This book presents an overview of both the theory and experimental methods required to realize high efficiency solar absorber devices. It begins with a historical description of the study of spectrally selective solar absorber materials and structures based on optical principles and methods developed over the past few decades. The optical properties of metals and dielectric materials are addressed to provide the background necessary to achieve high performance of the solar absorber devices as applied in the solar energy field. In the following sections, different types of materials and structures, together with the relevant experimental methods, are discussed for practical construction and fabrication of the solar absorber devices, aiming to maximally harvest the solar energy while at the same time effectively suppressing the heat-emission loss. The optical principles and methods used to evaluate the performance of solar absorber devices with broad applications in different physical conditions are presented. The book is suitable for graduate students in applied physics, and provides a valuable reference for researchers working actively in the field of solar energy.