Fullerene Blend Films Research Articles

Mixed Solvents for Morphology Control of Organic Solar Cell Blend Films

Poly(3-hexylthiophene) (P3HT) and fullerene derivative blend films formed by spin-coating from mixtures of ethanol and chloroform as solvent were studied. Compared with the blend films made from chloroform alone, films made with increasing ethanol concentration in the solvent showed greater degrees of P3HT crystallinity and increased phase segregation of the polymer and fullerene as observed by changes to the absorption spectra, photoluminescence spectra and optical microscope pictures.

Photoemission investigation on copper phthalocyanine:fullerene blend film

The electronic structure of thin blend films composed by copper phthalocyanine (CuPc) and fullerene (C60) have been studied by soft x-ray photoemission spectroscopy. Several samples with different C60∕CuPc concentration ratios were prepared by thermal evaporation in ultrahigh vacuum conditions. As the C60 concentration increases, strong shifts of the CuPc highest occupied molecular orbital (HOMO) level towards the Fermi level and of the C60 HOMO level to higher binding energies have been observed. This experimental result suggests that there is a sizeable interaction between CuPc and C60 molecules that can be interpreted in terms of a charge transfer from C60 to CuPc. These shifts play an important role in the application of the CuPc:C60 blend films for instance in the construction of solar cells on flexible substrates.

Radical ion pair mediated triplet formation in polymer–fullerene blend films

Efficient triplet formation is observed for films of high ionisation potential polythiophenes blended with a fullerene derivative, and assigned to formation via geminate charge recombination of bound radical ion pair states.

Stabilization of the nanomorphology of polymer–fullerene “bulk heterojunction” blends using a novel polymerizable fullerene derivative

The morphological stabilization of donor–acceptor blends for bulk heterojunction solar cells can be achieved by cross-linking of the small molecular phase in the polymer matrix using a polymerizable fullerene derivative. In a comparative study the morphology of polymer–fullerene blend films was investigated using poly(3-hexylthiophene) (P3HT) as the polymer and C61-butyric acid methyl ester (PCBM) or the newly synthesized polymerizable fullerene derivative, C61-butyric acid glycidol ester, PCBG, as the acceptor molecule, respectively. Changes in the nanomorphology due to heat treatment of the films were studied by means of atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL) studies. The polymerization process was monitored with infrared absorption studies. As demonstrated by these comparative studies this newly synthesized fullerene gives considerable stabilization of the solid state morphology in these blends. Such prevention of the long term, high temperature instability of bulk heterojunction morphology displays an important route to increase the operational stability of plastic solar cells in future applications.