This is possible to some extent.
However, solar panels are still quite inefficient. Even with top panels, about 80% of the power heats the panel instead of coming out in electrical form.
Semiconductors stop being semiconductors above some temperature. That's about 150 °C for silicon. You can't let the panel get that hot, since it won't produce any electric power anymore.
Even below the max semiconductor temperature, solar panels become less efficient. The current is roughly proportional to the light flux, but the voltage goes down with temperature. Since output power is current times voltage, a hot solar panel is less efficient than a cool one, all else being equal.
Consider that full-on sunlight has a power of about 1.2 kW per square meter at optimum conditions at the surface of the earth. Even using a more realistic value of 1 kW/m2, that's still 800 W/m2 to get rid of to keep the panel operational. That's about 520 mW per square inch, which may be helpful if you're used to heat sinking transistors and the like.
So some amount of extra flux works, but you can't take it too far. The efficiency will go down, but the total power output is still more than a bare panel. However, if you overdo it, the panel gets too hot and you get no power at all, plus possible permanent damage to the panel.
In terms of absolute power collection, it's always better to add more panel area than to spend that area concentrating light onto a smaller panel. In some cases, economics favors some concentration of light (mirrors are cheaper than solar panels).