## 2 Materials and Methods  
### Construction of the C3 PV Module under Test  
The appearance and internal connection structure of 200 three-junction (3) cells are shown in Figure 1. This is a specific arrangement in which the cells are divided into four parallel connected rows of 50 cells each, and none of the connections intersect. A C3 PV module with this design was chosen as an example for the developed simulation method and its initial verification.  
Table 2 shows the basic parameters of the tested C3 PV module as given by the manufacturer. These parameters are given under non-standard test conditions, called standard test conditions (STCs). According to the manufacturer, the rated parameters given in the datasheet and nameplate were tested for solar irradiance 850 W/m\({}^{2}\), cell temperature 25 \({}^{\circ}\)C, and AM 1.5.  
Figure 1: Appearance and design of internal cell connections in CX-75/200 module.  
Figure 2 presents a model of the structure of a single three-junction cell, which considers the ranges of absorbed radiation for three successive layers of semiconductors. Figure 2 gives the values of \(E_{g}\) energy gaps for each layer and the percentage of absorbed energy reaching the cell in the form of concentrated solar radiation. The operating principle of this type of cell is that the size of the energy gap (\(E_{g}\)) decreases in the direction consistent with the penetration of radiation. The purpose of building such structures is to absorb the broadest possible spectrum of solar radiation reaching the outer surface of the module.  
The type of PV cell (3J) is designed to capture the maximum possible sunlight (300-1800 nm) as opposed to standard PV cells (only 350-1100 nm). The standard spectrum of solar radiation, which can theoretically be described by-laws (Planck, Stefan-Boltzmann, and Wien), is never fully utilized by photovoltaic cells. Multilayer modules broaden the absorbed spectrum, and the concentration of radiation multiplies this effect. The spectral ranges of solar radiation absorbed by individual layers of the cell under consideration are marked in Figure 2. The different materials in a three-junction cell are arranged so that each  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter Name** & **Module C3 PV: CX-75/200** \\ \hline Cell type & three-junction \\ Number of cells, pcs. & 200 \\ Cell size \(d\), mm & 3 \\ Concentrator type & Fresnel spot-focusing \\ Maximum power \(P_{MPP}\), W & \(75\pm 10\%\) \\ Open-circuit voltage \(U_{OC}\), V & 152 \\ Voltage to MPP \(U_{MPP}\), V & 138 \\ Short-circuit current \(I_{SC}\), A & 0.58 \\ Current for MPP \(I_{MPP}\), A & 0.54 \\ Temperature coefficient, \(\%/^{o}\)C & \(-0.15\) \\ Maximum operating temperature above ambient & 55 \\ temperature, \({}^{o}\)C & 1000 \\ Maximum system operating voltage \(U_{MAX}\), V & \(828\times 428\times 82\) \\ Dimensions, mm & \(9.4\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Nominal parameters of CX-75/200 module [21].  
Figure 2: Structure and equivalent model of a single 3J cell and the ranges of absorbed radiation.  
material absorbs a specific range of sunlight. C3 PV cells absorb approx. 44% of photons from sunlight, while a regular PV cell can do the same with 15-20% efficiency.  
Figure 3 shows the radiation distribution patterns for an incident angle of radiation deviated from the perpendicular to the surface of a classical PV module (Figure 3a) and the operating principle of a point-focused Fresnel concentrator (Figure 3b). The diagram shown in Figure 3b indicates the limited range of angle (\(\pm\Delta\theta\)) of incidence of radiation that can fall in the C3 PV cell area. A larger deviation of the incident angle causes the radiation to fall outside the C3 PV cell area.