It's the foundational principle of "Launch Windows." Because the earth rotates the sun and also spins on an axis, we can launch at a time of day that gives us time to accelerate and then leave earth orbit in the direction of earth's orbit around the sun with minimum amount of energy required. The majority of energy used is simply to escape Earth orbit. Once orbiting the sun, comparatively very little energy would be required to approach it utilizing it's own gravity.

During Perihelion the sun is 147100632 KM away, as the distance from the sun is not constant for earth's orbit.

Still this approach seems wasteful. Just making it sufficiently far from the surface travelling in the right direction should be enough... As long as you aren't in a rush.