Impact of Growth Temperature and Selenization on Dark Heat Stability in Cu(In,Ga)Se2 Solar Cells

We report the effects of two key process parameters, namely absorber growth temperature and back electrode selenization, on dark heat stability in sputter deposited Cu(In,Ga)Se
₂
solar cells. While increased growth temperature leads to larger grain size in the poly-crystalline absorber layer, it also leads to stronger Voc loss with dark heat. By reducing the selenization of the back electrode, initial Voc improves and Voc loss with dark heat can be mitigated. However, a strong reduction in Jsc is observed after subsequent light-soaking. This Jsc loss is associated with a reduction of quantum efficiency for long wavelength photons, along with a stronger increase in carrier concentration in the bulk, possibly indicating a stronger prevalence of V
_Se
-V
_Cu
divacancy defects. A barrier to forward current, observed in J-V curves taken at low temperature, increases with dark heat, indicating a possible origin of FF losses.