What is the efficiency of a photovoltaic cell?

Explication

Efficiency compares what the cell delivers electrically with the light falling on it, and strictly it is a ratio of powers — electrical output P = V × I divided by incident optical power — so the keyed wording “converted to current” is imprecise, because current alone is not a power. It remains the best of the four, since output-over-input RF power and lumens per watt describe amplifiers and lamps, and open-circuit voltage divided by short-circuit current is a resistance rather than an efficiency.