Influence of alkali element post-deposition treatment on the performance of the CIGS solar cells on flexible stainless steel substrates

Abstract

In this study, we studied the effect of different alkali element post-deposition treatment (PDT) on the properties of CuInGaSe2 (CIGS) solar cells deposited on flexible stainless steel (SS) substrate. It is found that a certain amount of Na or K is diffused into the surface layer and inside of the CIGS absorption layer by post-deposition treatment process, which can increase the carrier concentration of the absorption layer and effectively improve the material properties of the absorption layer material, thereby improving the open circuit voltage (VOC) and fill factor (FF) of the device. Electron beam-induced current (EBIC) and Capacitance–voltage (C–V)) measurements indicated that the length of the current collection of CIGS absorption layer treated with NaF PDT and NaF + KF PDT is much larger and the total number of net carrier concentration increases significantly. This phenomenon could be attributed to the increase in carrier lifetime after the PDT treatment.