This book is an introductory text for graduate students, researchers in industries, and those who are just beginning to work on organic electronics materials, devices and their applications. The book includes mainly fundamental principles and theories for understanding organic electronics materials and devices, but also provides information about state-of-the-art technologies, applications and future prospects. These topics encompass physics for organic transistors, structure control technologies of polymer semiconductors, nanomaterials electronics, organic solar cells, organic electroluminescence and dynamics for excitation, among others. In this second edition, the topics that have had particular progress in the field of organic electronics over the past seven years were added. For example, Thermally Activated Delayed Fluorescence (TADF) technology for organic LED, the development of perovskite materials, light-emitting materials using nanomaterials and the development of skin sensors and wearable/embedded devices. The recent scientific understanding of organic electronics is also introduced. This book will help readers to be able to contribute to society with the technologies and science of organic electronics materials in the future.