Figure 4 (a), (b) dV/d(lnI) versus I for a-Si:H(i)/MoOx/Ag and a-Si:H(i)/MoOx/ICO/Ag stacks with different electrode diameters. The arrow direction represents the electrode diameter decreasing. (c), (d) (RT-RS) versus 4/(πd2) and the corresponding linear fitting curve.
Two stacks with the architectures of c-Si(p)/a-Si:H(i)/MoOx/Ag and c-Si(p)/a-Si:H(i)/MoOx/ICO/Ag were prepared for contact resistance measurement. The measurement and fitting results were depicted in Fig. 4. The calculated ρc of the c-Si(p)/a-Si:H(i)/MoOx/Ag stack and the c-Si(p)/a-Si:H(i)/MoOx/ICO/Ag stack is 213.94 mΩ·cm2 and 191.28 mΩ·cm2, respectively. It is worth noting that Rc contains not only the contact resistance between MoOx and ICO, but the one between MoOx and c-Si(p), and also the bulk resistances of each film layers. As far as the investigated two stacks, there architectures are the same except for the ICO layer. So the difference in ρc should come from the contact resistance of MoOx/TCO and MoOx/Ag. As a conclusion, in addition to improving long wavelength response as discussed previously, adding ICO between the MoOx and the Ag electrode can reduce the contact resistance as well.