The text initially surveys the requirements of humanity, the subsequent need for solar cells, the nature of sunlight and the properties of semiconductors. Concrete examples, extensive references and theoretical arguments are then used to present a comparison of options available in the design and operation of solar cells and solar cell systems. The cells - constructed from single, crystal, polycrystalline and amorphous semiconductors - and the systems - have varying designs and differing levels of solar energy for input and produce electricity or electrical and thermal energies. Solar cell production, economics and environmental effects are considered throughout the publication.