An investigation on performance enhancement for KF post deposition treated CIGS solar cells fabricated by sputtering CIGS quaternary targets

Copper Indium Gallium Selenide (Cu(In,Ga)Se2, CIGS) absorbers were fabricated by sputtering from quaternary CIGS targets and post-selenization. Potassium (K) was doped into absorbers by potassium fluoride post deposition treatment (KF-PDT). The performances of cells and the concentration distribution of alkali elements were investigated. Recombination of CIGS cells was also detected. The introduction of K led to an increase in efficiency from 11.1% for K-free cells to 14.9% for K-doped cells, with higher open-circuit voltage (Voc). For depth profile of alkali elements in absorbers, the content of Na decreased and the content of K increased after KF-PDT. The decrease of interface recombination at CIGS/CdS interfaces is considered to be the reason for the enhanced efficiency.