ Process Download your free copy of the TaiyangNews Reports and Market Surveys on our website www.taiyangnews.info www.taiyangnews.com.cn and wechat Channel 微信公众号 WeChat6 TaiyangNews | PERC Solar Cell Technology 2018 1. Introduction Who would have thought this only 5 years ago Last year, we entered the PERC era in the solar cell technologies segment. And today, PERC is the new standard – at least for monocrystalline cells. While in 2017, less than 20 of total crystalline silicon cell production was PERC, this year global cell factories’ output is expected to reach close to 50. And the high-speed trip of PERC seems to be far from ending. While cell manufacturers continue to expand into standard PERC, several stakeholders involved in solar cell production are offering and working on processes and materials to bring PERC to the next level. That’s why our PERC 2018 report is looking at PERC, that’s for us everything supporting basic PERC to improve efficiency and yield – from selective emitters to bifacial technology. As many researchers and companies are also looking at cell technologies that could compete with PERC today or succeed it tomorrow, we are briefly analyzing these candidates as well. While everyone involved in wafer, cell and module production is not only talking about PERC, but about PERC or even on how to go beyond PERC today, the concept is everything but new – in fact, it is an over 3 decades old concept. Leading PV scientist Martin Green and his associates from the University of New South Wales in Sydney have first proposed this concept in 1983 and published a technical paper in 1989, when they announced a then world record efficiency of 22.8. While modules made with these record cells served some niche applications, such as solar racing cars, this technology was not able to enter the mainstream. After the big crisis from 2011-2013, the first cell manufacturers started to upgrade their lines with PERC. A big chunk of new cell production capacity announced in 2015 – and implemented in 2016 – was based on PERC architecture. This trend towards PERC has continued for both upgrades of old lines as well as cell expansions to satisfy demand for solar, which has been growing much faster than everyone anticipated in the last few years. That’s why our original 2017 estimates for PERC cell production output and capacities had to be revised upwards – and why we are even more upbeat for 2018 and beyond. While we have been seeing continuous new announcements of PERC cell efficiency improvements over the last few years, recent months have been especially exciting in this regard, with LONGi and JinkoSolar pushing the record efficiencies to completely new heights. Using several PERC methods, as of May 2018 the world record for a commercial-size PERC cell is now close to 24. After the huge potential of PERC technology motivated us to prepare a first in-depth report in early 2016, we looked in our second report in 2017 at a quickly maturing segment with continuous improvements on all fronts. Now, in our 2018 report, we see interesting new players pushing into the PERC segment, while ‘incumbents’ are trying to defend their market shares. At the same time, dynamics in PERC processing equipment are somewhat changing to different technologies. There are many new and upgraded production machines being introduced this year. Looks like there’s still a lot to explore about PERC – the new standard in crystalline silicon cell technology. PERC push LONGi, the world’s leading mono wafer manufacturer, has been one of the main driving forces towards PERC technology. Source © TaiyangNews 2018PERC Solar Cell Technology 2018 | TaiyangNews 7 8 TaiyangNews | PERC Solar Cell Technology 2018 2. About PERC When TaiyangNews published its first report on PERC in early 2016, the technology was in the early stages of commercialization and many process related details were not known. Today, PERC is the new standard for monocrystalline solar cells. Still, as the global solar market grew again around 30 last year to over 98 GW in 2017 and many new participants have and are joining the continuously growing solar field, we also include in our third PERC report a brief introduction to PERC technology while more detailed basics can be found in our previous two PERC reports, which are still available for download online. 2.1 What is PERC In brief, PERC is a cell concept that increases efficiencies up to 1 percentage point by adding only 2 different equipment parts and can be produced at competitive cost compared to standard cells. That explains the successes of the technology and why so many cell manufacturers jumped on the PERC train when the last investment cycle for capacity expansions had started a few years ago. Turning to the Dark Side While in the past the bulk of improvements that led to continuous performance gains of solar cells were on their sunny side, a few years ago, the PV industry shifted its focus to the rear side. As of that point, it was primarily about passivating the rear surface of a solar cell and accordingly modifying the metallization scheme. These rather simple changes adapted to standard solar cell processing entitle the produced silicon slices for a new name – PERC, which stands for Passivated Emitter and Rear Cell. Process Sequences for Production of PERC Cells Texturing on both sides Phosphorus diusion tube furnace Process required to be optimized for PERC Single-side etching and edge isolation Front side silicon nitride ARC and passivation layer deposition Deposition rear surface passivation stack - aluminum oxide capped with silicon nitride Opening rear passivation stack with lasers Two additional process stapes required for PERC Front metallic contact ARC passivation lm nphosphorus diused emitter Local AI BSF formed through laser opening of near passivation stack Rear passivation stack Rear contact Fully processed PERC cell after metallization Not much different A cell line for PERC technology requires only two pieces of additional equipment compared to a standard line - devices for rear passivation and laser structuring, as shown in this process flowchart. This means upgrades to PERC are simple, and even a complete PERC line doesn’t cost much more. Process Sequences for Production of PERC Cells microCELL TM Highly Productive Laser Systems for Cell Processing Versatile laser processing platforms » Laser contact opening LCO » Half cell cutting by TLS » Patterning, doping, and annealing » Upmost throughput in the market » Unbeatable cost-benefit ratio www.3d-micromac.com Source © TaiyangNews 2018PERC Solar Cell Technology 2018 | TaiyangNews 9 The PERC structure is a natural progression from the standard Back Surface Field BSF cell architecture. This BSF-based cell type suffers from some inherent limitations, which are becoming more apparent with the industry’s focus to increase cell efficiencies. The metallic alumin