Application of an Open-Circuit Voltage Decay Model to Compare the Performances of Donor Polymers in Bulk Heterojunction Solar Cells

We analyzed several polymeric solar cells fabricated by using four different donor polymers. On each device, we performed photocurrent, external quantum efficiency, and open-circuit voltage-decay transient measurements. A model was developed to explain the open-circuit voltage decay, which provided insight about the recombination mechanisms in the active layer and about the band diagram of the organic solar cell blend. By analyzing and comparing the data obtained with the open-circuit voltage-decay transient and the conventional dc measurements in the four polymers, the origin of lower performance in some devices was identified.