Flexible Perovskite Solar Cells: Low Temperature Processing, Material Design, and Pathways to Scalable Green Photovoltaics

Flexible perovskite solar cells (FPSCs) have emerged as a promising next- generation photovoltaic technology due to their lightweight, conformal design, and compatibility with low-cost, scalable fabrication. This review systematically summarizes recent advances in FPSC development, focusing on low-temperature fabrication strategies, functional material engineering, and device integration. We first detail one- step and two-step deposition methods, along with other novel approaches for producing high-quality perovskite films on flexible substrates at reduced thermal budgets. Subsequently, we examine the design of key functional layers, including perovskite absorbers, electron and hole transport layers, flexible electrodes, and substrates, highlighting innovations that enhance performance and mechanical resilience. A dedicated section explores Sn-based perovskite solar cells as a low-toxicity alternative to lead-based systems, covering compositional optimization, device architecture, and their growing deployment in flexible configurations. This review further discusses the scalable realization of flexible perovskite solar modules, including module architecture, charge transport management, and environmental safety strategies such as lead encapsulation and sustainable substrates. We conclude with an overview of application scenarios ranging from wearable electronics and high-altitude platforms to self-powered IoT systems and evaluate commercialization prospects through integrated portable energy systems. Together, these insights provide a comprehensive roadmap toward the development of high-efficiency, mechanically robust, and environmentally responsible FPSCs for real-world deployment.