This book provides an advanced-level exploration of lead-free perovskite materials, covering their synthesis, structural and electronic properties, and diverse applications. As the global scientific community seeks high-performance materials with reduced environmental impact, lead-free perovskites offer groundbreaking potential for enhancing device efficiency while ensuring sustainability. With the rapid advancements in nanoscience and nanotechnology, lead-free perovskite materials have emerged as a promising alternative to conventional lead-based perovskites, addressing critical environmental and toxicity concerns. These sustainable materials exhibit remarkable properties, making them highly attractive for applications in photovoltaics, optoelectronics, gas sensors, catalysis, energy storage, and beyond. Key topics include:Synthesis and characterization of lead-free perovskites using solution processing, vapor deposition, and emerging fabrication techniques. Photovoltaic and optoelectronic applications, including solar cells, LEDs, photodetectors, and lasers. Advanced functionalities, such as gas sensing, catalysis, energy storage, thin-film transistors, and piezoelectric devices. Novel applications in emerging technologies, including memristors, thermoelectrics, magnetic materials, and imaging devices. Future challenges and opportunities, addressing stability, scalability, and commercial viability. Bringing together contributions from leading researchers, this book offers a comprehensive review of recent advancements and emerging trends in lead-free perovskite materials. It serves as an essential reference for materials scientists, physicists, chemists, and engineers working in sustainable energy and nanotechnology.