But sunlight is wide spectrum, and a lot of the reasons why the efficiency of regular solar panels is low, is that they don’t absorb all of the spectrum equally well. That’s why there’s all this talk of tandem solar cells with perovskites these days. The two solar cells can be tuned to extract energy from different wavelengths of light.

Since the light they’re making is nearly monochromatic, it’s a lot easier to get higher efficiency. That’s kind of the whole point of the invention.

That's not really relevant. They have a light source that runs on a fuel and are putting multiple PV cells around it. The efficiency they care about is the fuel in to electricity out. If you can put more cells around the light, the system efficiency goes up.

That can't be true. The current record for non-concentrating cells is 39.5% efficiency using triple junction cells [1]

Concentrating cells are at 47.6% [2]

[1] https://www.cell.com/joule/fulltext/S2542-4351(22)00191-X

[2] https://publica-rest.fraunhofer.de/server/api/core/bitstream...