Effects of combined additional indium deposition and potassium fluoride post-deposition treatments on Cu(In,Ga)Se2 thin film solar cells

The effect of additional indium on copper indium gallium selenide (CIGS) thin films and solar cells was investigated with respect to potassium fluoride post-deposition treatment (KF-PDT) using current-voltage, external quantum efficiency, scanning electron microscopy, X-ray photoelectron spectroscopy, time-resolved photoluminescence and capacitance-voltage measurements. The cell performance, particularly open-circuit voltage (Voc) improved drastically by the combined treatments of additional indium deposition after CIGS growth and subsequent KF-PDT. A Cu deficient layer at the CIGS surface increased after both treatments rather than only KF-PDT. Photoluminescence intensity, lifetime and net carrier concentration of KF-untreated CIGS solar cells did not change significantly by only additional indium deposition. However, they improved because of the combined treatments.