Air-stable CuInSe2 nanoparticles formed through partial cation exchange in methanol at room temperature

Spherical CuInSe2 nanoparticles were synthesized through a partial cation exchange reaction of Cu2-xSe nanoparticles in methanol at room temperature. An additive, tributylphosphine, rapidly reduced copper and selenium ions, and facilitated the dissolution of Cu ions. Poly.vinylpyrrolidone) retained the spherical morphology of the nanoparticles by anchoring on the surface. The fraction of In3+ ions increased as the reaction progressed, which led to a decrease of the optical bandgap from 2.06 eV of Cu2-xSe to 1.03 eV of CuInSe2. The resulting CuInSe2 particles exhibited high air and thermal stability, and can be applied as colloidal inks for thin film fabrication in optoelectronic devices.