Plant the seeds in soil, either outside or in a planting pot.
Water the seeds regularly and make sure the soil is actively exposed to sunlight.
Watch as the plant grows. Plants have extremely complex photo-systems that respond to sunlight by becoming "excited." When sunlight strikes these systems, electrons are transferred to various organic cycles, causing the regeneration of a molecule that provides metabolic energy for the plant. While you will not be able to see these processes happening, you can be sure that the plant grows larger each day because it has an adequate supply of water and sunlight.
Examine your photosynthesis references. You will see that there are not many other biological pathways to convert light energy into chemical energy other than through photosynthesis. Solar cells are devices that are capable of converting light energy into electricity, but this is much different than the photosynthetic process.