Evolution of nanoplate morphology, structure and chemistry during synthesis of pyrite by a hot injection method

Pyrite (FeS₂) has a high light absorption coefficient and a suitable bandgap for photovoltaic applications but its poor performance in experimental cells has precluded its use until now. This is attributed to impurity phases and defects. It is important to understand the actual reasons to overcome these fundamental problems. Here we investigate the synthesis of pyrite nanoparticles by a hot injection method to understand the effects of synthesis parameters on the initial monomer concentration, nanoparticle size, morphology and the structure. Nanoparticle shapes such as cubes, plates and spheres were obtained and a mechanism for their formation is proposed. Experimental evidence is obtained to substantiate the model. Detailed study of the nanoplate evolution shows that it involves a nucleation stage followed by a self-assembly process to form the plate framework. The nanoparticles also appear to nucleate as FeS first and then transform to FeS₂.