Lateral inhomogeneity of the Mg/(Zn+Mg) composition at the (Zn,Mg)O/CuIn(S,Se)2 thin-film solar cell interface revealed by photoemission electron microscopy

Spatial variations in the chemical composition of the (Zn,Mg)O/CuIn(S,Se)2 thin-film solar cell interface were studied by photoemission electron microscopy (PEEM). Energy filtered PEEM images indicate significant differences in the magnesium and zinc distribution. Local photoemission measurements reveal a relative difference in the derived Mg/(Zn+Mg) composition of the (Zn,Mg)O material of up to (11.4 ± 0.7)%, which can be expected to induce band gap fluctuations of (60 ± 30) meV. Furthermore, local areas with significant accumulations of sodium could be observed.