Effects of oxidation and CdCl2 treatment on the electronic properties of CdTe polycrystalline films

• The hole mobility of CdTe film was found to be decreased with increasing oxygen in deposition process.
• The height of grain boundary barrier was calculated from the mobility and was found to be increased with oxidation.
• Energy band bending results from oxidation at boundary barriers was detected by XPS spectra.
• The enhancement of p-doping induced from CdCl2 annealing was detected by XPS spectra.

Electronic and structural properties of polycrystalline CdTe films which were grown at the atmosphere of vacuum, Ar, Ar/O2 mixture, by close space sublimation were studied. The effects of O2 and CdCl2 on the CdTe films were investigated from the energy band and electronic properties perspective. Based on the electrical transport measurement from 300 K to 125 K, the height of grain boundary barrier was calculated from the mobility and was found to be increased with the increasing partial pressure of O2 in CdTe deposition process. XPS spectra showed that the O–Te interaction causes the band bending downward, resulting in the increased barrier at grain boundary. XPS spectra also showed that post annealing with CdCl2 enhanced the p-doping in CdTe intensively and improved the quantum efficiency of CdS/CdTe solar cells.