Density functional theory study on the interaction of C₆₀ fullerene with PCBM

Functionalized fullerenes are known as high-performance molecules. Herein, the interaction of C-60 fullerene with Phenyl-C-61-butyric-acid-methyl-ester (PCBM) is investigated by means of density functional theory method to elucidate the structures and electronic states of C-60-PCMB complexes. C-60-PCBM blends are typically used in solar cell. Studying the electronic structure of C-60-PCBM is important for elucidating the mechanism of solar cells. The intermolecular distances for C-60 and PCBM dimers were calculated to be 3.70 and 2.34 & Aring;, respectively. In C-60 dimer, the five membered ring of C-60 interacted with the six membered ring of neighbour C-60. Two hydrogen bonds between side chains of PCBM are connected in the PCBM dimer. The binding energies were 1.4 kcal mol(-1) (C-60 dimer) and 2.6 kcal mol(-1) (PCBM dimer). In the C-60-PCBM complex, five different structures were found to be stable. The binding energies were distributed in the range 1.6-3.7 kcal mol(-1). The electronic states and excitation energies of C-60-PCBM complexes and the basis set superposition error were discussed on theoretical results.