Well, that's neat.

But where is that really relevant? Typical albedo of anything around a solar panel seems to be like around .2, meaning that these cells which have 23% efficiency on the front, and ~21% on the back.
Solar Irradiance is usually less than 7kWh/m²day.
So this Panel could get around 1.6kWh/m²day on the front and 0.3kwH/m²day on the back.

Isn't cost way more relevant than getting a few more % efficiency?

As long as "we" (as in humanity) can't afford to put solar panels on the top of every/most surfaces that we build, it seems that driving down the cost is more paramount.
Luckily that is happening too though

Wow, that's great for planets in twin star systems.

Hmm, I talked with grid solar people who've been using this for a while about a year ago. Maybe this is a new version? Anyway, they were saying that it really helps in the winter when you can harvest the reflected light from the snow. But doesn't do a ton usually.

TLDR; the front side is 23% efficient, and the rear side 20% efficient.

They don't actually give an overall efficiency but it implies a total of 43%. They compare this to typical panels also at 23% efficient, so it's really remarkable if true. Other emerging solar tech is up to about 32% but if that could also benefit from multiple layers then total efficiency could become insane.

Seems a little too good to be true, really, but great if so.

Edit: Yeah, I don't think these efficiencies can be added like that. I guess the overall efficiency will depend on how reflective the ground under the panels is, and they will extract 20% of that. Maybe that's why they don't give an overall rating.