Converters cannot increase power, but they may optimise the power source loading, allowing the maximum output to be realised.A much, much, muuuuccchhhh better analogous word is pressure, since it is possible to have voltage with zero current. Please stop saying speed.
I think I speak for all of us when I say your idea is not entirley clear, if you could please post a schematic or block diagram it would be most helpful.
In any case, you can't increase power through a buck converter, you can only do that through adding a power source.
I wonder if the OP's ideas about "speed" came from an analogy to an automotive gearbox? (NB moderators, an analogy only.)
In this situation, selection of the appropriate gear ratio allows the engine to run at an appropriate speed so that it can deliver full power. You can't get more horsepower than the engine has available, but you can certainly get less available power with the wrong gearing.
I really do not like the voltage = speed analogy either, but it does work to a degree. It goes like this: an engine has a certain torque/speed characteristic, just as the solar panel has a certain current/voltage characteristic. The solar panel maximum voltage is a bit like the maximum rpm limit, and the maximum current is a bit like the maximum torque.
That said, the the analogy breaks down at the extremes as the panel will deliver full current into a short-circuit, whereas an internal combustion engine will stall below a minimum rpm. The panel voltage limit is inherent, with no prospect of connecting rods coming out of the side, so the engine would have to be imagined as having an effective rpm limiter.
It is important in the end to remember that this is just an analogy: electric potential is not really the same as speed. The analogy of voltage with pressure and current with fluid flow is more commonly used, and in my opinion easier for a general audience to understand.