Understanding the Phase Behavior and Photovoltaic Potential of Solvothermally Synthesized Iron Pyrite

Iron pyrite (FeS2) is a non-toxic, earth-abundant material with exceptional optical and electronic properties, making it a strong candidate for photovoltaic applications. Despite its high absorption coefficient and an indirect band gap of 0.95 eV, its practical use is hindered by low power conversion efficiency (PCE) and reduced open-circuit voltage due to structural defects and impurities. This study explores solvothermal synthesis under varying conditions to optimize phase purity, morphology, and optical characteristics. Structural characterization revealed that phase-pure pyrite was achieved at 180ÅãC with 1 g sulfur, whereas higher temperatures led to impurities like marcasite and pyrrhotite. Optical analysis showed a direct band gap of 2.8 eV and an indirect band gap of 0.95 eV, promoting efficient light absorption. Photovoltaic modeling predicted a theoretical PCE of 25% for pure pyrite films. However, impurities degraded optical performance and carrier transport properties, underscoring the need for impurity control and defect passivation strategies. This work highlights pyrite' potential as a low-cost photovoltaic material and emphasizes further optimization for scalability and performance improvements in sustainable solar energy technologies.