This review article by Qinrong He and Joe Briscoe explores the advancements and applications of piezoelectric energy harvesters, which convert ambient mechanical vibrations into electrical energy. The authors discuss the structural designs and fabrication techniques of inorganic and organic piezoelectric materials, including piezoelectric ceramics, ZnO nanostructures, PVDF, and its copolymers. They also delve into factors affecting performance and strategies to enhance efficiency, such as chemical doping, surface treatment, and junction effects. The review highlights the progress in flexible energy harvesters for wearable technologies and the potential of various piezoelectric materials in harvesting different forms of mechanical energy. Additionally, it addresses the challenges and future directions in the field, emphasizing the importance of reducing screening effects and improving device flexibility and stretchability.This review article by Qinrong He and Joe Briscoe explores the advancements and applications of piezoelectric energy harvesters, which convert ambient mechanical vibrations into electrical energy. The authors discuss the structural designs and fabrication techniques of inorganic and organic piezoelectric materials, including piezoelectric ceramics, ZnO nanostructures, PVDF, and its copolymers. They also delve into factors affecting performance and strategies to enhance efficiency, such as chemical doping, surface treatment, and junction effects. The review highlights the progress in flexible energy harvesters for wearable technologies and the potential of various piezoelectric materials in harvesting different forms of mechanical energy. Additionally, it addresses the challenges and future directions in the field, emphasizing the importance of reducing screening effects and improving device flexibility and stretchability.