The global pursuit of clean and sustainable energy has placed photovoltaic (PV) devices at the forefront of renewable energy technologies. This chapter presents a comprehensive overview of photovoltaic (PV) devices, tracing their evolution from early solar technologies to their current and expanding role in the global energy landscape. Beginning with the fundamental principles of the photovoltaic effect and the semiconductor physics underpinning solar cell operation, the chapter explores essential design considerations and device architectures including single and multijunction cells and planar versus textured surfaces. The chapter also explores the details of the materials used in PV technologies, covering traditional crystalline silicon, widely used thin-film compounds like CZTS, CdTe, and CIGS, and promising next-generation materials such as perovskites, organic photovoltaics, and quantum dots. The chapter also reviews key fabrication techniques, from conventional wafer processing to advanced thin-film deposition and emerging printing technologies, with a focus on enhancing performance, scalability, and durability. Applications are discussed across various sectors, including grid-connected systems, building integrated photovoltaics (BIPV), portable electronics, and specialized uses in aerospace and remote environments. Finally, the chapter addresses the technological, environmental, and economic challenges that PV technologies face, while highlighting future trends such as tandem solar cells, AI-driven design optimization, and the integration of PV into smart infrastructure. This synthesis provides readers with a solid foundation in the design, materials, fabrication, and real-world applications of photovoltaic devices, as well as insights into their evolving role in a sustainable energy future.