# Cell/Module Integration Technology with Wire-Embedded EVA Sheet
## 3 Results
Figure 10b shows the characteristics of a module manufactured by changing the diameter of the wire after fixing the number of wires to 12. The efficiency of the module with a wire diameter of 0.36 mm showed the highest efficiency. This is similar to the characteristics of the 1 \(\times\) 1 unit module. As the wire diameter increases, the contact resistivity with the finger electrode improves, resulting in a decrease in the series resistance. Consequently, the fill factor was improved. However, when compared to the 1 \(\times\) 1 unit module, as the wire diameter increases, the value of the short-circuit current significantly decreases to a greater extent. This is because it is more affected by the short-circuit current value owing to shading loss. The cell/module characteristics of the tabbing module and the wire-embedded EVA sheet module were compared. Tables 1 and 2 summarize the characteristics of the five  
Figure 10: Characteristics of a 2 \(\times\) 2-unit module based on the number of wires (**a**) and wire diameter (**b**), and SEM im-ages of wires with diameter of 0.26 mm, 0.32 mm, 0.36 mm. busbar tabbing module and wire-embedded EVA sheet module. Figure 11 shows the characteristic graph for the five-busbar tabbing module and wire-embedded EVA sheet module. For the expected power value of the 2 \(\times\) 2-unit module, the maximum value of the module characteristics was calculated based on the sum of the V\({}_{\text{oc}}\) values of the four cells, the lowest I\({}_{\text{sc}}\) value, the average value of the fill factor, and the sum of P\({}_{\text{max}}\). Table 2 lists the cell and module characteristics for the five-busbar tabbing modules, and Table 3 lists the cell and module characteristics for the wire-embedded EVA sheet module. For the FF (fill factor) value, the difference between the expected and measured values was confirmed. The reason for the decrease in the FF value in the measured value can also be explained by the increase in R\({}_{\text{s}}\). The FF can be expressed as a function of the series resistance and parallel resistance, and the series resistance can be changed by the front and rear electrodes. In particular, for the busbarless case, because the busbar, which is an important part of reducing the series resistance, is replaced or removed, the influence of the finger and the front structure on the total series resistance increases. The series resistance decreases from the expected value because of the influence of the resistivity of the wire and the contact resistance between the wire and the finger electrode, and the resistance of the ribbon to the string process of the module. The ratio of the difference between the calculated values and the measured value of power for the five-busbar tabbing module and wire-embedded EVA sheet module were 3.245% and 2.619%, respectively. As can be seen from Figure 11, it was confirmed that the power reduction characteristic of the wire-embedded EVA sheet module has a lower reduction rate of approximately 0.6% than the five-busbar tabbing module, and hence the loss when made from a cell to a module can be minimized. It was possible to manufacture a high-power module that sufficiently compensated for the disadvantages of the tabbing module. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Contact Method** & \(\mathbf{V_{oc}}\) **(V)** & \(\mathbf{I_{sc}}\) **(A)** & **FF (\%)** & \(\mathbf{P_{max}}\) **(W)** & \(\mathbf{R_{s}}\) **(f)** \\ \hline \multirow{3}{*}{Cell} & 1 & 0.672 & 9.943 & 77.352 & 5.171 & 0.007 \\  & 2 & 0.684 & 10.156 & 76.944 & 5.349 & 0.008 \\  & 3 & 0.684 & 10.195 & 76.781 & 5.351 & 0.008 \\  & 4 & 0.684 & 10.097 & 77.588 & 5.358 & 0.008 \\ \hline \multirow{3}{*}{Calculated value} & 2.724 & 9.943 & 77.166 & 21.229 & 0.031 \\  & Measured value & 2.62 & 10.297 & 77.71 & 20.54 & 0.03 \\ \cline{1-1}  & Loss ratio (\%) & \(-3.817\) & 3.56 & 0.704 & \(-3.245\) & 3.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of the five-busbar tabbing module.