Ternary and quaternary chalcopyrite Cu(In1−xGax)Se2 nanocrystals: 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 CuIn1−xGaxSe2 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 CuIn1−xGaxSe2 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 CuIn1−xGaxSe2 nanocrystals with a size range of 10 nm–20 nm.