The second volume, Foundations of Carrier Transport, presents a catalogue of the physics of carrier transport in semiconductors with a view to energy device models. We systematically explain the diffusion-drift model that is central to solar cell operation, the different responses of band bending and electrical field distribution that occur when a voltage is applied to a device with contacts and the central issue of injection and mechanisms of contacts. We describe the carrier transport in disordered materials that often appear as good candidates for easily processed solar cells. There are also excursions into other important topics such as the transistor configuration and the frequency domain techniques as Impedance Spectroscopy that produce central experimental tools for the characterization of the devices.