## 3 Results
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Reaction**} & \multirow{2}{*}{**ZnO NRs**} & \multirow{2}{*}{**Reflectance**} & \multicolumn{6}{c}{**Simulated PV Properties**} \\ \cline{3-10}  & & & **I\({}_{\text{sc}}\) (\(\mu\)m)** & & **I\({}_{\text{sc}}\) (\(\lambda\))** & **V\({}_{\text{oc}}\) (\(V\))** & **I\({}_{\text{max}}\) (\(\lambda\))** & **V\({}_{\text{max}}\) (\(V\))** & \
\begin{tabular}{c} **Fill** \\ **Factor** \\ \end{tabular} &
\begin{tabular}{c} **Efficiency** \\ **(\%)** \\ \end{tabular} \\ \hline
3 & 0.75 & 12.360 & 0.4803 & 0.5889 & 0.455443 & 0.505304 & 81.36 & 14.38 \\
4 & 1.00 & 12.690 & 0.4796 & 0.5886 & 0.454993 & 0.504741 & 81.35 & 14.35 \\
5 & 1.10 & 9.580 & 0.4970 & 0.5894 & 0.469686 & 0.507107 & 81.31 & 14.88 \\
6 & 0.90 & 14.95 & 0.4653 & 0.5870 & 0.441221 & 0.503526 & 81.34 & 13.88 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of optical and PV properties of ZnO NRs AR-based Si solar cells (PC1D simulation). Figure 7: (**a**) Refractive index and (**b**) extinction coefficient plots of the bare Si wafer, textured Si wafer, and vertically arranged ZnO NRs on textured Si wafers. To explain the good PCE and photocurrent of Si solar cells based on ZnO NRs AR, the diffusion coefficient and diffusion length are the critical factors, as they are associated with charge carrier transport upon light illumination [41]. It is known that the shorter diffusion length results in a high recombination rate [41]. Figure 9 depicts the plot of diffusion length and distance from the front of the AR, obtained by PC1D simulation. In all lengths of ZnO NRs AR, the diffusion lengths gradually increased up to 100 \(\upmu\)m. Afterward, a saturation in diffusion length was obtained with the increase of distance from the front. This observation clearly deduces that the maximum limit of the diffusion length is 100 \(\upmu\)m for all lengths of ZnO NRs, as illustrated in Figure 9. In this calculation, the thicknesses of the emitter regions are 15 \(\upmu\)m, 24 \(\upmu\)m, 24.78 \(\upmu\)m, and 30 \(\upmu\)m for 0.75 \(\upmu\)m, 0.9 \(\upmu\)m, 1.0 \(\upmu\)m, and 1.1 \(\upmu\)m lengths of ZnO NRs AR, respectively. From Figure 9, the ratios of the diffusion length to the thickness of the emitter are 6.66, 4.16, 4.03, and 3.33 for 0.75 \(\upmu\)m, 0.9 \(\upmu\)m, 1.0 \(\upmu\)m, and 1.1 \(\upmu\)m lengths of ZnO NRs, respectively. The lowest ratio value is related to a high penetration of dopant in the emitter. Moreover, the probability of charge collection at the interface of the N and P layers is linked with the diffusion length and size of the device, especially the emitter size [42]. Suppose the thickness of the emitter is lower than the diffusion length, which results in a considerably high charge collection probability. As represented in Figure 9, the high diffusion length obtained by ZnO NRs AR is attributed to a higher probability of charge collection, resulting in the large collection of light-generated charge carriers at the p-n junction and high conduction to the cell. Hence, this simulation study reflects that the  
Figure 8: (**a**) I-V curve with a power curve and (**b**) incident photon-to-electron conversion efficiency (IPCE) curve of Si solar cells based on ZnO NRs antireflection (AR). low-temperature solution method is highly feasible for growing vertically arranged ZnO NRs AR to fabricate the Si wafer-based solar cells.