Comparative study of the luminescence and intrinsic point defects in the kesterite Cu2ZnSnS4 and chalcopyrite Cu(In,Ga)Se2 thin films used in photovoltaic applications

The kesterite Cu2ZnSnS4 (CZTS) is attracting considerable interest because first-principles calculations predict that its electronic properties must be similar to their associated chalcopyrite Cu(In,Ga)Se-2 (CIGS) compounds [Chen et al., Phys. Rev. B 81, 245204 (2010)]. Here, the authors report on first experimental evidence of the close resemblance in the luminescence of Cu-poor kesterites and Cu-poor chalcopyrites used in photovoltaic applications. Microluminescence measurements suggest that even the very distinct electronic structure of grain boundaries in CIGS is present, to some extent, in CZTS. The similarities between CIGS and CZTS become more pronounced as the efficiency of the CZTS solar cells gradually increases. The implications of these results for the future development of CZTS solar cells are discussed.