Abstract
FeS2 (pyrite) has been considered as a superior semiconducting material for thin film solar cells since it possesses an appropriate band gap of ~0.95 eV and a very high absorption coefficient (α = 5x105 cm-1). These characteristics coupled with the low cost, environmental compatibility, and abundant elements in the crust make pyrite to be a potential candidate for solar cell material in the form of ultrathin films. Theoretically, a thickness less than 2,000 Ǻ is enough. Pure pyrite nanoparticles (NPs) with sizes from ~10 to 20 nm were synthesized by the solution method. As the surface energy of NPs is significantly higher than that of larger particles, NPs will tend to agglomerate to a size over 100 nm, which disables the formation of smooth, continuous ultrathin films. In this study, a beads-milling technique was applied to disperse the agglomerate and yield well-dispersed pyrite NP inks with an average particle size distribution around 10 to 30 nm. This well-dispersed NP ink was used to acquire smooth and continuous pyrite thin films by spin coating. In order to get well-dispersed pyrite NPs inks by beads milling, experimental parameters such as dispersant type, surfactant type, rotation speeds of rotor blade and weight ratio (WR) of pyrite/ surfactant were tried in this study. A smooth and continuous thin film with thickness of around 30 nm were produced by spin coating with the optimal experimental parameters : 1 wt.% pyrite slurry, a WR (pyrite/Oleylamine) of 10, 1500 rpm of rotor blade rotation speed and 30 min milling time.