## 3 Results and Discussion
Under the same D\({}_{\text{RR}}\) and D\({}_{\text{Gap}}\) conditions, the flat reflector achieves a PCE of 19.2%, an I\({}_{\text{SC}}\) of 1.033 A, and an \(\eta_{\text{Opt}}\) of 0.37. The textured reflector directs more photons to the rear side of the bPV, leading to a 7.6% improvement in I\({}_{\text{SC}}\), as shown in Figure 2d. This result indicates that the textured reflector enables unabsorbed light to be recycled by guiding it to the rear side of the bPVs. However, the narrow D\({}_{\text{Gap}}\) (<5 mm) limits the impact on the reflector due to the lack of passing photons. As illustrated in Figure 2a,b, the I\({}_{\text{SC}}\) improvement ratio arising from incorporating textured and flat reflectors into the bPV with a D\({}_{\text{Gap}}\) of 5 mm is less than 1.5%. We believe this reduced enhancement is primarily due to self-shading and lower incident light from the narrow A\({}_{\text{Gap}}\). Moreover, as most of the light rebounding to the rear side of the bPVs comes from near the cell regardless of reflector type, the impact of the proposed textured reflector on the bPV is not distinctive in the bPVs with small D\({}_{\text{Gap}}\)[49; 50; 51; 52]. This suggests that the proposed system is particularly beneficial for BIPV applications, where the larger D\({}_{\text{Gap}}\) maximizes the reflector's effect, while the impact of the rear reflector is diminished in field-installed PVs due to the reduced D\({}_{\text{Gap}}\). Thus, while the textured reflector significantly enhances the PCE of bPVs designed for BIPVs, its effect is constrained when the D\({}_{\text{Gap}}\) is small. To quantify the impact of the textured reflector on the performance of bPV for BIPVs, we analyzed its I-V characteristics under various D\({}_{\text{RR}}\)s and D\({}_{\text{Gap}}\)s in three cases: the None,the Flat, and the Textured reflectors. Figure 3 shows contour plots of the I\({}_{\text{SC}}\) improvement ratio for the flat and the textured reflectors. Here, the I\({}_{\text{SC}}\) enhancement ratio is derived by dividing the I\({}_{\text{SC}}\) of a bPV with the reflector by the I\({}_{\text{SC}}\) of a bPV without the reflector (the none group). For both flat and textured reflectors, no significant enhancement ratio in I\({}_{\text{SC}}\) is observed when the D\({}_{\text{RR}}\) and D\({}_{\text{Gap}}\) are small. This is primarily attributed to a reduction in transmitted photons through the gap between the cells and the self-shading from the mask and the cells. However, as the D\({}_{\text{RR}}\)s and D\({}_{\text{Gap}}\) increase, the enhancement ratio boosts in the cases of the flat and the textured reflectors. Notably, the textured reflector exhibits a higher enhancement ratio and reaches a saturation point at a higher value compared to the flat one. Specifically, the flat reflector demonstrates an I\({}_{\text{SC}}\) improvement ratio of 4.8% where the D\({}_{\text{RR}}\) and the D\({}_{\text{Gap}}\) are 30 and 12.5 mm, respectively. Despite the enlarged A\({}_{\text{Gap}}\), the \(\eta_{\text{Opt}}\) decreases to 0.29. Furthermore, its enhancement ratio is saturated by approximately 5% despite the elongated D\({}_{\text{RR}}\) and the enlarged D\({}_{\text{Gap}}\). No additional improvement was observed in the flat reflector when the D\({}_{\text{RR}}\) was higher than 20 mm and the D\({}_{\text{Gap}}\) was larger than 10 mm due to a trade-off relationship between A\({}_{\text{Gap}}\) and \(\eta_{\text{Opt}}\). On the other hand, the I\({}_{\text{SC}}\) enhancement ratio of the textured reflector continuously increases, reaching over 8.4% where the D\({}_{\text{RR}}\) and D\({}_{\text{Gap}}\) are 30 and 12.5 mm, respectively. The calculated \(\eta_{\text{Opt}}\) was 0.51, which is similar to that of the textured reflector with 10 mm of D\({}_{\text{Gap}}\). Additionally, employing the suggested textured reflector with D\({}_{\text{RR}}\) = 20 mm and D\({}_{\text{Gap}}\) = 10 mm achieves an enhancement ratio of 6%, which is 2.0% higher than that of the flat reflector.