Carbon- and Oxygen-Free Cu(InGa)(SSe)2 Solar Cell with a 4.63% Conversion Efficiency by Electrostatic Spray Deposition

We have demonstrated the first example of carbon- and oxygen-free Cu­(In,Ga)­(SSe)2 (CIGSSe) absorber layers prepared by electrospraying a CuInGa (CIG) precursor followed by annealing, sulfurization, and selenization at elevated temperature. X-ray diffraction and scanning electron microscopy showed that the amorphous as-deposited (CIG) precursor film was converted into polycrystalline CIGSSe with a flat-grained morphology after post-treatment. The optimal post-treatment temperature was 300 °C for annealing and 500 °C for both sulfurization and selenization, with a ramp rate of 5 °C/min. The carbon impurities in the precursor film were removed by air annealing, and oxide that was formed during annealing was removed by sulfurization. The fabricated CIGSSe solar cell showed a conversion efficiency of 4.63% for a 0.44 cm2 area, with V oc = 0.4 V, J sc = 21 mA/cm2, and FF = 0.53.