As we have seen majority carriers (electrons in n-type material holes in p-type) are the main players in a conventional semiconductor diode By initial diffusion across the p-n junction they set up a depletion layer and create a potential barrier Forward-biasing the diode reduces the height of the barrier marking it easier for them to cross the junction and produce substantial current in reverse bias the barrier increases and current flow is severely inhibited Diode action is principally due to the behaviour of majority carriers under the influence of an applied external voltage
With solar cells however it is light-generated minority carriers that take center stage the basic reason may be simply stated a potential barrier that inhibits transfer of majority carriers across a p-n junction positively encourages the transfer of minority carriers Whereas majority carriers
Experience a hill to climb minority carriers see a hill to roll down With luck they are swept down this hill collected at the cell terminals and produce an output current proportional to the intensity of the incident light