Composite materials of P3HT:PCBM with pyrene substituted zinc(II) phthalocyanines: Characterisation and application in organic solar cells

In the present work, novel composite thin films are investigated and applied as active layers in organic solar cells with improved performance. The novel composite materials are based on blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) with phenyl-C61-butyric acid methyl ester (PCBM) with the addition of symmetrically substituted zinc(II) phthalocyanine derivative bearing eight polyoxyethylene substituents (ZnPc-0py) or pyrene containing asymmetric zinc phthalocyanine (ZnPc-1py). The study of these novel composites in organic solar cells was carried out in two stages; firstly P3HT:ZnPc-0py and P3HT:ZnPc-1py were used as sensitizer layers between the active layer and PEDOT:PSS which has resulted in a declined power conversion efficiency compared to a P3HT:PCBM reference device. In the second stage ZnPc-0py and ZnPc-1py derivatives were used separately as a component in ternary blends within a mixture of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) (P3HT-PCBM in the ratio of 1:1) as an OSC active layer P3HT:PCBM. The photovoltaic characteristics of thin films of these blends have been investigated and optimum performance of ternary OSC devices has been identified. A ternary organic solar cell comprising P3HT:PCBM:ZnPc-1py as the active layer has demonstrated a power conversion efficiency as high as 2.96%, with fill factor of 57%, short circuit current density of 8.14 mAcm(-2) and open circuit voltage of 0.64 V.