Heterointerface recombination of Cu(In,Ga)(S,Se) 2 ‐based solar cells with different buffer layers

Cu(In,Ga)(S,Se) 2 solar cell is high conversion efficiency ( η ) thin‐film solar cell. One of the methods to further increase the η is to replace traditional CdS/ZnO buffer layers by more transparent materials to enhance carrier generation in spectral region from 330 to 550 nm. Cd 0.75 Zn 0.25 S/ZnO, thin CdS/ZnS(O,OH)/ZnO, and thin CdS/ZnS(O,OH)/Zn 0.79 Mg 0.21 O buffer layers are therefore developed to replace the traditional CdS/ZnO buffer layers in Cu(In,Ga)(S,Se) 2 ‐based solar cells. ZnO, Zn 0.79 Mg 0.21 O, and ZnO:Al are prepared by sputtering method. Low‐surface carrier recombination, caused by low sputtering damage, is observed in the solar cells with CdS/ZnO or Cd 0.75 Zn 0.25 S/ZnO buffer layers, while the highest surface carrier recombination is presented in the solar cell with ZnS(O,OH)/ZnO buffer layer. Therefore, thin CdS/ZnS(O,OH)/ZnO or Zn 0.79 Mg 0.21 O buffer layers are applied in the solar cells to decrease surface recombination (reduced sputtering damage). Ultimately, conversion efficiencies of the solar cells with Cd 0.75 Zn 0.25 S/ZnO, thin CdS/ZnS(O,OH)/ZnO, and thin CdS/ZnS(O,OH)/Zn 0.79 Mg 0.21 O buffer layers are enhanced to 19.61, 18.60, and 18.81%, respectively, which are higher than that of 18.32% for the solar cell with the traditional CdS/ZnO buffer layers.