Fill Factor (FF) [%]
Relationship between the maximum power and the product resulting from the open circuit voltage by the short-circuit current of a PV device. This factor shows how much the pattern of the device I-V curve is near to the ideal rectangular shape.
Secondary connection, usually of silver, connected to the busbar and applied on the cell side exposed to light.
Fixed tilt array
PV array whose module supporting structure has a fixed tilt.
The number of repetitions per unit time of a complete waveform, expressed in Hertz (Hz).
A device that converts the energy of a fuel directly to electricity and heat, without combustion. Because there is no combustion, fuel cells give off few emissions; because there are no moving parts, fuel cells are quiet.