Contactless characterization of metastable defects in Cu(In,Ga)Se₂ solar cells using time-resolved photoluminescence

The authors present a contactless optical characterization method for the study of metastable defects in Cu(In,Ga)Se₂ solar cells. A methodology for the analysis of time-resolved photoluminescence (TRPL) signals is presented. It leads to the observation of a hysteresis phenomenon regarding the minority carrier dynamics following the activation of the metastable defects. The amplitude of the hysteresis phenomena was compared between CIGS solar cells with different absorber/buffer layer interface properties. It is in these particular spatial regions where the metastable defects can be mostly found. The developed contactless characterization method was compared with classical current-voltage measurements. TRPL leads to a more complete understanding of the physics of metastable defects in terms of quantifying the shift in minority charge carriers dynamics that it induces.