Comparison of Ag(In,Ga)Se₂/Mo and Cu(In,Ga)Se₂/Mo Interfaces in Solar Cells

The structural and electrical properties of the junction at Ag(In,Ga)Se₂AIGS/Mo, and Cu(In,Ga)Se₂ CIGS/Mo layers were characterized. The region between the CIGS and Mo featured a MoSe₂ layer with a layered hexagonal structure and thickness of 10-15 nm. The c-axis of the MoSe₂ was oriented perpendicular to the Mo layer, and the c -value was 12.6 Å. However, no such layer was observed at the interface between AIGS and Mo. This result was also confirmed by energy-dispersive X-ray spectrometry and X-ray diffraction measurements of the MoSe₂ layer. The CIGS/Mo with a MoSe₂ layer formed an ohmic contact, while the AIGS/Mo without the MoSe₂ layer formed a Schottky contact. This Schottky contact showed a barrier height of 0.8 ± 0.02 eV, a nonideality factor of 1.5 ± 0.1, and a series resistance of 370 ± 8 Ω. A schematic band diagram of the AIGS/Mo junction was constructed on the basis of the above results.