On the effect of deep defects on the Voc deficit in high-GGI CIGS absorbers: a numerical study

Using numerical simulations, we investigate the effect of a deep donor known to exist at E
_V
+ 1.33 eV, as a contribution to explain the large V
_OC
deficit of Ga-rich absorbers.. We find that uniform GGI absorbers with GGI > 0.5 suffer for the presence of this deep donor, with the V
_OC
deficit linearly increasing with GGI. On the other hand, simulations indicate that this deep donor is unlikely to be a significant performance limiter in double-graded cells.