Got a tip from Lennart Herlaar a long time ago about a tiny CPC1824 solar cell from Clare with 4V output:
It’s packaged as a SOIC-16 chip, so clearly the light collecting capabilities of this thing will be limited. But with all this ultra-low power stuff going on here at JeeLabs, I thought I’d give it a whirl anyway. It’s trivial to hook up:
In bright sunlight, you get over 4V with a 100 µA short-circuit current according to the datasheet.
I added a BAT34 Schottky diode in series (which has a low voltage drop) and placed it all on a little breadboard together with a 0.47 F supercap – the solar chip is mounted on a little SOIC breakout board:
The initial voltage was under half a volt, but rising (very) slowly and steadily while exposed to light.
Let’s just leave this thing exposed to light near a south-facing window for a week or so, eh?