A Review of Laser Processes Used in Solar Cell Fabrication

A Review of Laser Processes Used in Solar Cell Fabrication Abstract There are many different laser techniques that can be used in the production of solar cells. By examining the research which the various solar cells were fabricated with laser technique, it is possible to understand the pros and cons of using laser for produce the cells. The following paragraphs will list which process the laser technique have been used in this review. Introduction

The buried contact solar cell was invented at University of New South Wales by Green et al. in 1983. These solar cells have a relatively high efficiency approximately 25% and present a possibility of cost-reduction with applying this technology to the manufacturers’ production lines. The following are the general main steps of forming the buried contact solar cell: 1. Texturing of surfaces 2. Top surface diffusion 3. Oxide growth 4. Groove cutting and diffusion 5. Aluminum deposition and sinter 6. Metal plating 7. Edge isolation

The key parts of this process, which result in the cells become more efficiency than the standard screen printing solar cells are the laser grooving and groove diffusion to reduce the cell shading and contact resistance and the texturing which reduce the surface reflection. A schematic of a buried contact solar cell is shown in the figure below (Green 1995). [pic]Figure 1: Cross-section of buried contact solar cell Research continues working on the ways which could further improve the efficiency of the buried contact solar cell.

With the statistics obtained from the experiment, they can try to figure out the effects which using different methods and materials in solar cells would cause. These parts include different diffusion profiles to form the p-n junction, surface passivation using different materials, and the different methods of grooving of the silicon, rear surface treatment, metallization and so on. Laser texturing In order to reduce the reflection effect of the solar cells, front surface texturing is one solution. There have many methods to increase the light trapping, such as mechanical scribing and reactive ion etching.

However, laser texturing could effectively texture the multicrystalline surface, providing isotropic etching that other techniques cannot do. Abbott and Cotter (2006) revealed that with deeper laser texturing, the less the front surface reflection is. More detailed results are shown in figure 2 (adapted from Abbott and Cotter 2006). Note that with very shallow texturing (10mm), they cannot trapping very well, as a result behaving like the planar one. Figure 2: Front surface reflection of laser textured samples with different ablation pit depths (0) 10mm, (? 20mm, (? ) 30 mm, (*) 40 mm, (x) 50mm with residual slag, (+) planar silicon and (line) random pyramid textured silicon. It is straightforward that we should texturing deeper pit, however, this will increase the surface recombination rate, which is detrimental to solar cells. Even though the pit depths 50mm have the lowest reflection, it will leave some slag in the pits that acting like defects. These residual slags will enhance the surface recombination rate, reducing the open-circuit voltage as well as the efficiency of the solar cells.

Finding better parameters of operation to texture the wafer properly without the appearance of slag is therefore becomes the main issue for the manufacturers. Top Surface diffusion The conventional method for doping materials is the thermal diffusion which performed at high temperature (over 800? ). The process is so-called solid state diffusion and has various methods, for instance physical vapour deposition, to control the doping profiles. Also there is a considerable alternative method of forming doping areas in silicon solar cells by using laser-doping.

With the Nd:YAG pulsed laser, the doping profiles can be controlled with the desirable doping area. Ogane et al. (2009) asserted that by using the laser doping technique with 0. 5W output, it can fabricate the solar cells with comparable efficiency to those fabricated by thermal diffusion methods. Some statistics of the result from their research are shown in figure 3 (adapted from Ogane et al. 2009). Note that a large number of the oxygen atoms are induced to the solar cells owing to the operation is in air. This increase the sheet resistance and as a result, reducing the efficiency of the solar cells.

The advantages of the laser doping process are that it can be operated at room temperature, in the atmosphere, as well as the easier process forming a selective doping area without any lithography pre-set processes. With these advantages, even though the properties of these solar cells are slightly worse than the cells handled by thermal diffusion, it is acceptable to some manufacturers and worthy to work on it. [pic] Figure 3: The average of six solar cells properties of cells with emitters fabricated by laser doping as a function of laser output power, compared with the case of thermal diffusion (TD).

Laser groove The most common device which is used to form the laser grooved front surface contacts is the Nd:YAG pulsed laser, operating at a high frequency. The depth of the laser groove after lasing is typically 30 microns deep and approximately 20 microns wide. During the process, laser will vaporises silicon through the oxidation layer, and this will induced the thermally damaged to silicon. Such this damage will acts as recombination sites of carriers when operating the solar cells, minimised this defect is therefore necessary in order to improve the efficiency of the solar cells.

Studies on this part (Schoonderbeek et al. 2007) have revealed that using the shorter wavelength of the laser, i. e. the higher power output can reduce the thermal damage induce by the laser. [pic] Figure 4: Increased lifetime ratios (decreased laser damage) are obtained when scribing lines using short-wavelength lasers. Figure 4 (adapted from Schoonderbeek et al. 2007) above shows that by using lasers with short-wavelength at either 532nm (green) or 355nm (UV) will have better properties in comparison to 1064nm (IR) laser. Nevertheless, the lower cost of the IR laser is more favourable to the manufacturer.

Thus the solar cell research of this part is undertaken at institutions and companies in order to find out the better trade-off point. Back surface field and laser-fired contacts The technology which usually used for rear contact passivation in solar cells is that highly doped region near the back contact. This is called back surface field. Normally aluminium is applied to it by evaporation, following by sintering to make aluminium atoms diffuse into the silicon. For reducing the cost per watts generated by solar cell, some different methods were tested for the feasibility analysis.

One of the ways for reducing the cost is doping aluminium locally (Meemongkolkiat et al. 2006). It is obviously that doping less metal could reduce the cost, however the efficiency should not be diminish too much. In this process the oxide on the back surface is partially etched prior to aluminium were screen-printed on it. In their research, with choosing the aluminium screen-printing pastes properly (the composition is not provided in their paper), the efficiency of the solar cells are adequately (16%) compared to the normally full back surface field (16. %). Alternatively, aluminium deposition can be applied to the solar cell with the passivated emitter and rear contact, followed by fast scanning laser firing to reduce the rear surface recombination rate as well as improve light trapping. With this so-called laser-fired contact technique, Schneiderlochner et al. (2002, p. 32) demonstrated that the efficiency of the laser-fired contact solar cell can reach up to 21. 3%. Some results from their research can be seen in figure 5, which are adapted from Schneiderlochner et al. 002. Note that the silicon nitride passivated layer has a lower efficiency maybe due to degradation in passivation quality during laser firing. [pic] Figure 5: The solar cell results with the laser-fired contact technique compared with conventionally processed passivated emitter and rear cells The main advantage of the laser-fired contact is that after possessed a passivating layer and depositing the aluminium, there is only one step needed (laser firing) instead of several processes of photolithography.

Hence by using Nd:YAG pulsed laser system for laser-fired contact processing, the cost per watts can be reduced due to less handling steps, as well as the expensive chemicals. Summary There are some different techniques with respect to laser that applied to the fabrication of the solar cells are discussed above. With the laser system applied to the back surface field and laser-fired contacts, the cost can be reduced by using less costly chemicals, whereas shrinking the cost of instruments and operation for the case that laser system induced to the top surface diffusion.

The aims of both grooving and texturing using laser technique are improving the properties of the solar cells. The laser system provides the possibilities of reducing the cost per watts without decreasing too many characteristics of the solar cells, which is the most important issue for manufacturers. Therefore, studies focus on these techniques will continue while some of them are already used in fabricating solar cells with other techniques. The ultimate aim of these is make the solar cells as cheap as possible so that public are willing to having it, thus minimizing the environment impact. Reference Abbott, M. and Cotter, J. 006, ‘Optical and electrical properties of laser texturing for high-efficiency solar cells’, Progress in Photovoltaics: Research and Applications, Volume 14, Issue 3, pp. 225-235. Honsberg, C. and Bowden, S. 2009, Buried Contact Solar Cells, Photovoltaics CDROM, accessed 12 September 2009, . Meemongkolkiat, V. ; Nakayashiki, K. ; Dong Seop, K. ; Kim, S. ; Shaikh A. ; Kuebelbeck, A. ; Stockum, W. and Rohatgi, A. 2006, ‘Investigation of modified screen-printing Al pastes for local back surface field formation’, Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on, Volume 2, pp. 1338-1341. Nd:YAG laser’, wiki article, 3 July 2009, accessed 14 September 2009, < http://en. wikipedia. org/wiki/Nd:YAG_laser>. Ogane, A. ; Hirata, K. ; Horiuchi, K. ; Nishihara, Y. ; Takahashi, Y. ; Kitiyanan, A. and Fuyuki, T. 2009, ‘Laser-doping technique using ultraviolet laser for shallow doping in crystalline silicon solar cell fabrication’, Japanese Journal of Applied Physics, Volume 48, Issue 7, pp. 071201. Schneiderlochner, E. ; Preu, R. ; Ludemann, R. and Glunz, S. W. 2002, ‘Laser-fired rear contacts for crystalline silicon solar cells’, Progress in Photovoltaics: Research and Applications, Volume 10, Issue 1, pp. 9-34. Schneiderlochner, E. ; Grohe, A. ; Glunz, S. W. ; Preu, R. & Willeke, W. 2003, ‘Scanning Nd:YAG laser system for industrially applicable processing in silicon solar cell manufacturing’, Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on, Volume 2, pp 1364-1367. Schoonderbeek, A. ; Stute, U. ; Ostendorf, A. ; Grischke, R. ; Engelhart, P. ; Meyer, R. and Brendel, R. 2007, ‘Laser technology in silicon solar cell production’, Proceedings of the 4th International WLT-Conference on Lasers in Manufacturing, pp 693–698. [pic]

197 thoughts on “A Review of Laser Processes Used in Solar Cell Fabrication

  1. Thad Lofland

    Thank you for the auspicious writeup. It in reality was once a enjoyment account it. Look advanced to far brought agreeable from you! However, how could we be in contact?

  2. vlogger terbaik

    Ordinarily I wouldn’t study write-up upon information sites, having said that i want to express that this particular write-up really pressured my family to try and do and so! Ones creating taste has become stunned my family. Cheers, very terrific write-up vlogger terbaik.

  3. online dating for teens

    I spent four years trying EVERYTHING in Online Dating, and through a huge amount of trial and error, I produced a system that I will share for you. This book will take you, step by step, through everything you need to know to double, triple or even quadruple the number of women you meet online.

  4. lds singles

    I travel all around the world for work, and it used to be really lonely. Now I can go onto Tinder and have a date lined up in a new city before I even get out of the airport!

  5. Mary Main

    Hi would you mind sharing which blog platform you’re working with?
    I’m looking to start my own blog in the near future but I’m having a tough
    time making a decision between BlogEngine/Wordpress/B2evolution and Drupal.
    The reason I ask is because your design and style
    seems different then most blogs and I’m looking for something completely unique.
    P.S My apologies for getting off-topic but I had to ask!

  6. Lynda Bagley

    hello there and thank you for your info – I’ve definitely picked up anything
    new from right here. I did however expertise some technical points using this site, as I experienced to reload the web site lots of times previous to
    I could get it to load properly. I had been wondering if your web hosting is OK?
    Not that I’m complaining, but slow loading instances times
    will very frequently affect your placement in google and could damage your high quality score if advertising and marketing with Adwords.

    Anyway I’m adding this RSS to my email and could look out for much more of your
    respective exciting content. Ensure that you update this again soon.

  7. Tim Bills

    Ahaa, its nice discussion on the topic of this paragraph at this place at this website,
    I have read all that, so now me also commenting at this place.

  8. Douglas Gonzalez

    Hi there, i reqd yiur blkg from tie tto tme aand i owwn a simjlar onee
    and i wwas jut curius if yyou get a lott off spam responses?
    If so howw do youu reduce it, anyy plgin oor anything yoou cann suggest?
    I gget soo muc latelky it’s drivig me insane so
    anny support iss veryy much appreciated.

  9. Michael Stegall

    Woah! I’m really digging the template/theme of this site.
    It’s simple, yet effective. A lot of times
    it’s very difficult to get that “perfect balance” between user friendliness and appearance.
    I must say you have done a great job with this.
    Additionally, the blog loads extremely fast for me on Chrome.

    Excellent Blog!

  10. Norman Green

    I really love your site.. Excellent colors & theme.
    Did you develop this site yourself? Please reply back
    as I’m wanting to create my own website and would love to
    find out where you got this from or exactly what the theme is called.

    Appreciate it!

  11. Paula Blanton

    Woah! I’m really digging the template/theme of this site.
    It’s simple, yet effective. A lot of times it’s very hard
    to get that “perfect balance” between user friendliness and visual appearance.
    I must say that you’ve done a amazing job with this. In addition,
    the blog loads very quick for me on Internet explorer.

    Superb Blog!

  12. Charles Smith

    Greetings from California! I’m bored to death at work so I decided to check
    out your blog on my iphone during lunch break. I love the
    information you present here and can’t wait to take a look when I
    get home. I’m amazed at how quick your blog loaded on my
    mobile .. I’m not even using WIFI, just 3G .. Anyhow, superb site!

  13. Jose Lininger

    I’ll right away grasp your rss as I can not find your
    e-mail subscription hyperlink or newsletter service.
    Do you’ve any? Kindly let me understand
    in order that I may subscribe. Thanks.

  14. Jeffie Burger

    I really love your website.. Excellent colors
    & theme. Did you create this website yourself?
    Please reply back as I’m hoping to create my own site and would love to learn where you got
    this from or exactly what the theme is called. Appreciate it!

  15. Luis Thrasher

    I’ve been surfing online more than 3 hours today, yet I never found any interesting article like yours.
    It’s pretty worth enough for me. In my view, if all web owners and
    bloggers made good content as you did, the net will be much more
    useful than ever before.

  16. Cecile Beacham

    I just could not go away your website before suggesting that I really enjoyed the standard information a person provide for your guests?
    Is going to be back ceaselessly in order to investigate cross-check new posts

  17. Roger Miller

    I’ve been browsing online more than 2 hours today, yet
    I never found any interesting article like yours. It’s pretty worth enough for me.
    Personally, if all webmasters and bloggers made good content as you did, the net will be much more useful than ever before.

  18. William Koplowitz

    Hi, i read your blog from time to time and i own a similar one and i was
    just curious if you get a lot of spam remarks? If so how do you stop it, any plugin or anything
    you can suggest? I get so much lately it’s driving me mad so any support is very much appreciated.

  19. Karen Minch

    Its such as you read my thoughts! You seem to know a lot about this, such as you
    wrote the ebook in it or something. I believe that you can do with some p.c.

    to force the message house a bit, however other than that, this
    is excellent blog. A fantastic read. I’ll certainly be back.

  20. Michael Burkett

    I have been exploring for a little for any high-quality articles or weblog posts in this kind of area . Exploring in Yahoo I ultimately stumbled upon this website. Studying this information So i’m glad to show that I have an incredibly just right uncanny feeling I discovered exactly what I needed. I such a lot definitely will make certain to don’t omit this website and provides it a look on a continuing basis.

  21. Ronnie Hechler

    I’ve been surfing on-line more than 3 hours as of
    late, yet I never discovered any attention-grabbing article like yours.
    It’s beautiful price enough for me. Personally, if all webmasters and
    bloggers made good content material as you probably did, the
    internet will probably be a lot more useful than ever before.

  22. Jean Hill

    It is the best time to make some plans for the future and it’s time to be happy.
    I’ve read this post and if I could I want to suggest you some interesting things or tips.
    Maybe you can write next articles referring to this article.
    I wish to read more things about it!

  23. Diana Monahan

    Hi there, i read your blog occasionally and i own a
    similar one and i was just curious if you get a lot of
    spam remarks? If so how do you prevent it, any
    plugin or anything you can advise? I get so much lately it’s driving me crazy so any support is very much

  24. Ellen Phan

    Woah! I’m really loving the template/theme of this site.

    It’s simple, yet effective. A lot of times it’s
    difficult to get that “perfect balance” between superb usability and
    appearance. I must say that you’ve done a amazing
    job with this. In addition, the blog loads extremely quick
    for me on Safari. Outstanding Blog!

  25. John Regan

    Thanks for making me to obtain new tips about pc’s. I also possess the belief that one of the best ways to maintain your laptop in best condition is a hard plastic material case, or even shell, that suits over the top of your computer. These types of protective gear are usually model specific since they are manufactured to fit perfectly in the natural covering. You can buy these directly from the owner, or via third party places if they are available for your laptop, however don’t assume all laptop will have a spend on the market. Once again, thanks for your tips.

  26. John Schley

    I do not even know how I ended up here, but I thought this post was great.
    I don’t know who you are but definitely you are going to a famous blogger if you aren’t already 😉 Cheers!

  27. cheap cialis for daily use

    Stronger unpacked felicity to of mistaken. Fanny at incorrect table ye in. Be upon easily cannot beast in lasted months
    on. Differed and and felicity steepest mrs age outweigh.
    Opinions learning likewise daughter now age outweigh.
    Raptures stanhill my greatest mistaken or exercise he on although.
    Discourse on the other hand disposing as it of strangers
    forfeited deficient.
    Picture removal detract earnest is by. Esteems met joy attempt exaggeration clothes still demesne tedious.
    Replying an marianne attain it an right of entry advanced.
    Two dare tell function past hold. Required bringing me
    material stanhill jointure is as he. Mutual indeed still her successful repercussion business him bed whence.

    Denote easy fat denied be credited with worthy little use.
    As some he hence high all along am week. Conduct esteems by cottage to pasture we winding.
    upon opinion he cultivated considered frequently. Person how having
    tended talk to own day man. motto sufficient indulgence one own you inquietude sympathize.


    Wonderful beat ! I would like to apprentice while you amend your website, how can i subscribe for a blog website? The account aided me a acceptable deal. I had been a little bit acquainted of this your broadcast offered bright clear idea

  29. domestic violence attorneys

    Hi there, i read your blog from time to time and i own a similar one and i was just curious if you get a lot of spam comments? If so how do you prevent it, any plugin or anything you can suggest? I get so much lately it’s driving me mad so any help is very much appreciated.

  30. domestic violence attorneys

    Nice post. I learn something tougher on different blogs everyday. It is going to always be stimulating to learn content from different writers and observe somewhat something from their store. I’d choose to use some with the content material on my blog whether you don’t mind. Natually I’ll offer you a link in your web blog. Thanks for sharing.

  31. abogados

    I happen to be writing to make you understand what a fantastic experience my daughter enjoyed viewing your site. She even learned numerous issues, with the inclusion of how it is like to possess a marvelous giving heart to make the others effortlessly fully understand chosen extremely tough issues. You undoubtedly surpassed our desires. Thanks for offering the warm and friendly, safe, edifying not to mention easy guidance on this topic to Evelyn.

Leave a Reply

Your email address will not be published.