Book excerpt: The book describes emerging strategies to circumvent transmission and thermalization losses in solar cells, and thereby redefine the limits of solar power conversion efficiency. These strategies include the use of organic molecules and rare-earth metal materials. Approaches to augment the efficiency of these processes via near-field enhancement are described as well. This book includes a discussion of state-of-the-art implementations of these emerging strategies in solar cells, both internally, as in molecular intermediate band and charge carrier multiplication, and externally, such as photon up- and down-conversion. Tools for characterization are also provided. Written by leading researchers in the field, this book can be useful to both beginners and experienced researchers in solar energy.