## 3 Simulation Results
Figure 7a shows the calculated J-V characteristics of a CIGS solar cell depending on the equispaced phase thickness of the EPL. In addition, the ETAM-applied J-V curve, where the ETAM-applied generation rate was used in the electrical modeling, was also plotted along the red dotted line. None of the eleven calculation results of the J-V curves can be distinguished in Figure 7a due to their extremely small differences at this J-V scale. In the ETAM-applied J-V curve, the calculated values of J\({}_{\text{SC}}\) and V\({}_{\text{OC}}\) were \(-34.0\) mA/cm\({}^{2}\) and \(0.81\) V, respectively, which were close to other calculation results of J\({}_{\text{SC}}\) and V\({}_{\text{OC}}\) in a similar CIGS solar cell structure [25]. A close view of the J-V characteristics at near the zero applied voltage is shown in Figure 7b. The deviation of J\({}_{\text{SC}}\) calculated between the coherent and ETAM-applied models lies within the range of \(-0.54\%\) to \(+0.54\%\), which was close to the \(-0.67\%\) to \(+0.9\%\) deviation obtained by the aggregate sums of the electron-hole pair generation rates between the coherent and ETAM-applied models. In addition, the maximal deviation of V\({}_{\text{OC}}\) was as small as \(\pm 0.017\%\), which was ascribed to the fact that V\({}_{\text{OC}}\) has a logarithmic dependence on the carrier density [26]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **n-ZnS** & **p-CIGS** \\ \hline Dielectric constant, \(\varepsilon_{r}\) & 8.28 & 13.60 \\ Band gap, \(Eg\) (eV) & 3.68 & 1.21 \\ Electron affinity, \(\chi_{e}\) (eV) & 4.13 & 4.21 \\ Valence band effective density of states, \(N_{b}\) (cm\({}^{-3}\)) & \(2.4\times 10^{19}\) & \(1.6\times 10^{19}\) \\ Conduction band effective density of states, \(N_{c}\) (cm\({}^{-3}\)) & \(1.7\times 10^{18}\) & \(2\times 10^{18}\) \\ Electron mobility, \(\mu_{n}\) (cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\)) & 250 & 100 \\ Hole mobility, \(\mu_{p}\) (cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\)) & 70 & 25 \\ Electron lifetime, \(\tau_{n}\) (s) & \(2\times 10^{-8}\) & \(1\times 10^{-18}\) \\ Hole lifetime, \(\tau_{p}\) (s) & \(6\times 10^{-8}\) & \(5\times 10^{-8}\) \\ Donor concentration, \(N_{d}\) (cm\({}^{-3}\)) & \(5\times 10^{16}\) & - \\ Acceptor concentration, \(N_{a}\) (cm\({}^{-3}\)) & - & \(3\times 10^{16}\) \\ Radiative recombination rate, \(R_{B}\) (cm\({}^{-3}\) s\({}^{-1}\)) & \(10^{-10}\) & \(10^{-10}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters used in the electrical modeling [24]. Figure 6: (**a**) Spectral irradiance of air mass (AM) 1.5 sunlight ranging between 300 and 1100 nm used in this calculation. (**b**) Calculated spatial profiles of the generation rate in the longitudinal z-direction \(G(z,t_{b})\) with respect to 10 different equispaced phase thicknesses of \(t_{1}\), \(t_{2}\),... and \(t_{10}\). The ETAM-applied generation rate in the longitudinal z-direction \(G^{ETAM}(z)\) was plotted along the red dotted line. The generation rate was obtained by integrating the optical power dissipation weighted by the spectral irradiance of AM 1.5 sunlight. It is notable that the \(\pm 0.54\%\) maximal percent deviation of J\({}_{\rm SC}\) can be understood to be the inaccuracy of the calculation when a thick cover glass layer was inappropriately modeled as a coherent layer. An arbitrarily determined thickness of the coherently modeled cover glass can provide a random optical phase change ranging between 0 and 2\(\pi\).