A photon rocket would produce momentum p by consuming energy E=p*c. That's a very poor E/p ratio (since c is large). Meanwhile, old fashioned chemical rockets and ion drives emitting mass m at speed v, supply momentum p=m*v, at energy cost E=m*v^2/2. Here the E/p ratio is v/2. That is far superior to the photon drive. Like 30000 times better. But the photon rocket would have the advantage that no mass would be consumed (if the energy supply was free, e.g. came from solar power). Even that advantage might be small because you could save mass by making v large (e.g. using small particle accelerator as ion rocket) still tremendously outperforming the photon rocket on E/p ratio, while only consuming small mass. And also since your solar panel would provide more "thrust" than your photon rocket that it powered. So... I conclude the photon rocket idea is bullshit.