Light-soaking effects on ZnO-nanorods/polymer hybrid photovoltaics

The solar cell properties of polymer/ZnO-nanorods hybrid photovoltaics were improved by UV irradiation. However, the effects of UV irradiation were different from those reported for polymer photovoltaics made of a bulk heterojunction and a metal-oxide interlayer. In the case of the hybrid photovoltaics, in contrast to the devices with a bulk heterojunction, no inflection points were observed in the photocurrent-voltage curves of fresh devices, and an additional component of the photocurrent was induced by UV irradiation, leading to an increase in the photocurrent. The appearance of the second component of photocurrent was attributed to removal of oxygen, which impedes splitting of excitons into carriers, from the surface of ZnO nanorods by UV irradiation. Removal of oxygen was accelerated by the presence of a small amount of organic materials because oxygen was consumed while organic materials were photocatalytically decomposed by UV irradiation.