This chapter discusses key concepts and applications in radiation metrics, photometry, and semiconductor physics, with a focus on their impact on photoelectric detection technologies. The challenges faced by China’s semiconductor industry, such as equipment shortages, low yields, and underdeveloped domestic technology, are addressed, with recommendations for strategic investments and international cooperation. The chapter also analyzes mechanisms like the photovoltaic and photothermoelectric effects, and key performance parameters such as sensitivity, response time, and noise equivalent power. It concludes by highlighting research trends in photoelectric materials, pointing toward future developments in high-sensitivity, fast-response, and reliable optoelectronic devices.