Ideal Solar Cell Electrical Parameters and Ideality Factor Effect on the Efficiency

Abstract

The determination of the electrical conversion efficiency (η<SUB>C</SUB>) is particularly important to evaluate the performance of a solar cell. For the evaluation of the efficiency by considering the ideal solar cell characterized by an absence of parasitic resistances and using the characteristic equation which corresponds to the equivalent electrical diagram, we determine the electrical parameters such as: the saturation current density (J₀), the short-circuit current density (J_sc), the open-circuit voltage (V_oc), the maximum power density point (J_m, V_m) and the fill factor (FF). The saturation current density is determined using fundamental semiconductor notions. The effect of the ideality factor on the electrical efficiency and the various parameters is also highlited. The results are applied to heterostructures based on CuInS₂ and CuInSe₂. The performance of the cell increases with a raising of the ideality factor (η) for the ideal solar cell model. By varying the ideality factor from 1 to 3, the calculated efficiency varies theoretically from 8.4% to 25.3% under AM1.5 solar spectrum for the structure based on CdS(n)/CuInS₂(p) named model (b) with a photocurrent density evaluated at 17 <i>mA.cm</i>^-2 by numerical calculation method. The efficiency varies from 6.8% to 20.45% for the structure based on CdS(n)/CuInSe₂(p) named model (a) with a photocurrent density evaluated at 31 <i>mA.cm</i>^-2 for the same used parameters. The open-circuit voltage varies from 0.5 V to 1.5 V for model (b) and from 0.27 V to 0.8 V for model (a). The results obtained (efficiency and electrical parameters) for each model remain within the range of experimental values published in the literature for solar cells based on chalcopyrite materials such as CIGS (CuIn_xGa_1-xSe₂ or CuIn_xGa_1-x(S_ySe_1-y)₂), and thus allowing to validate the different methods established to model the studied phenomena.