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The open-circuit saturation curve (also open-circuit characteristic, OCC) of a synchronous generator is a plot of the output open circuit voltage as a function of the excitation current or field. The curve is typically plotted alongside the synchronous impedance curve .
When the cell is operated at open circuit, = 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 OC is:
where is the breakdown voltage in volts, is the pressure in pascals, is the gap distance in meters, is the secondary-electron-emission coefficient (the number of secondary electrons produced per incident positive ion), is the saturation ionization in the gas at a particular / (electric field/pressure), and is related to the excitation and ...
The voltage v oc between the terminals is the open-circuit voltage of the device. Black curve: The highest possible open-circuit voltage of a solar cell in the Shockley-Queisser model under unconcentrated sunlight, as a function of the semiconductor bandgap. The red dotted line shows that this voltage is always smaller than the bandgap voltage.
Shockley derives an equation for the voltage across a p-n junction in a long article published in 1949. [2] Later he gives a corresponding equation for current as a function of voltage under additional assumptions, which is the equation we call the Shockley ideal diode equation. [3]
For a circuit using a battery source, the emf is due solely to the chemical forces in the battery. For a circuit using an electric generator, the emf is due solely to a time-varying magnetic forces within the generator. Both a 1 volt emf and a 1 volt potential difference correspond to 1 joule per coulomb of charge.
The curve is typically plotted alongside the open-circuit saturation curve. [1] The SCC is almost linear, since under the short-circuit conditions the magnetic flux in the generator is below the iron saturation levels and thus the reluctance is almost entirely defined by the fixed one of the air gap.
One device used polyacetylene (Fig. 1) as the organic layer, with Al and graphite, producing an open-circuit voltage of 0.3 V and a charge collection efficiency of 0.3%. [21] An Al/poly(3-nethyl-thiophene)/Pt cell had an external quantum yield of 0.17%, an open-circuit voltage of 0.4 V and a fill factor of 0.3. [ 22 ]