This book describes the application of the organic semiconducting polymer polybithiophene (PBT) in two different energy generating devices, solar cells and thermogenerators. In addition, we aimed to electrochemically codeposited reduced graphene oxide (RGO) and analyze it as a component of the active layer composite of photovoltaic devices. The reader will be directed to understand the main theoretical concepts about semiconductor polymers, as well as the operation of photovoltaic and thermoelectric devices. Results obtained from the fabrication and characterization of these devices are also presented, solidifying the concepts discussed in the introductory chapters.