For the given circuit shown in figure, D1 is forward bias mode - On state D2 is in reverse bias mode - off state D3 is in reverse bias mode - off state.
For M no. of series configuration of solar cell, Open circuit voltage of PV module= M*Voc = 20*0.7 = 14 V Short circuit current of PV module = M*Isc = 20*4 = 80 A