A chelating effect in hybrid inks for non-vacuum-processed CuInSe2 thin films

We previously demonstrated a hybrid ink consisting of synthesized Cu-Se ([Cu] > [Se]) nanoparticles and an indium (In) precursor solution to form CuInSe2 (CIS) thin films. In the precursor solution, monoethanolamine (MEA), which exhibited better performance than a different alkanolamine, triethanolamine (TEA), was used as a chelating agent to bind the In precursor and the Cu-Se nanoparticles. MEA easily forms a complex with Cu in the Cu-Se nanoparticles. To observe the effect of the Cu-MEA complex in the hybrid ink, Cu-rich Cu-Se nanoparticles were washed with MEA to reduce the Cu content in the nanoparticles through the formation of a Cu-MEA complex. As a result, CuInSe2 thin films were obtained at a fabrication temperature that was 80 degrees C lower than usual (530 degrees C). The fabricated devices made at 450 degrees C with hybrid inks of washed Cu-Se or normally synthesized Cu-Se exhibited conversion efficiencies of 5.04% and 1.04%, respectively, which confirmed that the Cu-MEA complex affected the performance of CIS solar cells that were produced with the hybrid ink process.