Investigation of traps density and position in alkali treated Cu(In,Ga)Se2 thin films and solar cells

This study contributes to the discussion on the deep traps in Cu(In,Ga)Se
₂
material with KF post deposition treatment (KF PDT). The samples were prepared on nominally alkali-free alumina substrate. In order to investigate the deep traps, capacitance-based deep level transient and optical spectroscopies (DLTS/DLOS) were performed on the samples. Two defect levels were observed at Ev+0.59eV and Ev+0.98eV. Secondary ion mass spectrometry (SIMS) profile indicated the diffusion of potassium throughout the CIGS layer. Device measurements and simulation indicate that the Ev+0.98eV play an important role in reducing efficiency for devices without KF PDT.