## 6 Conclusions  
There has been an increasing demand to be able to model the performance and predict the amount of energy that could be generated from any solar PV cell. As a result of this, equivalent circuits of PV cells have been developed as well as other mathematical models to attempt to predict the performance characteristics and potential output power of a PV cell by many researchers. This paper discussed a MATLAB code's performance, which was developed to simulate the I-V and P-V characteristics of the RADTIRC-PV structure. This paper also proposed and demonstrated for the first time the angular response of a CPV was simulated using MATLAB and the simulation results were verified through the experiment.  
The performances of the RADTIRC-PV structure and the bare PV cell were simulated under STCs at different incident angles ranging from \(-50^{\circ}\) to \(50^{\circ}\) and the results were compared with the ones obtained from indoor experiments. The simulation values of the short circuit current agreed well with the experiment values for the RADTIRC-PV structure, with the maximum relative error of 2.1229% obtained at the incident angle of \(\pm 10^{\circ}\). For the  
Figure 12: Comparison of the opto-electronic gains obtained from simulations and experiments for the RADTIRC-PV structure and a bare PV cell at STCs.  
open-circuit voltage, the highest relative error of 5.3913% achieved at the incident angle of \(\pm\)50\({}^{\circ}\). The maximum power's simulation values achieved the highest relative error of 9.9681% logged at the incident angle of \(\pm\)50\({}^{\circ}\) when compared with the experimental value. Looking at the fill factor's simulation values, the highest relative error of 4.4231% recorded at the incident angle of \(\pm\)50\({}^{\circ}\) when compared with the experimental value. As for the opto-electronic gain, no error was recorded when the simulation was compared with the experiment. Further research needs to be carried out to determine the cause of peak error occurrences at specific incident angles. It can be concluded that the simulation model is able to predict the I-V and P-V characteristics of the RADTIRC-PV structure with good accuracy when compared with the experiment. It is expected the development of this code will enable the stakeholders to compute the I-V and P-V characteristics of any CPV as well as predicting the angular response of the CPV in a short period of time.  
Conceptualisation, F.M.-S.; Data curation, F.M.-S.; Formal analysis, F.M.-S., S.H.A.-B. and C.K.; Funding acquisition, F.M.-S., S.H.A.-B., J.A.A.-R., M.N.M. and N.A.B.; Investigation, F.M.-S., S.H.A.-B. and C.K.; Methodology, F.M.-S.; Project administration, F.M.-S.; Resources, F.M.-S.; Software, F.M.-S. and N.S.; Supervision, F.M.-S.; Validation, F.M.-S., S.H.A.-B. and N.S.; Visualization, F.M.-S. and S.H.A.-B.; Writing-original draft, F.M.-S., S.H.A.-B., N.S. and C.K.; Writing-review & editing, F.M.-S., H.F., S.H.A.-B., J.A.A.-R., N.S., C.K., M.N.M., N.A.B. and M.Z. and All authors have read and agreed to the published version of the manuscript.  
The authors would like to thank Edinburgh Napier University for the Research Excellence Grant (REG) under the SEBE SEED-Corn fund and the Universiti Teknologi Malaysia for the Visiting Researcher (Publication) scheme (Q.J090000.21A4.00D20). The Article Processing Charges (APC) is funded by Agencia Nacional de Investigacion y Desarrollo (ANID) through the projects Fondecyt regular 1200055 and Fondef ID19I10165 and by the Universidad Tecnica Federico Santa Maria (UTFSM) through the project PI_m_19_01.  
Raw data can be obtained by contacting the lead author [PERSON].  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.