Aphids can make their own carotenoids and may be able to capture chemical energy directly from the sun. Green or orange individuals contain more carotenoids and more ATP than white ones. The secret of plant growth is that they capture photons and use them to create high-energy atomic bonds that can be used elsewhere to run chemical reactions that build plant material.
Unlike other organisms, they are not ingesting or otherwise harbouring photosynthetic symbionts such as bacteria or algae. They are making their own photosynthetic chemicals. They may not be able to do full photosynthesis as plants do, but among animals they are unique.
It will be interesting to find out how they evolved this unique (for animals) biochemical machinery.