## 3 Results
This is due to an improved V\({}_{\text{oc}}\) from \(0.47\pm 0.02\) V to \(0.53\pm 0\) V and a significantly improved FF from \(0.38\pm 0.10\) to \(0.51\pm 0.02\). It is interesting to note that the proposed device is not able to achieve a better performance than the proposed device. \begin{table}
\begin{tabular}{c c c c c} \hline  & **PCE (\%)** & **V\({}_{\text{oc}}\) (V)** & **J\({}_{\text{sc}}\) (mA cm\({}^{-2}\))** & **FF** \\ \hline Control Devices & \(2.89\pm 0.40\) & \(0.48\pm 0.02\) & \(6.65\pm 0.30\) & \(0.45\pm 0.04\) \\
100 \(\mu\)L & \(2.24\pm 1.09\) & \(0.51\pm 0.03\) & \(4.87\pm 0.97\) & \(0.43\pm 0.12\) \\
150 \(\mu\)L & \(1.28\pm 0.53\) & \(0.39\pm 0.05\) & \(5.80\pm 1.09\) & \(0.27\pm 0.04\) \\
200 \(\mu\)L & \(3.34\pm 0.10\) & \(0.53\pm 0.00\) & \(6.09\pm 0.02\) & \(0.51\pm 0.02\) \\
250 \(\mu\)L & \(2.06\pm 0.20\) & \(0.48\pm 0.03\) & \(6.03\pm 0.55\) & \(0.36\pm 0.04\) \\
300 \(\mu\)L & \(1.24\pm 0.41\) & \(0.43\pm 0.00\) & \(5.24\pm 1.09\) & \(0.27\pm 0.03\) \\ \hline \end{tabular}
\end{table} 
Table 1: Device properties of gold chloride doped devices at different DAD volumes vs devices with no interlayer. Figure 4: (a) Atomic force microscopy (AFM) height maps of DAD films spun from different solution volumes. A spin speed of 5000 rpm was used for all films; (b) representative AFM cross sectional line graphs (each cross section is off set for clarity), and percentage height distribution plots of DAD films spun from a 300 \(\mu\)L volume at 5000 rpm. Figure 5: (a) J/V curves for the best performing device with and without a DAD interlayer; (b) J/V properties for devices with DAD interlayers spun from different solution volumes after an aqueous AuCl\({}_{3}\) treatment. that the J\({}_{\rm sc}\) is actually lower in the devices with a DAD interlayer than in the devices with no interlayer. However, the difference is less than 1 mA cm\({}^{-2}\) in values in the neighbourhood of 6 mA cm\({}^{-2}\) and thus it can be seen that the enhancements in V\({}_{\rm oc}\) and FF outweigh the decrease in J\({}_{\rm sc}\). The J/V curves for the best performing device with DAD and without are shown in Figure 4a. These curves show the difference in effect of the AuCl\({}_{3}\) dopant on the devices. For the device with no interlayer, the AuCl\({}_{3}\) improved the Jsc from 5.90 to 6.79 mA cm\({}^{-2}\) (a 15.1% improvement), improved the FF from 0.42 to 0.49 and lowered the V\({}_{\rm oc}\) from 0.51 to 0.49 V. Overall this produced a PCE gain from 2.52 to 3.24% (a 28.6% improvement). The changes exhibited in the device with a DAD interlayer were far more pronounced. The J\({}_{\rm sc}\) improved from 2.03 to 6.08 mA cm\({}^{-2}\) (a 200% improvement) while the FF increased from 0.34 to 0.53 and the V\({}_{\rm oc}\) increased from 0.43 to 0.53 V. Giving an overall PCE improvement of 0.59 to 3.44% (a 483% improvement). After AuCl\({}_{3}\) doping, the parameters for the device with the DAD interlayer are superior to the device with no interlayer, with the exception of the J\({}_{\rm sc}\). This matches the comparison seen between the average values (Table 1). Additionally, the deviation in PCE values was much smaller for the devices with the DAD interlayer than in those without, \(\pm\) 0.10% vs. \(\pm\) 0.66%. This clearly indicates that the addition of a DAD HTM improves the performance of the large area CNT/Si heterojunction solar device. The improvement because of the AuCl\({}_{3}\) treatment is largely due to an improvement in conductivity of the CNTs layer after the doping. The sheet resistance of CNTGO films before doping was \(580\pm 5\)\(\Omega\)/sq and \(199\pm 7\)\(\Omega\)/sq after doping. The improvement in conductivity is well established and due to the deposition of Au nanoparticles on the CNTs although the anions in the solution are thought to play a role as well [13; 14]. Similar effects with Pt spheres have been observed [15]. This effect should be very similar with and without the DAD present. However, there does seem to be an extra enhancement with the interlayer present.