Synthesis of Ternary CuInS₂ Nanocrystals; Phase Determination by Complex Ligand Species

Abstract

Colloidal CuInS 2 nanocrystals were synthesized in a hot organic solvent containing surfactant molecules. The CuInS 2 phase was controlled by the ligand species of the metallic monomers. When the metallic monomers were coordinated with trioctylphosphite, the resulting CuInS 2 had a chalcopyrite or zincblende phase. When the metallic monomers were coordinated with hexadecylamine or oleylamine, the thermodynamically metastable wurtzite phase appeared. The experimental results indicated that the obtained phase was predominantly determined by the growth rate of the nanocrystals. The bond strength between the metallic monomers and ligand molecules and steric size of the ligand molecules influenced the growth rate. The CuInS 2 nanocrystals showed photoluminescence in the near-infrared region. Its energy was far from the optical energy band gap; the luminescence was attributable to the electron-hole recombination via deep defect levels. In the photoluminescence spectrum of the CuInS 2 /ZnS core/shell nanocrystals, a band near the optical energy band gap, whose Stokes' shift was ∼50 meV, appeared. The band was suggested to be attributable to the defect-related emission from CuInS 2 -ZnS alloy formed at the interfaces between the core CuInS 2 and shell ZnS.

Synthesis and formation mechanism of CuInS2 nanocrystals with a tunable phase

“…[26][27][28] An assumption that the phases of CIS nanocrystals were determined by the growth rate of the nanoparticles was put forward. 29 The strong bonds between the metallic monomers and ligand molecules and/or large steric bonds of the ligand molecules decreased the growth rate, which resulted in obtaining the thermodynamically stable chalcopyrite phase CIS; otherwise resulting in obtaining the kinetically stable wurtzite or zinc blende phase CIS. A clear understanding of the observed effects of the reaction conditions on the phase determination, however, is still lacking.…”

Colloidal semiconductor quantum dots; syntheses, properties and applications

“…47) However, the Stokes shifts of reported CuInS 2 QDs are generally large. 36),45),48)50) The exception to this was the PL emission of CuInS 2 /ZnS core/shell QDs with a Stokes shift of ³60 meV, reported by Nose et al 51) This emission was unfortunately very weak, and an intense emission with a large Stokes shift simultaneously appeared. PL emission with a large Stokes shift has been attributed to donoracceptor pair (DAP) recombination in most previous studies.…”

On-line monitoring of solar cell module production by ellipsometry technique

“…III-V multi-Junction tandem cells or high multiple exciton generation nanoparticles with tunable optical gaps) or cheaper thin film technologies such as the Cu 2 ZnSn(S,Se) 4 (CZTS) quaternary semiconductor compound which has similar properties as CdTe and CIGS! [27][28][29][30][31][32][33][34][35][36][37] Fast SE-mapping by expanded beam ellipsometry…”