Light Absorption Characteristics of Multi-morphology FeS₂ Granular Synthesized Under Hydrothermal Conditions

This chapter examines granular FeS₂ synthesized under hydrothermal conditions of 220 °C, with a Fe/S ratio of 1:3. SEM and XRD characterize its morphology, composition, and structure. Measurement of the absorption spectrum within the range of 200–2,000 nm was performed using Cary 500 UV–Vis–NIR spectrophotometer. The band gap was calculated according to the band gap (eV) formula. The results showed that the samples were granular pyrite in the form of cube and octahedron, with a particle size of about 2–5 μm, and include a certain amount of pyrrhotite (Fe_1−xS). The absorption peak was about 1,879 nm, with the intrinsic absorption edge (λ ₀) and band gap values of 1,885 nm and 0.6578 eV, respectively. Through the relationship between semiconductor conversion efficiency and band gap, we obtained a limiting conversion efficiency which can achieve to about 15 %. We present a brief analysis of the vacancy affection to the band gap of pyrite.