Smallest solar power source

[SydB]

Hello all. I need to generate a few nanoamps (no more than 100) at >3.5V (so no more than 0.5microwatt) from Sun light. Critically, I need it to occupy no more than about 3 x 3mm (x 1mm thickness); the smaller the better. For the life of me I cannot find any SM photodiodes small enough to array together or that come in a suitably arrayed package. I want to avoid using LEDs if possible as I would rather the increased efficiency I expect photodiodes would give (but I am not sure about that). If I cannot find anything, I will try arraying some LEDs as it appears these are available smaller than any photodiodes.

I need something like this but in a much smaller package:
http://www.clare.com/Products/SolarCell.htm
(why do they put a tiny solar area in such a relatively massive package?)

Does anybody know of any such component on the market or has anybody any suggestions?

 

[(*steve*)]

The current is less of a problem than the voltage. Have you tried a blue SMD LED?

 

[SydB]

Thanks for the quick response, Steve. I am figuring LEDs in series are the best answer, too. I shall have to experiment with frequency bands of the different coloured LEDs (are you thinking blue because the bandgap potential is higher for blue and white?). Red seem to be ok in sunlight, though, and available in the very smallest packages, and cheap. Quoted 'brightness' and viewing angle are other factors I will need to experiement with.

 

[Martaine2005]

What about a quick shop at poundland! Better still, the 99p shop.
They usually have tiny solar lights running off 2AA batteries (3V).
Might be worth looking into?

EDIT: Sorry, didn't read properly. Ignore my post..

Martin

 

[frhrwa]

Hello all. I need to generate a few nanoamps (no more than 100) at >3.5V (so no more than 0.5microwatt) from Sun light. Critically, I need it to occupy no more than about 3 x 3mm (x 1mm thickness); the smaller the better. For the life of me I cannot find any SM photodiodes small enough to array together or that come in a suitably arrayed package. I want to avoid using LEDs if possible as I would rather the increased efficiency I expect photodiodes would give (but I am not sure about that). If I cannot find anything, I will try arraying some LEDs as it appears these are available smaller than any photodiodes.

I need something like this but in a much smaller package:
http://www.clare.com/Products/SolarCell.htm
(why do they put a tiny solar area in such a relatively massive package?)

Does anybody know of any such component on the market or has anybody any suggestions?

What about the one in a watch?

 

[SydB]

Can you be more specific? Solar powered watches that I have seen use a significant part of the face surface area. Have you seen one where the solar sensitive area is less than 3 x 3mm?

 

[Alec_t]

How about a bunch of these?

 

[SydB]

How about a bunch of these?

Thanks for that but I am not sure a phototransistor can act as a power source. Do you know if it can?

 

[Alec_t]

Don't see why it couldn't be operated in photo-voltaic mode, but I've no idea how much current you could draw.

 

[SydB]

I shall try some. They are infra red but I shall see what happens. Thanks.

 

[Alec_t]

Solar power would have a fair infra-red content, but if that is a concern then I'm sure there are similar-size visible-light phototransistors readily available.

 

[SydB]

Actually, I believe solar has relatively little power in infra-red compared to, for example, green. But it will all be down to the surface area available on the silicon so it's probably just a case of testing.