Two 1n4007 is fine considering the ease of making and the solar panel being 9 v or 12 v plenty of voltage available for the 2 v drop.
Solar panel circuit board.
For night time switching you may have to use a delay on timer with the circuit.
In this circuit the solar panel charges up a 3 cell nimh battery 3 6 v.
1 x 1 2 volt battery at least 1 5 volt solar cell in full sun.
The top countries of suppliers are china taiwan china and hong kong s a r from which the percentage of solar circuit board supply is 98 1 and 1 respectively.
It offers the advantages of low power dissipation low minimum operating voltage and automatic dusk to dawn switching.
So batteries and the circuit dictate the solar cell size there are some of these lights with pr sensors that use a 3 7 volt battery and a solar cell of 4 5 volts.
The lights won t turn on until the solar panel voltage became 1 v or lower that will happen at extreme dusk but not at night.
It requires only an external inductor to construct a boost power supply with over 90 per cent efficiency.
2 x 1 2 volt batteries at least 3 volt solar cell in full sun.
1 x 3 7 volt battery at least 4 5 volt solar cell in.