Improvement of the energy conversion efficiency of Cu(In,Ga)Se2 solar cells using an additional Zn(S,O) buffer

► CuInGaSe2 solar cells were prepared with two different buffer structures. ► One sample had a CdS buffer only, and the other had a very thin CdS and Zn(S,O) buffer. ► Additional Zn(S,O) buffer was prepared by metal organic chemical vapor deposition. ► Energy conversion efficiency of the additional buffer cells was slightly improved. ► CdS/Zn(S,O) cells had higher reliability and homogeneous properties than CdS cells.