Definition of open-circuit voltage. The box is any two-terminal device, such as a battery or solar cell. The two terminals are not connected to anything (an "open circuit"), so no current can flow into or out of either terminal. The voltage voc
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.
Open-circuit voltage (abbreviated as OCV or VOC ) is the difference of electrical potential between two terminals of a device when disconnected from any circuit. There is no external load connected. No external electric current flows between the terminals. It is sometimes given the symbol Voc. In network analysis this voltage is also known as the Thévenin voltage.
The open-circuit voltages of batteries and solar cells are often quoted under particular conditions (state-of-charge, illumination, temperature, etc.).