Current-voltage output characteristic solar-cell

The photogenerated current is in the same direction as /, but is always less than because the battier potential under load conditions is always less than F, which results in a larger flow of majority carriers than that in a short-circuited cell. Thus, when a solar cell is under load, the current and voltage are always less than and lU, respectively this condition is the curve-factor loss. Depending on the characteristics of the particularp—n junction and on the cell operating conditions, there is an optimal load resistance that maximizes the power output of the cell, ie, the product of its current and voltage. 

Fig. 5.21. Top figure The experimental plots of dark and illuminated J—V characteristics of a typical MDMO-PPV/PCBM solar cell for different concentrations of PCBM. The currents are plotted on the log scale. Curves 1 are for dark currents and curves 2 are for illuminated currents. The open circles show the dark currents needed to make the output current zero at the open circuit voltage. Bottom figure The current densities are plotted on the linear scale for two PCBM concentrations. Curves 1 are for dark currents and curves 2 are for illuminated currents.

Fig. 1 Matching of current-voltage characteristics of solar cell and electrolyzer (a) at constant light power density 1, 2, 3 - characteristics of solar cell at Ng = 1,2, and 4 (at Sj = const) 4 - characteristic of electrolyzer (Ng = 1) o - maximum power point (MPP) dashed line shows the locus of maximum cell output power at the given radiation power density (b) at varying radiation power density 1 , 2, 3, -characteristics of solar cell dashed line - locus of MPP hatched area - variations of MPP in the most probable limits of variation of the light power density and temperature 4 - characteristic of electrolyzer.

Principles of simulation have been elaborated by Carpetis [22] who introduced the current-voltage characteristic of the solar cell in an implicit form, O (I, Vj, T, J) = 0 where Ig and Vg are the cell output photocurrent and voltage respectively, T is the cell temperature, and J is the solar radiation intensity. Besides four variables the function O contains also five constants which are to be determined from five independent sets of experiments. 

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