Fill factor

Fill factor in the context of solar cell technology is defined as the ratio (given as percent) of the actual maximum obtainable power, (V_mp x J_mp) to the theoretical (not actually obtainable) power, (J_sc x V_oc).

This is a key parameter in evaluating the performance of solar cells. Typical commercial solar cells have a fill factor > 0.70. Grade B cells, have a fill factor usually between 0.4 to 0.7.

The fill factor (FF), is thus defined as (V_mpJ_mp)/(V_ocJ_sc), where J_mp and V_mp represent the current density and voltage at the maximum power point, this point being obtained by varying the resistance in the circuit until J x V is at its greatest value.

The Fraunhofer ISE has showed an organic photovoltaic cell featuring a record fill factor of 64 %.

Other uses

Other uses of the term:

• In vision science, the fill factor is the ratio of view areas to the object visible areas.
• For optical micro-lens arrays, the fill factor is defined as the ratio of the active refracting area to the total contiguous area occupied by the lens array.

References and further reading

General references

• "T.Bazouni: What is the Fill Factor of a Solar Panel". Retrieved 2009-02-17.