# CZTSe-Based Solar Cell Performance Improvement Using the CSLO Technique
## 3 Results and Discussion
Indeed, all of the mentioned parameters are essential for measuring the quality of solar cells. In Figure 2, the External Quantum Efficiency (the ratio of the anode current to the source photo current) and the Internal Quantum Efficiency (the ratio of the anode current to the available photo current) results versus wavelength (nm) for case 1 (without the CSLO technique) and case 3 (with the CSLO technique) are represented. Figure 2 shows that in case 3, by utilizing the proposed technique, the EQE was higher than conventional solar cells made without the CSLO technique. Firstly, it was obvious that the EQE and IQE were low at short wavelengths (\(\lambda\)); as the wavelength increased, they increased dramatically to reach their maximum values. Then, the IQE remained constant at mid-range wavelengths, in contrast to the EQE. The quantum efficiency variation versus different wavelengths was directly related to the number of input photons and their energy levels in comparison to the bandgap energy of the solar cell [32]. Figure 3 illustrates the spectral response of the proposed solar cell (case 3) against the wavelength. It is obvious that the available photo current and the cathode current differed from each other at lower wavelengths due to the lower numbers of photons, but at higher wavelengths, the trends looked like each other, and the cathode current was significantly increased. Furthermore, not only was the optical behavior considerably improved, but the electrical parameters were also increased by the CSLO technique. Moreover, Table 3 illustrates a comparison of the hybrid structures, with those with that were combined with CZTSe-based solar cells having a higher efficiency than those without them. The hybrid structure with the Cu\({}_{2}\)ZnGeSe\({}_{4}\) gained the maximum value of efficiency of 50.112% while the Si-based Cu\({}_{2}\)ZnSiSe\({}_{4}\) obtained an efficiency of 33.61%, which was the lowest value. Similarly, Table 4 presents the comparison results of the proposed CZTSe-based solar cell made with the CSLO technique and other published papers with CZTSSe-based solar cells. By using the CSLO technique, the performance in comparison to conventional CZTSSe-based solar cells was significantly improved, yielding an efficiency of 32.6% and a fill factor of 79.55%. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline  & \multicolumn{2}{c}{**Case 1**} & \multicolumn{2}{c}{**Case 2**} & \multicolumn{2}{c}{**Case 3-CSLO**} & \multicolumn{2}{c}{**Case 4-CSLO**} & \multicolumn{2}{c}{**Case 5-CSLO**} & \multicolumn{2}{c}{**Case 6-CSLO**} \\ \hline Material & T & C & T & C & T & C & T & C & T & C & T & C \\ ITO & 0.03 & \(1\times 10^{19}\) & 0.03 & \(1\times 10^{19}\) & 0.02 & \(1\times 10^{19}\) & 0.02 & \(1\times 10^{19}\) & 0.02 & \(1\times  
Figure 3: Available photo current and cathode current versus optical wavelength for case 3. Figure 2: EQE and IQE vs. optical wavelength for case 1 and case 3. In addition, the results of the efficiency variation versus carrier lifetime are depicted in Figure 4. As shown in Figure 4, the efficiency was increased as a result of an increase in carrier lifetime. The value of the carrier lifetime was chosen to be similar across different layers of the proposed solar cell (100 ns) over the entire simulation. Therefore, the carrier lifetime is an important parameter in solar cell design that affects the improvement of performance as well [36; 37; 38; 39; 40]. Subsequently, the impact of the absorber thickness on the electrical properties of the proposed solar cell for case 3 by increasing the p+ layer thickness when the width of the p+ region remained unchanged and the conventional case 1 were compared together as shown in Figure 5a. As demonstrated in Figure 5a, the Jsc varied constantly when changing the absorber layer from 1 \(\upmu\)m to 4 \(\upmu\)m (increased slightly), although the V\({}_{\rm OC}\) was increased.