4V (50uA) Output Solar Cell in 8-Pin Surface Mount SOIC.

Clock Loop

50uA is short circuit current.

http://www.eeweb.com/company-news/ixys/4v-output-solar-cell

$1.40ea
http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=CPC1822

Mike Green

That's pretty good. A DS1307 RTC takes only 0.5uA in standby mode with the clock running. The TI MSP430 series microcontrollers also have a 0.5uA standby current and, with a low leakage capacitor and maybe 10:1 standby to active time, could do datalogging or something similar with the output of this solar cell. See this TI White Paper.

Ale

Pretty impressive, but It looks like as it could have a bigger exposed surface, like 4 times bigger... or not?

Tracy Allen

They say 50µA short circuit current at 4V in direct sunlight (6000 lux). But 6000 lux is hardly 1/10 of direct sunlight, which is more like 100_000 lux (9290 footcandles). More like an overcast day. Would that imply that the device would generate even more at higher light levels, or is that a typo?

They also say the device is "a monolithic photovoltaic string of solar cells with switching circuitry". Switching circuitry? Does it do something to prevent reverse leakage when the sun is not out?

I don't know the active area, but suppose each element in the stack is 1 mm^2. Full solar input is about 1mW/mm^2, so if the cell is able to convert all of that to current at 0.5V, the current would be 2mA, but lets generously give it 10% efficiency, so 200µA. Okay, it's in the right ballpark for full sun.

Thanks for the link, I want to try one!

Clock Loop

Include a supercap.... (unless the supercap overhead is too much,,,,leakage, efficiency, etc)

I think where this device REALLY shines (pun?) is how its package is not only smt, small, but also pretty durable, solar cells are usually pretty delicate... and not nearly that small.
By the looks of this, its probably one of the most durable solar cells to date.

So this would be a GREAT way to provide wireless power to any device in the sun, or under a street lamp (or outdoor light thats always on) etc...


Or even remote monitoring stations... an array of these smt cells would juice up a cap, and a battery ....
And do it all in a very very small space.

I personally like this device because of its size, and durable package...
It completely works with smt machines and re-flow processes...
Cell phones need these.

Tracy Allen

Tacked one of these onto a Digikey order. It came packaged in a sealed bag with desiccant. The active area appears to be about 1.8mm by 2.5mm.

Ran a quick test on it this afternoon. Here is a graph of the results. This was in full sun, measured with LI-COR pyranometer at 973W/m² and photometer at 102 klux.

Tracy Allen

Checked the reverse current vs voltage in the dark, at room temperature. around -50nA at -3.2V, up to -1µA at -4V. That would slowly drain a battery that had been charged in the light. No overhead room to put in a diode, maybe an fet though. I was intrigued by the data sheet description, "The CPC1822 is a monolithic photovoltaic string of solar cells with switching circuitry"--What might they mean by switching circuitry? No further explanation. It appears to be a straightforward photodiode array, plain and simple.

Lawson

I've found crystalline silicon solar cells often put out 1/2 or less voltage under florescent or LED light. The lack of significant IR appears to be the culprit as the same cells work fine under an incandescent lamp. If this chip array still puts out 4v indoors, that could be what the "switching circuits" do.

Personally I prefer using the Sanyo amorphous solar cells Digikey stocks. They still give good voltage under high efficiency lighting, and can be surface mounted after removing the leads with a temperature controlled iron. Sticking with small crystalline solar cells, a string of BPW34 photo-diodes works well. (up to 0.55V and >1.5mA each in sunlight) Digikey also carries the pre-packaged solar cells that Ixys makes. (again, works great outdoors)

Lawson

Clock Loop

Tracy Allen wrote: »

Checked the reverse current vs voltage in the dark, at room temperature. around -50nA at -3.2V, up to -1µA at -4V. That would slowly drain a battery that had been charged in the light.

Hmm, put two in series? (but you only got 1) Then use diode with desired drop to make v range proper.

Or perhaps a super cap middleman approach...

Tracy Allen

Hi Lawson, I was remembering about your micropower experiments, and jewelry. This chip is definitely a niche thing, and not the most space-efficient that it could be. I see ixys has a lot of solar products available from Digikey, not just this one.

Tubular

Tracy Allen wrote: »

Checked the reverse current vs voltage in the dark, at room temperature. around -50nA at -3.2V, up to -1µA at -4V. That would slowly drain a battery that had been charged in the light. No overhead room to put in a diode, maybe an fet though. I was intrigued by the data sheet description, "The CPC1822 is a monolithic photovoltaic string of solar cells with switching circuitry"--What might they mean by switching circuitry? No further explanation. It appears to be a straightforward photodiode array, plain and simple.

fwiw Clare (now Ixys?) also make these in 8v versions (at half the current), and an SOIC-16 version with 2x the area. The 8v it easier to charge stuff.

here's the full range