  Alloying small quantities of silver into Cu(In,Ga)Se2 was shown to improve
the efficiency for wide and low band gap solar cells. We study low band gap
industrial Cu(In,Ga)(S,Se)2 absorbers, substituting less than 10% of the copper
with silver, using absolute photoluminescence and cathodoluminescence
spectroscopy. Silver improves the grain size and promotes the interdiffusion of
Ga and In across the depth of the absorber, resulting in a smoother band gap
gradient. However, a certain lateral inhomogeneity is observed near the front
and back sides. The non-radiative losses in the bare absorbers are reduced by
up to 30 meV.
