As the key approach to enhance the efficient application of solar energy, solar selective absorbers have been extensively investigated in the past years. With great efforts contributed by scientists and engineers all around the world, new materials and excellent structures were achieved in solid progress to stimulate applications in broad fields. In this book, we will present an overview of both theory and experimental methods to fulfill the high-efficiency solar absorber devices. It begins with a historical description of the study and development for the spectrally selective solar absorber materials and structures based on the optical principles and methods in past decades. The optical properties of metals and dielectric materials are addressed to provide the background on how to realize high performance of the solar absorber devices applied in the solar energy field. In the following sections, different types of materials and structures, including the experimental methods, are discussed for practical construction and fabrication of the solar absorber devices, aiming at maximally harvest the solar energy, at the same time to suppress the heat-emission loss effectively. 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 will be suitable for graduate students in applied physics fields with valuables reference also for the researchers working actively in the solar energy fields.