This chapter reviews the recent emergence and evolution of sustainable materials designed to convert existing energy sources—like solar, thermal, mechanical, and electromagnetic—into functional electrical power. Particular attention is paid to eco-friendly, biodegradable, and affordable materials, like organic semiconductors, perovskites, piezoelectric polymers, carbon-based nanostructures, bioinspired systems, which not only ensure energy conversion efficiency additionally align with environmental goals due to their reduced ecological footprint and potential for recyclability. This chapter reviews at the underlying mechanisms of energy harvesting in these materials and highlights recent advancements in material synthesis, structural design, and device integration. Important issues are investigated critically, including compatibility with current technologies, scalability, and long-term stability. To maximize material performance and sustainability, the chapter also explores interdisciplinary trends that combine materials science with artificial intelligence, additive manufacturing, and green chemistry. The chapter expects future developments, such as the emergence of multipurpose hybrid materials, the creation of self-powered and self-healing systems, and the incorporation of energy harvesters into implantable and wearable electronics. These developments represent a paradigm shift away from traditional, resource-intensive systems and toward decentralized, intelligent, and sustainable energy solutions. This chapter attempts to give researchers, engineers, and legislators a thorough understanding of the situation and a glimpse into the future of technology to fully utilize sustainable materials in the pursuit of persistent and clean power systems.