Studying effect of temperature on the efficiency of solar cells through the interpolation method

The objective of this paper is to present a comparative study between the traditional least squares method 'LSM' and the new method of "Polynomial Interpolation at Different Orders" for extracting the electrical parameters of a silicon solar cell. The focus is on the advantages and disadvantages of each approach. The results indicate that fourth-order interpolation yields the best results, but it is challenging to implement because the J-V function is neither linear nor transcendental. Therefore, we opted for the first-order Piecewise Linear Interpolation 'PLI' in the range where the J-V characteristic is nearly flat, i.e., the interval where the voltage varies from 0 to Vmax. By utilizing the first-order derivative of the function f(J, V) with two variables and MATLAB fzero function, we were able to determine the five critical parameters for our solar cell: the series resistance RS, the shunt resistance RSh, the light-generated current density Jph, the reverse saturation current density J0, and the ideality factor n. We used the Bland-Altman technique to evaluate the comparability between the two methods. The results obtained using this technique show that all the data points lie within the confidence interval. This indicates that the piecewise interpolation method provides J-V characteristic values very similar to those found by the LSM method. The strength of the new method lies in its speed, practicality, and the fact that it does not require initial values for the solar cell parameters. Additionally, it avoids the need to determine the variation intervals for each parameter and the use of complex functions such as the Lambert W function, which is necessary in the LSM method. By applying this method, we examined how the electrical parameters behave when the temperature varies from a cold region (0 °C) to a hot region (50 °C). The analysis of the results obtained by both scientific methods, namely the LSM method and polynomial interpolation, reveals a decrease in cell efficiency from 19.63 to 13.73 %. Similarly, the open-circuit voltage decreases from 0.62 to 0.524 V, and the ideality factor also decreases from 2.2 to 1.54. The current decreases from 39.50 to 34.30 mA/cm2 as the temperature increases from 0 °C to 30 °C, then stabilizes at 34.30 mA/cm2 for temperatures ranging from 30 °C to 50 °C.