Characterization of window layers in CuInSe2 thin-film solar cells

Electrical and optical properties of (CdZn)S:In, (CdZn)S:In/ITO, and ZnO windows in CuInSe₂ thin-film solar cells were measured and compared to the properties of equivalent window layers deposited on glass. The resistivity and absorption edge of (CdZn)S:In films are characterized as a function of In dopant concentration and Zn content, and it is shown that the Burstein-Moss shift decreases as the Zn content is raised. Air heat treatments, used to increase V_oc and efficiency of CuInSe₂ cells, increase the resistivity and decrease the absorption edge of (CdZn)S:In window layers. CuInSe₂/ZnO cells are shown to have higher J_sc than cells with (CdZn)S windows but low V_oc and efficiency.