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Solar, or photovoltaic (PV) cells produce electricity through a
variation of what is known as the photoelectric effect.
The effect describes the way that some surfaces (most commonly metal
surfaces) react to the presence of light by discharging electrons.
Initially it was believed that there was a direct relationship
between the strength of light that the surface came into contact with
and the force with which it would expel electrons.
However, the Hungarian experimentalist Philipp Eduard Anton von
Lenard discovered that this was not the case. His experiments showed
that it was the frequency, rather than the intensity, of the light which
dictated the strength with which the surface would emit electrons.
This finding created a paradox as it conflicted with the established
wave theory of light.
Einstein won 1921’s Nobel prize for his resolution of this problem –
he correctly suggested that a particular component within the light
(‘photons’) were responsible for causing the surface to emit electrons.
By increasing the frequency of the light rather than the intensity,
Einstein suggested, the surface could be made to discharge electrons
with greater force, thereby creating more electricity.
His theory proved correct.
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