Astronomers Propose New Technosignature: Silicon-Based Solar Panels

I doubt this would be a long lived techno-signature. Most advanced civilizations will probably transition to a singularity in 100-200 years (a blip on astronomical time scales).

Exotic energy production methods or harvesting will probably ensue which we would be hard pressed to recognize. Not to say we shouldn’t look for anomalous planetary properties, the energy spectrum is probably still the best bet, though odd chemical compositions is probably a close second.