We revisit the argument that link the efficiency of a solar cell to its reverse operation as a LED, in the case where the material is organic. In organic cells, exciton transport is an intermediate process between sunlight absorption and the generation of electric current. We show that quenching exciton radiation can be beneficial to cell efficiency, without contradicting the general rule prevailing for semiconductor cells. Our treatment allows us to discuss both bulk heterojunction and planar junctions.