Factors Affecting the Performance of Bifacial Inverted Polymer Solar Cells with a Thick Photoactive Layer

Abstract

Photocurrent voltage curves and photocurrent action spectra of bifacial inverted polymer solar cells with a structure of ITO/ZnO/[6,6]-phenyl C61 butyric acid methyl ester (PCBM):regioregular poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid) (PEDOT:PSS)/Au were measured. High performance was obtained when light was irradiated from each side of the devices, even for those with a 500 nm thick PCBM:P3HT layer, but an optical filter effect of the photocurrent was somewhat larger for irradiation from the Au side than that for the ITO side. These results suggested that the efficiency of photocharge separation near the ZnO/PCBM:P3HT interface was higher than that near the PCBM:P3HT/PEDOT:PSS interface, although the photocharge separation and the charge transport were smooth in the whole PCBM:P3HT layer. Further, we found that the fill factor of the photocurrent voltage curves of these devices depended on the migration distance of holes with lower mobility in the PCB...