Its not normal practise to use a Solar panel by itself to power electronics.
You usually need a battery which the Solar panel charges, and the battery provides the power to run the
electronics.
As other posters have indicated, solar panels are current sources and the current produced is proportional to the
light falling on the panel.
The best arrangement is Solar Panel > MPPT charger > battery > electronics to be powered.
You can also use Solar Panel > PWM charger > battery > electronics to be powered, but this loses around 30%
of the Solar panels capacity.