## 3 Results and Discussions
### Optimization of the \(InGaP/GaAs\) DjSCs with Buffer and New Top BSF Layers
#### 3.3.4 Impact of Temperature on the Performance of Solar Cells  
Temperature plays a crucial role in determining the operational characteristics and efficiency of solar cells. Numerous researchers have highlighted the profound impact of temperature on the bandgap of the solar cells [39]. Indeed, it was proven that as the temperature increases, the energy bandgap of semiconductors tends to decrease, leading to the decrease in the solar cell efficiency. The influence of the temperature on the bandgap is described using the following equation:  
\[E_{g}(T)=E_{g}(0)-\alpha\frac{T^{2}}{T+\beta} \tag{11}\]  
where \(E_{g}(T)\) is the energy bandgap of the semiconductor at temperature \(T\), the \(E_{g}(0)\) value at \(T=0\) K, and \(\alpha\) and \(\beta\) are the fitting parameters.  
Figure 14 illustrates the impact of temperature on the key performance metrics of photovoltaic (PV) solar cells. As the operating temperature rises from 300 K to 400 K, a noticeable decline in performance is observed across all parameters. The efficiency (\(\eta\)) gradually decreases, starting at a peak value of 41.585% at 300 K and dropping steadily to approximately 31.813% at 400 K, highlighting the adverse effect of high temperatures on solar cell performance.  
Similarly, the fill factor (\(FF\)) exhibits a downward trend, decreasing from 84.001% at 300 K to 80.92% at 400 K. This reduction in \(FF\) contributes significantly to the overall efficiency loss. However, the open-circuit voltage (\(V_{OC}\)) declines with increasing temperature, decreasing from 2.319 V at 300 K to 1.65 V at 400 K. This behavior is well-known in solar cells; it is primarily due to the following two key factors: an increase in carrier recombination rates, which reduces charge carrier lifetime, and a narrowing of the energy bandgap at elevated temperatures, leading to reduced voltage output.  
In contrast, the short-circuit current density (\(J_{SC}\)) experiences only a slight decline, from 21.65 mA/cm\({}^{2}\) at 300 K to 21.20 mA/cm\({}^{2}\) at 400 K, indicating that temperature has a more pronounced effect on voltage and efficiency than on current density. These trends align with previously published research [11; 40; 41; 42] reinforcing the understanding that elevated temperatures negatively impact solar cell performance, primarily through reductions in \(V_{OC}\) and efficiency \(\eta\).  
Finally, Figure 15 shows the characteristic I-V of the optimized \(InGaP/GaAs\) DJSCs investigated in this paper, which demonstrates higher key parameters. Whereas Table 8 represents a comparison between the key parameters obtained from the studied solar cell and the previous studies on DJ \(InGaP/GaAs\) DJSCs, where it can be seen clearly that the results of the investigated solar cell model in this paper has better key parameter values such as \(J_{SC}\), \(V_{OC}\), \(FF\), and \(\eta\), confirming the validity of the proposed structure configuration  
Figure 14: Performance parameters \(\eta\), \(FF\), \(J_{SC}\), and \(V_{OC}\) of the \(InGaP/GaAs\) DJSCs as a function of operating temperature.  
of the investigated solar cell in producing high electrical energy. This energy will be processed later by power electronics circuits [43; 44; 45].