# Conductive Glass

1. ### mrjeffy321

881
I would like to make some conductive, transparent, glass by somehow applying a thin layer of something [SnO2] to one side of a glass plate.

I have seen this set of instructions,
http://www.teralab.co.uk/Experiments/Conductive_Glass/Conductive_Glass_Page1.htm
Which describes heating some Tin (II) Chloride on a sheet of glass with a hot plate which vaporizes the power and deposits a layer of SnO2 on the glass surface. Although the procedure looks simple enough, the idea of having Tin vapor does not sound very appealing to me.

It probably would be far easier to simply buy the glass from a manufacturer, but I have only found a small number of suppliers who sell it, and it is not very easy to get a price quote.

My goal is the build a photovoltaic cell similar to the one described here,
http://www.solideas.com/solrcell/english.html
One of the critical components is conductive glass; I should be able to handle all the other materials.

2. ### Gokul43201

11,044
Staff Emeritus
How about saliva ?

Did you look for distributors of ITO glass ? I just did - they're all in Asia or Europe !! Every single one !

If you haven't already, give it a look...there may be something I missed.

Last edited: May 21, 2006
3. ### mrjeffy321

881
I did not search indepth for a specific type of conductive coating on the glass as that does not matter so much to me.

I have seen distributors who are said to be located in the US (I think there might be one in California), but the problem I am probably going to have with any distributor is that no one is going to want to sell to me (a one time, small purchase, individual).
I dont even know what the price range is that we are talking about, whether it is $.10 per square inch or$100 per square inch will greatly effect my decision to make it.
I have seen "kits" to build this type of solar cell which [I am pretty sure] include a small square of this glass, but these kits sell for around $70 I think, if that is any indicator of the price of the glass (TiO2, I-, graphite, is all cheap). 4. ### Danger 9,663 Mrjeffy, try contacting some security companies in your area. Back when I was a locksmith, with training in alarms, there was a liquid that you could paint onto windows instead of using the foil strips to detect glass breakage. It was almost completely transparent and electrically conductive. In some ways, it was very much like varnish or shellac. Unfortunately, I can't remember the name of it. 5. ### Bystander 4,077 Edmund Scientific, Newport (Newport-Oriel-Spectra-Physics) --- figure on not too outrageous minimums at Newport. Whether they got whatcha want's another question --- anyone peddling windows, lenses, and coating services oughta be able to take care of you. 6. ### mrjeffy321 881 Danger, from your description, the stuff you speak of sounds very promising as a solution. I did email one security company today who replied back saying that the method I [you] were describing was outdated and seldom used now-a-days, although I dont think he understood what I was saying since he refered to it a "window foiling". I will call come glas and security companies tomorrow. I did not see anything like what I am talking about at Edmund Scientific. Perhaps I missed it, or were just suggesting to look there? 7. ### Danger 9,663 Yeah, it's definitely outdated. These days, almost all alarms are motion sensor based, perhaps with a Shatterguard for windows (that's an accoustic pick-up tuned to the sound of glass breaking). The fellow who responded to you probably did understand. The conductive liquid was used in place of aluminum foil for discreet applications, so use of the term 'foiling' is appropriate for both. I was hoping that there might be some kicking around on some company's back shelf from the old days. 8. ### Gokul43201 11,044 Staff Emeritus There are two kinds of folks that make/sell conductive glass - the electronics/semiconductor folks, and the window making people. The product from the former group will likely be high quality stuff that's very expensive. PS : I specifically named ITO (Indium Tin Oxide) glass, because that's the only conductive glass coating I was aware of, and had imagined that it was the most popular. Maybe that's not true. 9. ### mrjeffy321 881 I called a few glass companies today. Some of them thought I was totally crazy, one inparticular was quite helpful. I had two seperate people recommend a type of glass called "Low E" glass. There is a thin, slightly colored, metalic coating on the glass which allows it to conduct electricity [so says 2 out of people who knew about it]. The problem is that, one, the electrical coating is delicate and is not meant to be exposed to the elements. This is OK however, since the conductive side should be protect within the cell. The second problem is that the glass's coating is specialy engineered to reflect heat and ultraviolet rays. This might pose a problem as far as gathering light from the sun for the cell to run off of. I am not sure exactly what wavelength's the metalic coating reflects (I'll try to look that up online) or what wavelength's the solar cell will generate a current from, but this might work. There are suppose to be a couple different color options for the coating. Although if you hold the glass up to the light and loko through, the color should not be easily noticble, but if you put it on a white peice of paper, you might be able to see a light brown/green, gray, or bluish tint. The glass guy said that this "Low E" glass is pretty common now-a-days for contrustion of new homes since it keeps out heat and UV rays so well. The price is not bad either. One person quoted me a price of roughly$12.00 to $14.00 per square foot, another person said about$4 per ft^2 of 1/8" glass. I dont know how this compared to other types of glass, but it does fall within my budget.
They dont keep it in stock, but they have samples which I will try to go down and see when I get a chance.

Another type of glass which wa suggested was called "Solor Cooled Bronze" which is said to be used often in high rise buildings and such. It is suppose to conduct electricity and is more durable than the "Low E", but is also much less transparent. I was told that although, "you can see through it, it isnt easy".

The Low E glass looks promising.

10. ### Paula

36
You left us hanging what the coducive stuff is.

11. ### mrjeffy321

881
I am not exactly sure what they use on the Low E glass to make it conductive, all I have seen on the internet is that they use either a very thin coating of metal or metalic oxide.
I suspect it is either a THIN Titanium (IV) Oxide or Tin (IV) Oxide made in a similar fashion as described by the method linked to in my first post. Perhaps the use of different metals or their oxides is what gives the different colors mentioned (then again, it at the scale of the coating, it could also have something to do with diffraction too).

As Gokul43201, ITO (Indium Tin Oxide) coated glass is a very popular type. I see the glass coating desribed as ITO on all the higher quality glass which is advertised for such a purpose. Perhaps this 'Low E' glass is the same thing, or perhaps it is just a coincidence that it happens to conduct since its actual purpose is to keep heat in/out (trap it inside during the winter, reflect it away in summer).

12. ### Gokul43201

11,044
Staff Emeritus
jeff, I think a soft-coat double-glazed argon filled low-E glass with high solar gain will work for you. And when you find someone that can sell you some, confirm what the coating material and thickness are.

Low-E (for low emittance)glass is different from ITO glass...but may also work reasonably. Typical transmission coefficients (for visible wavelengths) in the high solar gain category are about 70 to 75%. Is that okay for you ?

PS : What is your solar cell made of ? (ie: what semiconductor makes up your photodiode ?)

13. ### Gokul43201

11,044
Staff Emeritus
Ignore tha above post. I just read your solar cell link. The double-glazed soft coat will not work. The metal layer (usually silver) is on the inside of a two pane glass with argon filling the gap between the panes to prevent oxidation of the silver.

A hard coat glass, however, might work. Hard coats are often metallic tin, and are applied to one surface of a single pane (I think).

Another problem with low-E glass is the terrible tramsmissivity in the UV and IR regimes. If I understood better how your solar cell works (I read the link in the OP and couldn't make much sense of it), I might be able to judge whether this may be a problem. Also, there's something about a TiO2 layer. Have you got that part of it covered ?

14. ### mrjeffy321

881
I am fine with a 70% transmittance at this point, When the solar energy to electricty conversion efficiency is only about .5% to 1% anyway [statistic from the above linked web site], we are not talking a huge energy loss. I will worry about tweaking the output up higher later.

I am not sure how the loss of any UV or IR waves will effect the cells preformance. I think IR waves are blocked anyway through most/all types of glass, so this probably isnt a problem. But the lack of UV rays might be significant.
From this site,
http://www.physics.udel.edu/~ismat/nirtresearch.htm
I think I might have read on some web site I can no longer find that the dye is used to better absorb the light instead of relying purely on the TiO2.
From this site,
http://www.spie.org/web/oer/august/solar_tech.html
I have seen several diagrams [and web pages] describing this type of solar cell, many of which go so far as to label the conducting layer on the glass as SnO2:F.

As for the TiO2 layer, I think I have that covered. I just happened to already have a bunch of TiO2 sitting around, and I think I should be able to follow these instructions closely enough,
http://www.solideas.com/solrcell/coatglas.html
My only concerns would be about the purity of my TiO2 supply and to get the powder particles finely ground enough (it is already pretty fine, hopefully it will be enough).

Another site's instructions,
http://www.chymist.com/TiO2 Raspberry Solar Cell.pdf
Same instructions, but with videos,
http://mrsec.wisc.edu/Edetc/nanolab/TiO2/

4,077

9,663
17. ### mrjeffy321

881
I have been away for a couple days, but that is not to say that I did not make any progress on the conductive glass.

I could not find anyone near enough to where I live that would sell me a plain sheet of Low-E glass since it is a "soft coat glass" which is easily damaged , however, one person did go so far as to call up their distributer and find a substitute.
I think the substitute glass is called "sun beam 500" or something to that effect (I thought I had it written down, but appearently not). And get this, it was free, the guy said it was just a sample peice and gave it to me.
Actually, when I look at the label/sticker on the glass sample, it does say "Low E" on it as the glass type, so maybe I got the kind of glass I was shooting for any way.

When you hold the glass up to the light, it looks just like any other glass, clear. But if you put it infront of a white peice of paper, you can see it has a slight tint to it. When I multilayer it, after about 9 or 10 layers, it get pretty dark.

The peice of glass I got was originally 1 square foot (1' x 1'), but I need at least two peices in order to actually use it. Just because the glass company gave me the glass for free doesnt mean they will cut it for me too, they wanted $7.00 per cut, so instead I went out a bought a$4 glass cutter. Even though I had no idea what I was doing, I think I managed to cut the glass pretty well (save a few accidents) into 3"x3" squares.

The glass, obviously, does conduct electricity on one side.
Using the resistance meter on a multimeter (which I dont trust for accuracy), I measured the resistance between the two probes seperated by 12 inches to be about 150 ohms. Measuring the resistance using Ohms Law, a volt meter and an amp meter, I got a more believeable reading of about 90 ohms (probes still seperated by 12 inches).

I havent went any further then cutting the glass right now as far as constructing the solar cell, but seeing how that really isnt the true topic of the thread, I think that pretty much wraps things up.

18. ### Bystander

4,077
Too late to help you now, but for future reference: single scratch w' glass cutter; moisten the scratch w' spit, water on a Qtip, something; thumbs on scratched side, fingers spread out on back side, both hands, either side of "cut;" pull while applying pressure w' fingertips to "bend" the glass as if it were hinged at the scratch.

Don't ask me what the wetting does to help the crack propagate from the scratch (surface tension effect is my best guess, don't really know anything), but it works.

19. ### Danger

9,663
Might be a hydraulic effect, Bystander. I don't know for sure, of course, but I suspect that the water gets drawn into micro-fissures by capillary action and 'wedges' them along. It would be interesting to find out from someone who knows more about it.

20. ### mrjeffy321

881
I had a small sheet of glass sitting around which I used to practice on before I did the real thing on the good glass. The practice glass is/was about 1/16 inches thick, half the thickness of the good glass, but even with glass this thin, I never got very good at doing large cuts. I could so all right when it came to 1” or 2” segments on the end of a long narrow piece, but for instance, cutting it in half was almost sure to fail. I was using vegetable oil and water to lubricate and moisten the glass as I was trying to cut it as deep as possible.
I don’t think there is any way just a single scratch with a glass cutter would have cut that 1/8” glass (at least for me).
But now I have plenty of small “practice” pieces of glass in addition to the few good squares I did cut.

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