On the contrary, it would have to be efficient indeed to do anything useful underneath all of the shielding that we'd need to keep those baser forms of radiation at bay. Gamma rays: yuck.

There's nothing to optimize here, neutrinos just interact very very weakly with anything else because they don't carry charge (so no electrical interactions), don't carry color charge (so no nuclear interactions), don't carry weak charge (so no weak force interactions) and have tiny tiny masses, but they are still bosons (so don't act as field carriers like photons do, they're just regular matter). Their low chance of interacting with matter is a fundamental property of them, there's nothing you can do about it through technology, just like you can't create heavier electrons or weaker quarks.

Neutrinos interact extremely weakly with ordinary matter, which is why the detectors are typically huge volumes of water. Even then, the neutrinos interact with the purpose-built detectors on the order of one in a trillion. A neutrino power generator is not a feasible thing to build.

It's an enormous amount of energy packed into a single tiny particle.

But it's still just a single tiny particle, so it's not a lot of total energy.

It's like how you can lift a heavy weight for a second, but that's all you can do. You would need to be able to lift it for hours to be useful as a replacement for a crane. Same idea: Intensity vs total work.

If we had the ability to detect neutrinos in such a small volume as a solar panel they’d be immensely valuable for communication - we’d be able to beam signals directly through the Earth, or through deep water.

It might improve the quality of neutrino astronomy to have the world's solar panels also be neutrino detectors.