Hello
when connect solar panel in parallel they should be a bypass diode put in the circuit.
So the question is when connect solar panel in series if put bypass diode in the circuit would the solar panel work just as good with bypass diode in circuit or been that this is a series circuit put diode in the circuit would make solar panel produces less volts.
Mrel

 

If the diode is in series with the panel, then the voltage will drop by the junction of the diode. About 3/4 volt with a silicon diode or 1/3 volt with a Schottky diode.

 

You only need bypass diodes when panels are connected in series. Bypass diodes are connected in parallel with the panel. If the panel get shaded, they provide a path for current from other panels to bypass the shaded panel.

You do not need bypass diodes when panels are connected in parallel.

Bypass diodes are often installed in the panel junction box, so you don't need external ones.