photovoltaic cell spectral sensitivity?

[Mark Fergerson]

I'm wondering what part of the spectrum most solar cells
(frinst those I salvage from cheapos calculators) are best
able to convert to current.

So I Google myself silly to little avail; most cells on
hand appear to be the single-crystal type, and near as I can
tell they digest near-IR best which is discouraging. I'm
assuming their visible appearance (many different colors) is
due to antireflection coatings rather than indicative of
their particular absorptive properties.

Anybody got a better set of Google terms that what I
thought were obvious, or maybe a decent website preferably
with some damn numbers?

TIA

Mark L. Fergerson

 

[Jonathan Kirwan]

On Mon, 18 Oct 2004 11:12:36 -0700, Mark Fergerson <nunya@biz.ness> wrote:

Anybody got a better set of Google terms that what I
thought were obvious, or maybe a decent website preferably
with some damn numbers?

I don't, right off the bat. But I would anticipate that the sensitivity would
be poorly controlled (in other words, some batches will behave differently than
other batches) in order to keep the whole process as cheap as reasonable and
that the overall response would be otherwise similar to the usual Si based lower
cost detectors you might find in a Hamamatsu catalog. Roughly speaking.

But I'll be interested to hear what you discover here.

Jon

 

[Nicholas O. Lindan]

"Mark Fergerson" <nunya@biz.ness> wrote

I'm wondering what part of the spectrum most solar cells
(frinst those I salvage from cheapos calculators) are best
able to convert to current.

So I Google myself silly to little avail; most cells on
hand appear to be the single-crystal type, and near as I can
tell they digest near-IR best

See, you found the data already.

which is discouraging.

You would be best off adjusting your needs and expectations,
you most likely aren't going to be able to change the properties
of Si.

assuming their visible appearance (many different colors) is
due to antireflection coatings

They have no antireflection coatings. Most are coated for humidity
protection. The color is part of the processing. The most efficient
cells are bright blue: that sort of says what color light they absorb,
ne'est ce pas?

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

[Mark Fergerson]

Nicholas O. Lindan wrote:

"Mark Fergerson" <nunya@biz.ness> wrote


I'm wondering what part of the spectrum most solar cells
(frinst those I salvage from cheapos calculators) are best
able to convert to current.

So I Google myself silly to little avail; most cells on
hand appear to be the single-crystal type, and near as I can
tell they digest near-IR best

See, you found the data already.

Well, poop.

which is discouraging.

You would be best off adjusting your needs and expectations,
you most likely aren't going to be able to change the properties
of Si.

That's not really the problem. In the fine tradition of
this group, I stated part of my needs without saying what
I'm trying to do. See, I plan to hide said scavenged cells
under simulated gemstones (don't ask why), and now I get to
find suitable fake stones that will pass enough NIR to be
worthwhile.

assuming their visible appearance (many different colors) is
due to antireflection coatings

They have no antireflection coatings. Most are coated for humidity
protection. The color is part of the processing. The most efficient
cells are bright blue: that sort of says what color light they absorb,
ne'est ce pas?

I've seen info that claims they are indeed AR coated, but
I see your point.

Thanks

Mark L. Fergerson

 

[Clarence]

"Nicholas O. Lindan" <see@sig.com> wrote in message
news:GDZcd.857$ta5.723@newsread3.news.atl.earthlink.net...

"Mark Fergerson" <nunya@biz.ness> wrote

See, I plan to hide said scavenged cells under simulated
gemstones (don't ask why), and now I get to
find suitable fake stones that will pass enough NIR to be
worthwhile.

Some minerals should pass IR very well. I know quartz does,
that should open up a whole range of colored quartzs. I have
a suspicion that garnet is also IR transparent. And diamond
certainly is.

There are lenses made of Germanium! They look gray in visible light, but work
as lenses for IR.

 

[Jonathan Kirwan]

On Tue, 19 Oct 2004 01:42:25 GMT, Rich Grise <rich@example.net> wrote:

Is quartz really IR transparent? I know it's one of very few items
transparent to UV.

A couple of things to keep in mind. Glass, the common form, is a combination of
quartz, soda (lowers melting point) and lime. Earlier, soda was hydrated sodium
carbonate with and lime and magnesia as mixed impurities. Today, it's sodium
oxide. Lime (quicklime) is calcium oxide and adding it keeps the resulting
glass from being water soluble, a problem that adding the soda creates. Fused
quartz (or silica) is a non-crystalline glass without the soda and lime stuff
added in. It's nice, pure SiO2, except it's the non-crystalline glass form.
(Ceria or titania (oxides) are also added to glasses and this reduces the short
wavelength side of the passband.)

Glass starts blocking around 380-400nm, I think, and (from actual measurements I
made some years ago) is pretty much opaque by the time you get to 310nm. But
there are differences in this, even in the garden variety 'green', 'brown' and
'clear' glasses used for various bottling needs. Much of the clear stuff, if
memory serves, passes some even at 320-330nm.

Even the better fused quartz (no impurities) has dropped to some 70%
transmission by 200nm and I don't think it goes much past 150nm. Often,
titanium dioxide is added to cut sharply anything shorter than 220nm or so. And
I think it starts dropping down on the long side at about 3.5 micron and is
quite dead before 5 microns.

Since UV contains wavelengths shorter than 100nm, I don't consider quartz to
really be a good, overall UV window -- unless all you like is the longer
wavelengths of it. For more UV transparency, sapphire works much, much better
and is available as windows, lightpipes, etc. (Diamond is just plain stunning
-- but then, diamond always seems to have a one-upsmanship going for it [best
heat conduction, best transparency bandpass, hardest, etc.])

Sapphire also has a much wider acceptance angle for lightpipes, about twice that
of quartz. That can be good or bad, depending on need, but it's almost
worthless if you couple the sapphire lightpipe with an optical fiber, since the
fiber is quartz and immediately strips the wide NA off and you lose the view
unless you use some kind of diffuser between them.

Keep in mind, this is all from memory so I could be wrong on several
particulars. But it's what my poor memory tells me.

Jon

 

[Rene Tschaggelar]

Nicholas O. Lindan wrote:

are indeed AR coated...

I'll be darned. It's a coating of TiO2 --

http://www.titaniumart.com/titanium-info.html

I had always thought of titanium oxide as the
'white pigment' in paints, etc.

Fabulous stuff.
This TiO2 can also be baked into glass to make it conductive.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[Ken Smith]

In article <pan.2004.10.19.01.48.15.911797@example.net>,
Rich Grise <rich@example.net> wrote:
[.....]

is acrylic IR transparent?

Yes, acrylic is IR transparent (mostly)
They make lenses for IR work out of the stuff.

--
--
kensmith@rahul.net forging knowledge

 

[Mark Fergerson]

Rich Grise wrote:

On Mon, 18 Oct 2004 19:38:24 +0000, Jonathan Kirwan wrote:


On Mon, 18 Oct 2004 11:12:36 -0700, Mark Fergerson <nunya@biz.ness> wrote:


Anybody got a better set of Google terms that what I
thought were obvious, or maybe a decent website preferably
with some damn numbers?

I don't, right off the bat. But I would anticipate that the sensitivity would
be poorly controlled (in other words, some batches will behave differently than
other batches) in order to keep the whole process as cheap as reasonable and
that the overall response would be otherwise similar to the usual Si based lower
cost detectors you might find in a Hamamatsu catalog. Roughly speaking.

But I'll be interested to hear what you discover here.

Oh, he didn't say anything about doing any discovery - he just posted to
the group to get the answer without doing any of his own homework, like we
all do! ;-)

Now Rich, that's unfair. I said I Googled myself silly.
Apparently I simply lacked some appropriate search terms.

But I'm really, really intrigued by the app here.

Is quartz really IR transparent? I know it's one of very few items
transparent to UV.

How hard would it be to make some fake gems out of acrylic? Do they have
to have realistic heft? And, is acrylic IR transparent? What plastic do
they use for the windows on remotes?

Heft would be nice as would durability, and yes, quartz
is good deep into the IR. I'm leaning toward clear quartz (I
have plenty of old-fashioned radio crystals on hand)
roughened on the back side to act as a diffuser.

Mark L. Fergerson

 

[boB]

On Tue, 19 Oct 2004 02:09:53 GMT, "Clarence" <no@No.com> wrote:

"Nicholas O. Lindan" <see@sig.com> wrote in message
news:GDZcd.857$ta5.723@newsread3.news.atl.earthlink.net...
"Mark Fergerson" <nunya@biz.ness> wrote

See, I plan to hide said scavenged cells under simulated
gemstones (don't ask why), and now I get to
find suitable fake stones that will pass enough NIR to be
worthwhile.

Some minerals should pass IR very well. I know quartz does,
that should open up a whole range of colored quartzs. I have
a suspicion that garnet is also IR transparent. And diamond
certainly is.

There are lenses made of Germanium! They look gray in visible light, but work
as lenses for IR.

Yes, germanium. We (at work) had a $50,000 IR camera for a week and
the salesman told us the lens was made of gerrmanium. expensive
lenses too....

boB

 

[Rich Grise]

On Mon, 18 Oct 2004 19:38:24 +0000, Jonathan Kirwan wrote:

On Mon, 18 Oct 2004 11:12:36 -0700, Mark Fergerson <nunya@biz.ness> wrote:

Anybody got a better set of Google terms that what I
thought were obvious, or maybe a decent website preferably
with some damn numbers?

I don't, right off the bat. But I would anticipate that the sensitivity would
be poorly controlled (in other words, some batches will behave differently than
other batches) in order to keep the whole process as cheap as reasonable and
that the overall response would be otherwise similar to the usual Si based lower
cost detectors you might find in a Hamamatsu catalog. Roughly speaking.

But I'll be interested to hear what you discover here.

Oh, he didn't say anything about doing any discovery - he just posted to

the group to get the answer without doing any of his own homework, like we
all do! ;-)

But I'm really, really intrigued by the app here.

Is quartz really IR transparent? I know it's one of very few items
transparent to UV.

How hard would it be to make some fake gems out of acrylic? Do they have
to have realistic heft? And, is acrylic IR transparent? What plastic do
they use for the windows on remotes?

Thanks,
Rich