Figure 3. J–V characteristics.

(a) Linear–linear (top) and log-linear (bottom) J–V characteristics of an optimized ultrathin OPV device on 1.4 μm PET substrate. The device performance metrics are V_OC=580 mV, J_SC=11.9 mA cm⁻², FF=61% and η=4.2%. Solid lines are measured under one sun illumination and dashed lines in the dark (also in b,c). (b) Device performance of reference device, using the same materials but constructed directly on glass substrates without PET. The device performance metrics are V_OC=565 mV, J_SC=11.9 mA cm⁻², FF=61% and η=4.1%. Comparing the J–V curves of a and b, nearly identical behaviour is observed. The V_OC of this particular device is slightly lower, but overall the performance of the glass and PET-based solar cells is indistinguishable. (c) Ultrathin OPV devices on PET foil with underlying silver grid can attain FF up to 71% (top) and dark diode rectification of up to 6 orders of magnitude at ±1 V (bottom). However, they typically show lower J_SC due to shading from the silver grid.