This book provides a fundamental discussion, latest research & developments, and the future of thin films and photoenergy materials, two developing areas that have the potential to spearhead the future of industry. Photoenergy materials are expected to be a next generation key material to provide secure, safe, sustainable and affordable energy. Photoenergy devices are known to convert the sunlight into electricity. This type of devices is very much simple in design with having a major advantage with their structure as stand-alone systems to provide outputs up to megawatts. They have been applied as a power source, solar home systems, remote buildings, water pumping, megawatt scale power plants, satellites, communications, and space vehicles. With such a list of enormous applications, the demand for photoenergy devices is growing every year. On the other hand, thin films coating, which can be defined as fusion of surface science, materials science, and applied physics, are progressing as a unified discipline of scientific industry. A thin film can be termed as a very fine or thin layer of material coated on a particular surface, that can be in the range of a nanometer in thickness to several micrometers in size. Thin films are being applied it a number of fields ranging from protection purposes to electronic semiconductor devices.