Ternary and quaternary chalcopyrite Cu(In1−xGax)Se2nanocrystals: organoalkali-assisted diethylene glycol solution synthesis and band-gap tuning

Abstract

In this work, four organoalkali-assisted diethylene glycol solution chemical syntheses, using triethylenetetramine, ethanediamine, N,N-dimethylformamide and triethanolamine as assisting agents, CuCl₂·2H₂O, InCl₃·4H₂O, GaCl₃ and Se powder as precursors, N₂H₄·H₂O as the reductant and polyvinylpyrrolidone as the dispersant, were applied to prepare ternary and quaternary chalcopyrite CuIn_1−xGa_xSe₂ nanocrystals (0 ≤ x ≤ 1). The synthesized products were characterized by XRD, TEM, FESEM, EDX, ICP-MS, Raman, and UV-vis-IR measurements. The dynamic concentrations of fed solutions with reaction time were qualitatively described under non-organoalkali-assisted and organoalkali-assisted conditions. The organoalkali-assisted effects were discussed according to the different alkaline intensity and chelating ability to the monomer precursor species. Chemical stoichiometry control and band-gap tuning of the synthesized ternary and quaternary chalcopyrite CuIn_1−xGa_xSe₂ nanocrystals were investigated by simply changing In/Ga atomic ratios of the fed solutions in the diethylene glycol based solution process with the optimized triethylenetetramine-assisted amounts. The results showed that the triethylenetetramine-assisted diethylene glycol solution synthesis was a facile and effective way to control the chemical stoichiometry and band-gap energies for single-phase, well-dispersed, near-granular shaped CuIn_1−xGa_xSe₂ nanocrystals with a size range of 10 nm–20 nm.