The authors studied the nonradiative recombination in a kesterite mineral CZTS via an anion vacancy. They performed a series of first-principles simulations to show that a neutral sulphur vacancy extends the carrier lifetime in CZTS, while a charged one is the source of the recombination. The latter result agrees well with previous studies, however, the longer lifetime with a defect is unconvining.
First, the paper presented several orders of magnitude shorter lifetimes as compared to experimental measurements due to the small simulation cells as the authors stated in the manuscript. The authors should provide evidence to support that their conclusion would still hold in a realistic simulation cells.
Unlike molecular systems, concentrations of minority and majority carrier can differs significantly,
and often the minority carrier lifetime dominates the recombination process in photovoltaics.
The manuscript doesn't show how the carrier concentrations are incorporated in their method.
Considering the size of the simulation cell, the carrier concentration would be much higher than the concentrations relevent to the experiments.
I recommend the authors to estimate the effect of the carrier concentration on the lifetime.