The driving force of photosynthesis is SUNLIGHT ENERGY.
Green plants have the capacity to manufacture their own foods, through the process of photosynthesis, as the result of chlorophyll which their cells contain. The chlorophyll has the ability to trap the energy from the sun and use it to drive the process of photosynthesis. The major function of sunlight in photosynthesis is to break down the water molecules and turn them into high energy electrons that are capable of forming ATP molecules.