High efficiency CIGSe solar cells by combinatorially sputtered Cu(In,Ga) followed by selenization

Cu(In_1-x,Ga_x)Se₂ (CIGSe) based solar cells were fabricated using a sulfur-free sequential process. Combinatorial sputtering of Cu, In, and Ga results in a broad range in Cu/(In+Ga), Ga/(In+Ga), and thickness within one sample, allowing an accelerated learning curve to form high quality CIGSe by selenization. A high Ga content at the CIGSe surface allows for high efficiency and V_oc. The structural and optoelectronic properties of the absorber were characterized by SIMS, XRF, SEM, XRD and PL. EQE results confirmed a high band gap (~1.12eV) of the absorber surface. V_oc of 692mV was achieved with best cell efficiency of 17.7%.