Making Conductive Glass for Photovoltaic Cell | Tin (II) Chloride Method

[mrjeffy321]

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.

 

[Gokul43201]

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

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.

 

[mrjeffy321]

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 don't 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).

 

[Danger]

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.

 

[Bystander]

Edmund Scientific, Newport (Newport-Oriel-Spectra-Physics) --- figure on not too outrageous minimums at Newport. Whether they got what are you want's another question --- anyone peddling windows, lenses, and coating services oughta be able to take care of you.

 

[mrjeffy321]

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 don't think he understood what I was saying since he referred 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?

 

[Danger]

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.

 

[Gokul43201]

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.

 

[mrjeffy321]

I called a few glass companies today. Some of them thought I was totally crazy, one inparticular was quite helpful.

I had two separate 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 piece 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 don't know how this compared to other types of glass, but it does fall within my budget.
They don't 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 isn't easy".

The Low E glass looks promising.

 

[Paula]

You left us hanging what the coducive stuff is.

 

[mrjeffy321]

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).

 

[Gokul43201]

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 ?)

 

[Gokul43201]

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 ?

 

[mrjeffy321]

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 isn't a problem. But the lack of UV rays might be significant.
From this site,
http://www.physics.udel.edu/~ismat/nirtresearch.htm

TiO2 is a large bandgap semiconductor (~3.2 eV) and its absorption edge is in ultraviolet (UV), which is only 5-8% of the solar light. This absorption edge needs to be extended to the visible range to make it useful for the applications in which involves all the sunlight.

I think I might have read on some website 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

In the nanocrystalline cell, the colloidal TiO2 becomes photosensitized when the light excites the Ru-dye, which then donates an electron to the porous TiO2. From there, the electron travels through the electrode to a load (i.e., a motor or battery) and to the counter electrode.
[...]
The TiO2 is one of the few semiconductors which is stable in a photoelectrochemical cell. However, it has a band gap of 3.1 eV and, like the silver halide, is therefore insensitive to visible light.

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/

 

[Bystander]

http://www.abrisa.com/Guide/GlareReduction/antiReflective/AR_sputter_Desc.asp

http://www.freepatentsonline.com/6291074.html

http://www.freepatentsonline.com/6291074.html

--- and, lots more --- googel "reflecting glass"+"sputtering" and you'll get plenty of information.

Yeah, Edmund seems to have turned into more a "toy store" than a cheap source for anything useful.

 

[Danger]

I'm not sure how helpful it'll be, but I found this: http://www.powersourcing.com/sf/transparentconductivecoating.htm"

 

[mrjeffy321]

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 piece 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 piece 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 piece 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 doesn't 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 don't trust for accuracy), I measured the resistance between the two probes separated 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 separated by 12 inches).

I haven't went any further then cutting the glass right now as far as constructing the solar cell, but seeing how that really isn't the true topic of the thread, I think that pretty much wraps things up.

 

[Bystander]

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.

 

[Danger]

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.

 

[mrjeffy321]

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.

 

[Gokul43201]

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.

Ask Gurney, Orowan and Wiederhorn.

The effect is actually thermodynamics and diffusion related, rather than hydraulic. Crack propagation speeds in glasses are strong function of surface energies. The presence of water reduces the activation hump for one of the steps in the propogation process. So, during this phase of the propagation, the crack growth is rate limited by the diffusion of water to the crack tip. The greater is the crack propagation velocity, the lower is the probability for the crack to sample low energy paths that are not directly in front of it (ie: the propagation is more removed from equilibrium conditions).

References:

E. Orowan, The Fatigue of Glass Under Stress, Nature 154, 341-343 (1944).

C. Gurney, Delayed Fracture in Glass, Proc. Phys. Soc., London 59, 169-185 (1947).

S. M. Wiederhorn, S. W. Freiman, E. R. Fuller, Jr., and C. J. Simmons, Effects of Water and Other Dielectrics on Crack Growth, J. Mater. Sci. 17, 3460-3478 (1982).

 

[Danger]

Awesome, Gokul. Thanks for the info.

 

[mrjeffy321]

I have been contacted by members regarding my success in constructing one of these solar cells described earlier in the thread, so I thought I would post the results for those interested (either now or in the future).
I was able to successfully build several cells and get measurable electrical output from them using the conductive glass earlier described. In full, June, sunlight, I was able to measure a voltage of between .05 and .08 volts…not a lot, but it counts. I was never able to measure any current from the cell, probably since my cells were too small and the internal resistance on the glass was too great. When dying the TiO2, make sure to use real raspberries / raspberry juice / …, (I first tried using some [what I later found to be] artificial raspberry jelly which did not work). Although the instructs on constructing these cells says to wait to dye the TiO2 until after you have adhered it to the glass, I found it was easier to simply place some raspberry juice in with my TiO2 and water suspension, essentially pre-dying it, then painting it onto the glass with an ear swab and evening it out with a plastic straw and some scotch tape. Almost certainly, the TiO2 I was using was no where near nanoparticle size and this likely greatly affected my results.


Friday, we had a physics colloquium at my school on these very same photovoltaic cells. I had no idea this stuff was so cutting edge, even the one I built in my kitchen is essentially the same thing all these guys are doing research on (from what I heard, lots of interest in it in Japan [by Toyota]).
I really wish I would have brought something to write with to the presentation, but I did find out the answer to a few of the questions which were asked earlier. A lot of this is just going to chunks of info I am remembering, so excuse how terribly random all of it is put together.

It seems that these dye sensitized photovoltaic cells can theoretically get quite high efficiencies, somewhere around 90% I think (from what I could see on the graphs). Although they are experimenting with all different types of dyes and electrolytes, usually the highest efficiency is around the 500 nm wavelength of light, but all across the visible spectrum they can get fairly good results. What they are trying to do is get it so that they can absorb all the light from about 1.4 eV and down.
They are designing the cells / panels to last 20 years (100,000 “cycles”, I think) or so, so as to compete with the warranties of the regular silicon based solar cells.
Although the Iodide electrolyte is commonly used, they are trying to develop other, ionic liquid electrolytes as well as even solid / “gelled” electrolytes for use in the cell.
They are also coloring the cells a wide range of colors….one interesting picture was of a “plant” made with green colored solar cell “leaves” which absorbed the light shown on them and powered these butterfly things as a demo.
They can also made the cells very transparent (as well as colored)…almost like tinted / stained glass, you can still see through it to a good degree, but it also generates electrical energy. Also, making the cells flexible is a big deal too.
Another advantage of this dye synthesized cell compared to a silicon cell is that the electrons “live” longer after being released by the dye. If the electrons are not conducted away from the cell fast enough, they stand the chance of being reabsorbed and not doing any work. In a silicon cell, this happens very quickly, but in this cell, the re-absorption process takes longer so you can thicker coatings to use to absorb light.
I think he said that in China, they are able to produce these cells for about $1.00 per watt….but he also added that in China, their cost of labor is much less than in other places. The majority of the cost of the cell (over half) is in the conductive glass. They use a type of conductive glass with a resistance of about 1 ohm per square.

Here is the “poster” for the event,
http://www.utdallas.edu/physics/lectures/info/Fall2006/Graetzel/Graetzel%20poster%20150px.jpg

 

[Cesium]

This is quite elaborate I must say. When I was building a hydrogen fuel cell, I had to be content with <0.5 volts as well. It's just nice to know that the process is working to some extent regardless of effiency.

The only solar cell I've built is the old fashioned cuprous oxide cell. I would like to some day try this dye-based one out, but I have no SnO2 or any source of tin for that matter aside from solder or bronze perhaps.

 

[NoTime]

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.

I've cut quite a bit of glass.
Some cuts 8 feet long.
Never make more than one pass with the cutter.
There is however, a certain amount of skill involved in learning to press hard enough so that the scratch is continuous. You can patch up the missed spots but success goes way down.
When doing the actual break, press on the edge perpendicular to the scratch.
Don't try pressing on the parallel edge. It never works.
For small pieces a nail aligned with the start of the scratch lifts the edge enough to do the break. For long cuts I align the scratch on a staight edge.
Thickness doesn't seem to matter except how hard you have to press.
Wear safety glasses. You always find sparkleies around after cutting glass.

Never heard of the water bit.
Seems to cut just fine without it.

 

[Darryl]

ITO glass is commonly (or commercially called) LOW E glass. i know Pilkington sells a LOW E glass, (filters IR light), spectrically selective but clear glass, but is condustive due to the indium-tin oxide coating, (on one side only, from memory).

and can be purchased in window size, and different thickness.

the other option is to manufacture your own ITO mixture, (with silicone), menicsus dip it, (extraction speed determines coating thickness, both sides). then refire the glass to fire the ITO coating.

 

[physics girl phd]

I know there are comanies in the US that make ITO coatings -- a google search gave this one:
Thin-Films Research, Inc. - Westford, MA -- http://www.thinfilmsresearch.com
I found an APS paper that referenced a "Donnely Applied Film Corps, Boulder, CO".

Some others are listed here: http://www.thomasnet.com/products/coatings-thin-film-16000697-1.html

I think I've looked into this before and coating runs usually have some minimun order around US $1k-2k.

 

[jd1101]

DSSCs

Hey Jeff,

I've been working on this project for almost three years now at Washington State University. There are many suppliers of ITO conductive glass. We've made lots of progress on these Dye Sensitized Solar Cells (DSSCs) and follow all the scientific publications on it. It turns out almost every part of the DSSC has the potential for changing the amount of power dramatically.

The biggest example to date is the way you prepare the TiO2 paste. We make paste using a method that involves stirring the TiO2 powder in different solvents (water, alcohol, etc) and each solvent morphs the surface of the TiO2 differently s.t. the dyes will interact with the TiO2 differently (attach stronger, inject electrons more easily, be less sensitive to contaminants, etc). Most methods require a surfactant of some kind (soap usually) that is burned off in a baking step, however we've found that if you for-go the soap and stir long enough (we stir in ethanol for two weeks using a stir plate and magnetic bar) you can deposit a film with the same consistancy that doesn't require baking, with the one major draw-back that you lose about 10-30% of the power.

We are interested in natural dyes, i.e. dyes you can get from plants. We've found there is a major step in separating the dyes you want from the rest of the materials in plants, and most dyes are easily degraded. There are ways of getting around the degradation (nature's little secrets), but they can be very tricky. TiO2 is very well known as a degredation catalyst for organic molecules, which is why you have to "protect" the dye from the TiO2 (hint hint-sorry, can't give out all the secrets).

I'd be happy to answer any questions you may have by sending me an email to this username @wsu.edu

 

[Andreea]

I would like to know if there is another type of conductive glass... excepting the one coated with ITO..., I hope I am not out of topic. Thank you

 

[jd1101]

Conductive Layers

There are several variations on Tin Oxides (SnO2): Fluorine-doped SnO2 (FTO), Indium-doped SnO2 (ITO), and just SnO2. Each of these changes the Fermi-Level and conductivity of the conductive layer. Beyond these, I can't recall ever seeing any others.

 

[Andreea]

Thank you so much, for answering my question. Have you ever used transparent conductive glass before?

 

[jd1101]

Yeah, I use FTO just about everyday, and occasionally use ITO. The advantage to ITO is that it can be deposited on Temp-sensitive things, like plastic, or rather I believe this is so b/c I've never seen FTO on plastic. SnO2 is transparent in all it's mildly doped forms as deposited on glasses and plastics that I've used. I say "transparent", but in actuallity there is an internal reflection and index of refraction scattering that leads to ~4% loss of light, depending on the wavelength.

 

[Andreea]

Hi,
That's good to know... I would like to buy FTO coated glass... but it is kind of hard to find vendors... although I found out that I can buy it from Pilkington and AFG can you tell me your source?
Thank you very much

 

[Aaronnl]

Hello everyone,

dyesol sales conductive glass they have 10ohm square meter and 8ohm square meter.
I think this are good conductive glasses with attractive price.

have a look at https://secure.dyesol.com/index.php?template=TestCell