i = 0 is open circuit voltage in a solar cell.
i = 0 is open circuit voltage in a solar cell.
what is open circuit voltage in a solar cell?
i = 0
the general form of the solution is a curve with "i" decreasing as "v" increases (see graphs lower down). the slope at small or negative "v" (where the "w" function is near zero) approaches formula_13, whereas the slope at high "v" approaches formula_14.









































section::::equivalent circuit of a solar cell.:characteristic equation.:open-circuit voltage and short-circuit current.









































when the cell is operated at open circuit, "i = 0" and the voltage across the output terminals is defined as the "open-circuit voltage". assuming the shunt resistance is high enough to neglect the final term of the characteristic equation, the open-circuit voltage "v" is:
theory of solar cells
the open-circuit voltage formula_22 of a solar cell is the voltage created by a certain amount of illumination if the contacts of the solar cell are not connected, i.e. in open circuit. the voltage that can build up in such as situation is directly connected to the density of electrons and holes in the device. these densities in turn depend on the rates of photogeneration (determined by the amount of illumination) and the rates of recombination. the rate of photogeneration is usually determined by the typically used illumination with white light with a power density of 100mw/cm (called one sun) and by the band gap of the solar cell and does not change much between different devices of the same type. the rate of recombination however might vary over orders of magnitude depending on the quality of the material and the interfaces. thus, the open-circuit voltage depends quite drastically on the rates of recombination at a given concentration of charge carriers. the highest possible open-circuit voltage, the radiative open-circuit voltage formula_23, is obtained if all recombination is radiative and non-radiative recombination is negligible. this is the ideal situation, because radiative recombination cannot be avoided other than by avoiding light absorption (principle of detailed balance). however, since absorption is a key requirement for a solar cell and necessary to achieve a high concentration of electrons and holes as well, radiative recombination is a necessity (see van roosbroeck-shockley equation ). if non-radiative recombination is substantial and non negligible, the open-circuit voltage will be reduced depending on the ratio between the radiative and non-radiative recombination currents (where the recombination currents are the integral of the recombination rates over volume). this leads to a second reciprocity relation between the photovoltaic and the luminescent operation mode of a solar cell because the ratio of radiative to total (radiative and non-radiative) recombination currents is the external luminescence quantum efficiency formula_24 of a (light emitting) diode. mathematically, this relation is expressed as,
reciprocity (optoelectronic)