## 3 Results and Discussion
While an 8.4% improvement in the I\({}_{\text{SC}}\) may seem modest, the cumulative additional energy over an expected lifetime of bPV (over 25 years) would sufficiently compensate for the additional cost of the reflector. To enhance the durability of the proposed reflector under harsh outdoor conditions for the lifetime of a BIPV, further development is required. This includes incorporating a protective layer over the silver layer and optimizing the processing temperature to improve the stability of EVA [47, 53]. In this study, we evaluated the performance of bPVs incorporating a truncated cone-shaped reflector on a single size due to the limitations in the available mold for the reflector. Future enhancements in the performance of bPVs could be achieved by further modifications to the mold of the textured reflector. Smaller textured structures in the reflector design may lead to a more diffused reflection, which could randomize the direction of reflected light and enhance bPV performance [38]. Considering the wavelength of incident light, micro-sized reflective structures are more desirable, involving complicated patterning and high temperature processes. Despite these challenges, we believe that the proposed method offers a cost-effective and viable solution for bPVs. Figure 3: I\({}_{\text{SC}}\) enhancement ratio contour plot of (**a**) the flat and (**b**) the textured reflectors under various D\({}_{\text{RR}}\)s and D\({}_{\text{Gap}}\)s.  
The ray-tracing simulation results point out that the textured reflector facilitates more photons reaching the rear side of bPVs compared to the flat reflector, aligning well with the aforementioned empirical result. The increased number of reflected photons move towards the edges of bPVs cells, thereby serving as an origin of improved ISC in the textured reflector. Figure 4 presents the rear incident electrical field intensity of the none, flat, and textured reflectors. Here, the calculation was conducted through a finite-difference, time-domain method simulation using commercially available software (Setfos 5.4, Fluxim Inc., Winterthur, Switzerland), where DRR and the DGP are 10 and 10 mm, respectively. In our simulation, we assume that the textured reflector consists of truncated cones covered by silver, whose dimension is the same as the experimentally obtained structure. The simulation result reveals that reflected light mainly converges on the edge of the rear side of bPV cells because of a self-shading effect in all cases. Notably, the intensity of rear incident light varies depending on the shape and reflectance of the rear surface. Only a limited amount of reflected light reaches the edges of cells in the case of None, due to the low reflectance of the rear glass. As the reflectance of the rear surface increases, more light redirects toward the rear side of the cells. The shape of the reflector also influences the intensity and distribution of the rear incident light. Compared to the flat reflector, the textured reflector exhibits a more successful redirection of reflected light toward the edge of the rear side of the cell, marked as enlarged red and yellow regions at the cell's edges (Please see Figure 4c). The calculated sum of electric field distribution in the rear side of the textured reflector is 4.5% higher than that of the flat reflector, which is slightly higher than the experimental data. We believe that the small discrepancy between the experimental and simulation results might be caused by the flatness of the rear reflector. Furthermore, the enhanced rear incident light is theoretically calculated at the center of bPVs in the case of the textured reflector, revealing that the suggested texture reflector is more effective in randomizing the trajectory of reflected light. These findings indicate that the textured reflector provides randomly distributed reflected light with high intensity to bPVs, offering potential benefits such as increased ISC and reduced current mismatch among cells.