Room temperature non-vacuum preparation of nanocrystalline CuInSe2 employing aqueous solvents

A new room-temperature, aqueous solution-based preparation method for chalcopyrite CuInSe
₂
has been developed. Using 10% aqueous ethylenediamine as a solvent, the slow addition of Cu(NO
₃
)
₂
to a mixture of indium(III) acetate, elemental Se, and sodium thioglycolate results in the formation of CuInSe
₂
as characterized by Raman spectroscopy. During this reaction, a kinetically-stable Cu
_2-x
Se(s) intermediate initially forms followed by slow conversion to CuInSe
₂
that likely involves a direct Cu
_2-x
Se + In
₂
Se
₃
solid-state reaction. The ethylenediamine in the reaction mixture acts as a complexing agent, establishing equilibria that can be in competition with Cu
_2-x
Se(s) formation, limiting particle size and accelerating rates of reaction with In. Over several hours, the CuInSe
₂
material undergoes a phase decomposition that can be reversed by annealing at 550 °C. Attempts to prepare CuIn
_1-x
Ga
_x
Se
₂
and CuGaSe
₂
via this method result primarily in CuInSe
₂
and Cu
_2-x
Se products, respectively, with nearly all gallium staying in the solution phase.