The effect of Cu-Zn disorder on charge carrier mobility and lifetime in Cu2ZnSnSe4

Cu-Zn disorder is one possible origin for the limited efficiencies of kesterite solar cells and its impact on the band gap and band tails have been intensively studied. However, the effect on charge transport and recombination, which are key properties for solar cells, has not been investigated so far. Therefore, we probe the impact of the Cu-Zn order on charge carrier mobility and lifetime. To this end, we change the Cu-Zn order of a co-evaporated Cu2ZnSnSe4 thin film by sequential annealing and probe the impact by time-resolved terahertz spectroscopy. Aside from of the well-known band gap shift, we find no significant change in mobility and lifetime with Cu-Zn order. This finding indicates that Cu-Zn disorder is not limiting efficiencies of kesterite solar cells at their current status by means of charge carrier recombination and transport.