Glad you enjoyed the post! Interestingly, despite the low efficiency the calculator amorphous panel was by far the most efficient choice for tritium cells that I tried, even beating out the similarly-sized garden light panel, which in sunlight would be more efficient. The calculators are built to charge in low-light (indoors) environment, so they end up working quite well for this application.

It's a shame that link doesn't give out the activity of the tritium content, but I suppose they don't want people to know that it's radioactive (the word tritium isn't even mentioned on the page, even though that's definitely what they are using!). Either way, I'm sure it would produce a much better cell.