CuInSe2, CuGaSe2 and Cu(In, Ga)Se2 nanocrystals synthesized by ambient pressure diethylene glycol based solution process

Single-phase chalcopyrite CuInSe2, CuGaSe2 and Cu(In1 − xGax)Se2 nanocrystals were synthesized by an ambient pressure diethylene glycol based solution process using copper, indium, gallium inorganic salts and Se powder as precursors at temperature 210 °C. Influence of precursor atomic ratios in reaction solutions on crystallization, morphologies, stoichiometry control and optical properties of the synthesized nanocrystals was investigated by XRD, TEM, EDS and UV–vis-IR measurement. The results showed that growing morphology of the synthesized nanocrystals had near-granular polyhedral shape. The crystallite size calculated by Scherrer equation was in the range from 19.8 nm to 14.9 nm. Chemical stoichiometry of the synthesized nanocrystals could be tuned by changing precursor atom ratios in the reaction solution and the corresponding band gap energies were changed in the range of 1.03 eV–1.72 eV.

Graphical abstractThe picture shows the variation of (αhν)2 versus (hν) for the four CIS-based nanocrystals in ethanol solution, displaying optical band gap energy of 1.03 eV, 1.20 eV, 1.40 eV and 1.72 eV, respectively for CuInSe2, Cu(In0.75Ga0.25)Se2, Cu(In0.5Ga0.5)Se2 and CuGaSe2 nanocrystals, demonstrating the effective tuning of band gap energy with different In/Ga atom ratios.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Common DEG route solution synthesized ternary and quaternary CIS-based nanocrystals. ► Chemical stoichiometry control was probed by changing reaction solution constitutes. ► Band gap energy of nanocrystals was effectively tuned by different In/Ga atom ratios.