<p>Piezoelectric materials are functional materials that convert mechanical energy into electrical signals and vice versa. This paper reviews the current status of research on piezoelectric materials, involving inorganic ceramics, organic polymers, and hybrid composites, along with their respective advantages and disadvantages in terms of energy conversion efficiency, flexibility, and environmental protection. Specifically, with the development of microstructural engineering, doping strategies, and other advanced fabrication techniques, the performance of various piezoelectric materials such as PZT, KNN, BTO, PVDF, and MXene-reinforced composites has been continually improved. Building on these material developments, practical applications have expanded into diverse fields, including biomedical energy harvesting devices, structural health monitoring systems, portable electronics, and green energy collection etc. Concurrently, machine learning methods have also been developed in the field of materials discovery and device structure design, promoting the data-driven optimization. Despite significant progress, several challenges persist, such as the brittleness of inorganic materials and the relatively low conversion efficiency and environmental instability of organic materials. New research directions have also been put forward, including advanced computational methods, combination of 2D materials, and green device design. Through this comprehensive overview, we aim to provide a clearer understanding of the development direction of piezoelectric materials and advance the construction of powerful, efficient energy-harvesting systems for various applications.</p>