Synthesis and characterization of CIS nanoparticle ink for low-cost thin film solar cells.

CuSe and CuInSe2 nanoparticles were synthesized through the aqueous solution process using NaBH4 solution as a solvent and subsequent heat-treatment. Not only the synthesized nanoparticles, CuSe and CuInSe2, but also spray-coated thin films prepared by using CuSe and CuInSe2 were characterized by XRD, SEM-EDS, TGA and UV-Vis spectroscopy. CuSe nanoparticles with a plate-like shape, which were confirmed by XRD and SEM, were directly prepared by a reaction of a mixture of CuCl2 and Se in the aqueous solution of NaBH4 at room temperature. Cu-In-Se compounds were obtained through the reaction of CuCl2, InCl3, and Se in the aqueous solution of NaBH4, were consisted of the mixture of CuSe(x) and In hydroxides, and were transformed into CuInSe2 with a chalcopyrite structure by a heat-treatment at 300 degrees C.

Effects of solvents on the synthesis of CuInSe2 nanoparticles for thin film solar cells.

Chalcopyrite CuInSe2 (CIS) nanoparticles were synthesized in oleic acid, 1-octadecene, oleyl amine and tetraethylene glycol at temperature above 200 degrees C. Depending on the solvent used and reaction temperature, the obtained nanoparticles had different shapes, sizes, chemical compositions, and crystal and thermal properties. CIS powders synthesized in oleic acid, 1-octadecene and oleyl amine above 200 degrees C exhibited chalcopyrite structure. On the other hand, powders prepared in tetraethylene glycol contained a mixture of CIS and CuSe compounds. The CIS powder obtained in oleyl amine had a high thermal stability over 500 degrees C. CIS thin films prepared from nanoparticles were heat-treated in order to observe changes in their property. After 10 min heat-treatment at 500 degrees C, their crystal structure and chemical composition were slightly changed, and their band gap energies were ca. 1.01 eV except in the case of powders prepared in tetraethylene glycol.