Synthesis of colloidal CuInSe2 nanocrystals films for photovoltaic applications

We synthesise 7 nm CuInSe2 nanocrystals of low size and shape dispersion using copper(I) chloride, indium(III) chloride and selenourea as the precursors. The obtained nanocrystals are deposited on indium tin oxide (ITO) covered glass by means of layer-by-layer dip-coating. After each deposition step, a ligand exchange process with 1,2-ethanedithiol (EDT) is carried out. The new ligands interconnect the nanocrystals, which therefore become insoluble during subsequent dip-coating steps. Furthermore, the small EDT molecules replace the long insulating alkyl chains of the oleylamine stabilizing ligands used during the synthesis. I/V measurements of a 1 μm thick film sandwiched between the ITO substrate and an aluminium electrode show a current density of 1 μA/cm2 at 1 V in the dark, which increases to 16 μA/cm2 under illumination with white light.

► We synthesize colloidal chalcopyrite CuInSe2 nanocrystals of 7 nm diameter.
► Layer by layer deposition of nanocrystals' thin films is achieved by treatment with cross-linking surface ligands after each deposition step.
► A photocurrent density of 16 μA/cm2 is obtained under white light illumination.