  Cu2ZnSnS(e)4 (CZTS(e)) solar cells have attracted much attention due to the
elemental abundance and the non-toxicity. However, the record efficiency of
12.6% for Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is much lower than that of
Cu(In,Ga)Se2 (CIGS) solar cells. One crucial reason is the recombination at
interfaces. In recent years, large amount investigations have been done to
analyze the interfacial problems and improve the interfacial properties via a
variety of methods. This paper gives a review of progresses on interfaces of
CZTS(e) solar cells, including: (1) the band alignment optimization at
buffer/CZTS(e) interface, (2) tailoring the thickness of MoS(e)2 interfacial
layers between CZTS(e) absorber and Mo back contact, (3) the passivation of
rear interface, (4) the passivation of front interface, and (5) the etching of
secondary phases.
