Real Solar Cell and Determination Methods of Electrical Parameters

Abstract

In this work, we develop methods to determine the characteristic electrical parameters of a photovoltaic cell such as the photocurrent density (Jph), the saturation current density (J0), the short-circuit current density (Jsc), the open-circuit voltage (Voc), the maximum power density point (Jm , Vm), the fill factor (FF) and the electrical conversion efficiency (etaC) according to the irradiance spectrum. The real solar cell model is considered for the determination of these various parameters. This model takes into account the effect of shunt and series resistances (parasitic resistances). Notions of semiconductor physics, continuity equation of charge carriers combined to optoelectronic and geometrical properties of the materials, numerical resolution method to solve implicit equations based on characteristic equation of a photodiode, are notions mainly exploited to determine electrical parameters of the real solar cell. The results are applied to the heterostructures ZnO(n+)/CdS(n)/CuInS2(p)/ CuInSe2(p+) named CIS and ZnO(n+)/CdS(n)/CuInSe2(p)/CuInS2(p+) named CISE to evaluate their performances according to the considered parameters. The results obtained for each structure, photocurrent density ~ 17 mA.cm-2 (CIS) and 31 mA.cm-2 (CISE), short-circuit current density ~ 16.79 - 17 mA.cm-2 (CIS) and 30.62 - 31 mA.cm-2 (CISE), open-circuit voltage ~ 0.76 V (CIS) and 0.52 V (CISE), fill factor ~ 0.648 - 0.745 (CIS) and 0.545 - 0.677 (CISE), maximum power density ~ 8.28 - 9.69 mW.cm-2 (CIS) and 8.72 - 11.02 mW.cm-2 (CISE), saturation current ~ 4.117×10-8 mA.cm-2 (CIS) and 1.169×10-3 mA.cm-2 (CISE), are in the same magnitude order as the values published in the literature. We obtain under AM 1.5 solar spectrum and taken into account the parasitic resistances, a theoretical conversion efficiency ranging from 9.93% to 11.62% for the model CIS and from 10.46% to 13.22% for the model CISE. Thus, these results allow to validate the various models established to model the phenomena studied.