Nucleation And Growth Mechanism Of Wurtzite Copper Indium Disulfide Nanoparticles During Solution Processing

Synthesis of Cu-In-S (CIS) nanoparticles by hot injection method using a mixed solution of Cu(acac), In(acac) and DDT in solvents OAm and trioctylphosphine oxide (TOPO), was carried in nitrogen atmosphere. Phase and crystallographic structure evolution were evaluated by extracting samples at intermediate synthesis stages and was characterized by X-ray diffraction and transmission electron microscopy. Ex-situ observation of phases indicated the formation and growth of Cu2S at the earlier stages. With further increase in temperature, CIS formed with the diffusion of In3+ ion. Wurtzite CIS nanoparticles preferentially grew along a length (from -42 to 62 nm) while the width nearly remained constant to about -32 nm. The preferential growth took place along [0002] while the particle width was oriented along [1010], which resulted in nearly oval-shaped nanoparticles. FTIR spectra recorded at different stages of synthesis (50-310 degrees C) pointed towards the ligand exchange mechanism after the addition of sulfur source at (160 degrees C).