Comparison of Interface Characterization between Ag(In,Ga)Se2 and Cu(In,Ga)Se2 Solar Cells by High-Angle-Annular Dark-Field Scanning Transmission Electron Microscopy

The interface of Ag(In,Ga)Se2 (AIGS) and Cu(In,Ga)Se2 (CIGS) solar cells was investigated by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging method. It was found from the results that the AIGS film had Ag-rich and Ag-poor layers. The CdS layer in the CIGS solar cell had a denser structure and a better connection with the CIGS layer than the CdS layer in the AIGS solar cell. The lattice between CIGS and CdS was continuous and ordered. However, there were some defects in CdS and the lattice arrangement was distorted at the AIGS/CdS interface in the AIGS solar cell, resulting in the poor performance of the AIGS solar cell compared with the CIGS solar cell.