IMPROVED CU(IN,GA)(S,SE)(2) THIN-FILM SOLAR-CELLS BY SURFACE SULFURIZATION

Surface sulfurization was developed as a technique for fabricating eff icient ZnO : Al/ CdS/graded Cu(In,Ga)(S,Se)(2)/Mo/glass solar cells. P rior to the sulfurization, single-graded Cu(In,Ga)Se-2 (CIGS) films we re deposited by a multi-stage process. The sulfurization of CIGS films was carried out using a H2S-Ar mixture at elevated temperatures. The crystallographic and compositional properties of the absorber layers w ere investigated by XRD, SEM and AES analyses. After sulfurization, su lfur atoms were substituted for selenium atoms at the surface layer of CIGS films to form a Cu(In,Ga)(S,Se)(2) absorber layer. The diffusion of sulfur depends strongly on the grain structure of CIGS film. The c ell efficiency of the 8-11% range before sulfurization was improved dr amatically to 14.3% with V-oc = 528 mV, J(sc) = 39.9 mA/cm(2) and FF = 0.68 after the sulfurization process.