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Solar cells and tunnel diodes on Ebay..

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Conundrum

Tue Jun 08 2010, 08:13PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

heh... reckon these are worth getting as a group buy? i notice that they are US shipping only, sadly.

for that price even if only 2/3 work well they are useful.

-A

...

Tue Jun 08 2010, 11:02PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I am surprised those cells are available on ebay, the solar cell manufactures are usually quite careful with the cells they scrap (my guess is they walked off in a pocket--would explain the US only shipping). In any case, those are dual junction cells (there is a germanium cell on the bottom, and a GaAs cell on top, both sensitive to different wavelengths- it should be about 20-25% efficient if it met spec at any point in its life), and cost about $300 a piece when sold through the proper channels. Regardless, they blow the pants off normal silicon cells any day!

MinorityCarrier

Tue Jun 08 2010, 11:42PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

The discoloration in the photo suggests the topside passivation is delaminating, allowing the anode metalization (aluminum?) to corrode.

Gallium arsenide is extremely brittle, the comment about being designed to survive impacts from space derbris makes little sense.

A few years ago Spectrolab use to routinely sell on-line, batches of GAs solar cells that failed to make the efficiency grade for satellites.

Conundrum

Wed Jun 09 2010, 05:26PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

hmm..

reckon they are useable?
i worked out that using uv methacrylate adhesive(relatively cheap, and sold for optical repair etc) could be used to capillary seal these, as most of the damage is near the edges.

at this price its well worth someone taking the plunge then selling them ten at a time to 4hv'ers.

i'd be happy to pay $50 + shipping for a handful of them so we only need to get another four people to take a chance on them and it becomes a simple matter of a group buy.

the last item i bought like this (box of "broken" 9V ultralife batteries) contained something like 75% perfectly good pp3 lithiums which I am still using...

-A

btw check out

wylie

Thu Jun 10 2010, 03:50AM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

at this price its well worth someone taking the plunge then selling them ten at a time to 4hv'ers.

You're our man. You've got the ideas to make them work and you found the link. See what you can do, and THEN people might lay down some money.

(Still waiting for synthetic photosynthesis. Is that wording redundant?)

IntraWinding

Thu Jun 10 2010, 06:10AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Check out the sellers 'Completed Listings'. He's recently sold 3 batches of these cells for much less than the current price. One batch of 100 went for $85! So it might be worth waiting.

I wonder how they got so messed up?

Proud Mary

Thu Jun 10 2010, 08:55AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The tunnel diodes look interesting, Andre.

Tunnel diodes are quite hard - radiation resistant - compared with other diodes species, and so were manufactured in quantity in the former USSR.

Conundrum

Thu Jun 10 2010, 07:29PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

cool...

sadly no spare cash atm, and as i said the listing is US only.

i did purchase some of those diodes so if someone wants a few let me know..

-A

UltraMagnus

Fri Jun 11 2010, 09:21AM

Registered Member #2875 Joined: Mon May 24 2010, 08:28AM
Location: England
Posts: 42

so, other than making electronics for your nuclear bunker, what use is a tunnel diode? they don't look like they can take much voltage or current by his specifications.

his specifications are weird though, what is a "mkA"? millikiloamp?

Proud Mary

Fri Jun 11 2010, 11:03AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

UltraMagnus wrote ...

so, other than making electronics for your nuclear bunker, what use is a tunnel diode? they don't look like they can take much voltage or current by his specifications.

his specifications are weird though, what is a "mkA"? millikiloamp?

You can use tunnel diodes wherever a two-terminal negative resistance device would be helpful, but their strength lies in their ability to work as microwave amplifier, mixer, and oscillator, usually within the SHF part of the spectrum.

They are low power devices, but who can say what point-to-point distances could be bridged on a clear day with 100mW worth of 24GHz, and compact, very efficient parabolics mounted on camera tripods. Sounds fun to me.

mka = uA.

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