First investigation into the physical characteristics of GO-Doped CuO-ZnO thin films as a secondary absorption layer in CIGS solar cells

In this work, undoped and graphene oxide (Go) doped CuO-ZnO mixed oxide thin films were deposited on glass substrates by spray pyrolysis technique. The effect of doping concentration on the physical properties of the deposited layers, had been investigated. XRD results of graphene doped CuO-ZnO mixed oxide flms show crystallized graphene phase for high doping percentage of 8 %. The morphological characterization revealed a good homogeneity at the surface with good dispersion of graphene nanoparticles over the entire surface. Optical measurements indicated an increase in transmission and in the band gap energy up to 75 % and 2.75 eV, respectively, occurring as the doping rate increased to the values. The new graphene oxide (Go) doped CuO-ZnO mixed oxide thin films were used to improve the efficiency of CIGS solar cell. The new simulated solar cell FTO/ ZnO/CdS/CZO:Go /CIGS/MO,With CZO:Go /CIGS represent the double absorber layer, was studied. An increase in efficiency from 21.5 to 29.68 % was achieved after adding CZO:Go as a second absorber layer which can be explained by the possibility of the second absorber layer to absorb more photons and by band gap engeneering structure of the proposed solar cell.