Electrical properties of CIGS/Mo junctions as a function of MoSe 2 orientation and Na doping

The electrical properties of Cu(In,Ga)Se 2 /Mo junctions were characterized with respect of MoSe 2 orientation and Na doping level using an inverse transmission line method, in which the Cu(In,Ga)Se 2 (CIGS)/Mo contact resistance could be measured separately from the CIGS film sheet resistance. The MoSe 2 orientation was controlled by varying the Mo surface density, with the c ‐axis parallel and normal orientations favored on Mo surfaces of lower and higher density, respectively. The effect of Na doping was compared by using samples with and without a SiO x film on sodalime glass. The conversion of the MoSe 2 orientation from c ‐axis normal to parallel produced a twofold reduction in CIGS/Mo contact resistance. Measurements of the contact resistances as a function of temperature showed that the difference in CIGS/Mo contact resistance between the samples with different MoSe 2 orientations was due to different barrier heights at the back contact. Comparison between Na‐doped and Na‐reduced samples revealed that the contact resistance for the Na‐reduced system was four times of that of the doped sample, which showed more pronounced Schottky‐junction behavior at lower temperature, indicating that Na doping effectively reduced the barrier height at the back contact.