## 3 Results and Discussion  
Figure 2 illustrates the I-V characteristics of a bifacial PV module depicted with and without a reflector, considering varying distances between the cell and the reflector (D\({}_{\text{RR}}\) \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{\(\mathbf{D_{Gap}}\) (mm)} & 5 & 7.5 & 10 & 12.5 \\ \hline Configuration & & & & \\ \hline A\({}_{\text{Cell}}\) (mm\({}^{2}\)) & 2500 & 2500 & 2500 & 2500 \\ \hline A\({}_{\text{Gap}}\) (mm\({}^{2}\)) & 525 & 806 & 1100 & 1406 \\ \hline A\({}_{\text{Gap}}\)/A\({}_{\text{Cell}}\)+A\({}_{\text{Gap}}\) (\%) & 17.3\% & 24.3\% & 30.5\% & 36\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The configuration of bPVs with various D\({}_{\text{Gap}}\). 10-30 mm) and cell gap widths (D\({}_{\text{Gap}}\): 5-12.5 mm). The short-circuit current (I\({}_{\text{SC}}\)) of bPVs is normally the sum of the current generated from the front (I\({}_{\text{front}}\)) and the rear (I\({}_{\text{rear}}\)) incident light, as follows:  
\[ \begin{split}\text{I}_{\text{SC}}=\text{I}_{\text{front}}+\text{I }_{\text{rear}}=\int\text{A}_{\text{Cell}}\times\phi_{\text{Front}}(\lambda) \times\text{EQE}_{\text{Front}}(\lambda)\text{d}\lambda+\int\Bigl{(}1-\eta_{ \text{shading}}\Bigr{)}\times\\ \text{A}_{\text{Gap}}\times\phi_{\text{Gap}}(\lambda)\times\text{R }(\lambda)\times\eta_{\text{Dpt}}\times\text{EQE}_{\text{rear}}(\lambda) \text{d}\lambda\end{split}  \tag{1}\]  
where the \(\Phi_{\text{Front}}(\lambda)\) and \(\Phi_{\text{Gap}}(\lambda)\) represent the photon flux irradiating the front of the bifacial photovoltaic cell and the gap between cells, respectively, and are equal under a solar simulator. \(\text{EQE}_{\text{Front}}(\lambda)\) and \(\text{EQE}_{\text{rear}}(\lambda)\) denote the external quantum efficiency of the bPV when illuminated from the front and the rear, respectively. \(\eta_{\text{shading}}\) is the loss ratio due to self-shading from the cell and mask. \(\text{R}(\lambda)\) is the reflectance of the rear reflector, and \(\eta_{\text{Opt}}\) is the efficiency of the reflected light that reaches the rear surface of the bPV [6; 49]. In this study, we assume that the \(\text{EQE}_{\text{Rear}}(\lambda)\) is 0.7 times of \(\text{EQE}_{\text{Front}}(\lambda)\) considering the bifaciality of the cell. In addition, the \(\text{R}(\lambda)\) is set to 0.8 for all cases based on the reflectance spectrum of the reflectors used. While the I\({}_{\text{front}}\) remains constant regardless of a rear reflector, the I\({}_{\text{rear}}\) varies depending on the module configuration (A\({}_{\text{Gap}}\): 17-36%) and rear reflector conditions (\(\eta_{\text{shading}}\) and \(\eta_{\text{Opt}}\)). We set the \(\eta_{\text{shading}}\) as 0.2 (D\({}_{\text{Gap}}\) = 10 mm and D\({}_{\text{RR}}\) = 30 mm)-0.8 (D\({}_{\text{Gap}}\) = 5 mm and D\({}_{\text{RR}}\) = 10 mm), considering the dimension of bPVs used in the experiment. In the case of a bPV with its rear surface covered by black paper (None), consistent short-circuit current (I\({}_{\text{SC}}\)) and power conversion efficiency (PCE) values were observed, irrespective of changes in D\({}_{\text{RR}}\) and D\({}_{\text{Gap}}\). In this configuration, the I\({}_{\text{rear}}\) is nearly negligible due to the very low R(\(\lambda\)), leaving I\({}_{\text{SC}}\) primarily governing the I\({}_{\text{front}}\). Thus, the I\({}_{\text{SC}}\) and PCE of the none group ranged from 0.97 to 0.99 A and 17.6 to 18.2%, respectively, in all scenarios, indicating that the I\({}_{\text{front}}\) of the bPV is approximately 0.98 A (current density of 39.2 mA/cm\({}^{2}\)).