If your solar system has batteries that store electricity from the sun your solar system will provide power to your home during a blackout or when the sun is not shining.
If your solar system doesn't have batteries then it will provide electricity as long as the sun is shining.
Most solar panels installed in homes will have batteries that store the electricity to be used when the sun is not shining so as long as your solar panel batteries are good then you should have electricity during a blackout even when the sun is not shining.
Having solar panels is a good idea for blackouts so you can have at least some electricity while waiting on the main electric to be restored.