Optical Characterization of Defects in High-efficiency (Ag,Cu)(In,Ga)Se2

We applied time-resolved photoluminescence (TRPL) spectroscopy to study optimized chalcopyrite (Ag,Cu)(In,Ga)Se
₂
thin films. The device shows power conversion efficiency of 18.7%. The metastable defect V
_Se
-V
_Cu
within ACIGS at Ev+0.98 eV is detected in sub-bandgap TRPL excitation spectra. TRPL lifetime of 50 ns is limited by the density of mid-gap defects such as Cu
_Ga
or Cu
_In
. The similarity of TRPL dynamics before and after light soaking indicates the optimized ACIGS thin film is less metastable because the density of V
_Cu
-V
_Se
defect is reduced to below 10
¹⁵
cm
^-3
. This study indicates that ACIGS has improved cell efficiency and reliability characteristics.