Development of low-cost PV devices by using nanocrystal ink of light-absorbing CIGS semiconductor layer

Copper indium gallium diselenide Cu(In1-xGax)Se2 (CIGS) nanocrystals were successfully synthesized by "heating-up" process. Monodisperse nanocrystals with an average diameter of 13.6 nm and a size deviation of 3.4 nm were obtained. CIGS showed a chalcopyrite single phase with the desired stoichiometric composition. In this work, we report high quality semiconductor nanocrystal films obtained by non-vacuum, facile and cheap procedure of synthesis and deposition. Thin films of CIGS (~ 100 nm in thickness) were obtained by nanocrystal dispersion in non-polar organic solvent and by spry-deposition of the resulting ink onto ITO conductive glass substrate without any post annealing treatment. Nanocrystals and their thin films were characterized by several techniques, such as TEM (transmission electron microscopy), EDX (energydispersive X-ray spectroscopy), XRD (X-ray diffraction), UV-vis-NIR absorption spectroscopy and photocurrent measurements. CIGS behave as light-absorbing layer in thin-film PV devices, the in solution-processability presented in this work and the possibility of large-scale synthesis enable the fabrication of thin films on lightweight and flexible plastic substrates, opening promising perspectives for producing cheaper and more efficient nanocrystal PV devices.