## 4 Simulation Process  
A MATLAB code was developed to envisage the electrical power output produced from the RADTIRC-PV structure using Equations (1)-(6). The code was developed to simulate the angular characteristics of the RADTIRC-PV structure from \(-50^{\circ}\) to \(50^{\circ}\) with an increment \(5^{\circ}\). Figure 4 demonstrates the steps needed to produce the I-V and P-V curves at each incident angle. A \(0^{\circ}\) incident angle means that the sun rays are perpendicular to the RADTIRC. The range of incident angle (\(\pm 50^{\circ}\)) was selected to demonstrate that the RADTIRC is capable of capturing the sun rays within its acceptance angle of \(\pm 40^{\circ}\)  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Value** \\ \hline Solar radiation intensity, \(\rm G_{ref}\) & \(1000\) W/m\({}^{2}\) \\ Reference Temperature, \(\rm T_{ref}\) & \(25\ ^{\circ}\)C \\ Square solar cell area, A & \(1\ \rm cm^{2}\) \\ Short circuit current, \(\rm I_{sc}\) (at \(0^{\circ}\)) & \(0.0350\) A \\ Open-circuit voltage, \(\rm V_{oc}\) (at \(0^{\circ}\)) & \(0.586\) V \\ Ideality factor, n & \(1.109\) \\ Energy bandgap, \(\rm E_{g}\) & \(1.12\) \\ Charge of an electron, \(\rm q\) & \(1.6\times 10^{-19}\) C \\ Boltzmann constant, \(\rm k\) & \(1.38\times 10^{-23}\) m\({}^{2}\) kg s\({}^{-2}\) K\({}^{-1}\) \\ Series resistance, \(\rm R_{s}\) & \(0.047994\)\(\rm\Omega\) \\ Shunt resistance, \(\rm R_{sh}\) & \(2148.53\)\(\rm\Omega\) \\ Short circuit current temperature coefficient, \(\alpha\) & \(0.00024\) A/\({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parametric values of the solar cell.  
The code takes into account several parameters e.g., solar irradiance, opto-electronic gain (Equation (1)) and the key parameters of the solar PV cell. The code then calculate analytically the value of \(I_{ph}\), \(I_{s}\) and \(I_{s}\).  
Afterwards, by evaluating Equations (4)-(6) and substituting back into Equation (3) and using [PERSON] iteration method, the corresponding I value is obtained for voltages ranging from 0 to V\({}_{oc}\). The corresponding value of power, P is calculated by multiplying the corresponding values of I and V. The I-V and P-V curves are then plotted at the end of the programme. In each simulation, the I-V and P-V characteristics were produced, and the short circuit current (\(I_{sc}\)), the open-circuit voltage (V\({}_{oc}\)), the maximum power (P\({}_{max}\)), the fill factor (FF) and the opto-electronic gain (C\({}_{opto-e}\)) were determined and recorded.  
The I-V and P-V characteristics generated from the simulations were compared with values obtained from the experiment described in Section 3.1. The relative error, RE for the each reading is calculated using the formula presented in Equation (7) [62] where \(t_{s}\) and \(t_{exp}\) are the simulation and experimental values respectively. Tables A1-A4 in the Appendix demonstrated the comparison of simulation and experimental values (short circuit current, open circuit voltage, maximum power, fill factor, opto-electronic gain and the relative error) for the RADITRC-PV structure and the bare PV cell.  
\[RE=\left|\frac{t_{s}-t_{exp}}{t_{s}}\right|\times 100\% \tag{7}\]