This book is expected to present state-of-the-art understanding of a selection of excitonic and photonic processes in useful materials from semiconductors to insulators to metal/insulator nanocomposites, both inorganic and organic. Among the featured applications are components of solar cells, detectors, light-emitting devices, scintillators and materials with novel optical properties. Excitonic properties are particularly important in organic photovoltaics and light emitting devices, as also in questions of the ultimate resolution and efficiency of new-generation scintillators for medical diagnostics, border security and nuclear non proliferation. Novel photonic and optoelectronic applications benefit from new material combinations and structures to be discussed.