Photo-induced charge separation process in (PCBM-C120O)/(M3EH-PPV) blend solid film studied by means of X and K-bands ESR at 77 and 120 K

The new fullerene dimer adduct PCBM-C120O was studied as an electron acceptor by light-induced ESR (LESR) when blended with the electron donor-conjugated polymer M3EH-PPV in a thin solid film. ESR parameters for the PCBM-C120O anion radical and the M3EH-PPV polaron (triaxial gx,y,z factors) were determined by X- and K-band ESR techniques at temperatures of 77 and 120 K. It was found that isotropic g0 of PCBM-C120O anion radical ESR spectra obtained in this blend under illumination is close to g-factors of electrochemically reduced (C120-O)− and does not coincide with the analogous parameter of (C120-O)2− (reported in literature). Spin relaxation parameters (T1 and T2) of the PCBM-C120O anion radical and M3EH-PPV positive polaron are similar to T1, T2 for light-induced ion radicals in the P3HT/PCBM blend.