Results of light induced electron spin resonance (LESR) studies at 77 K on composites of new PPV-PPE copolymers with PCBM ([6,6]-phenyl-C₆₁-butanoic acid methyl ester) are presented. The aim is the comparison of their data with those of the state of the art material MDMO-PPV/PCBM to estimate their potential suitability for solar cell devices. The effective charge separation has been established by two LESR signals which were observed only under light excitation. They can be attributed to positive polarons (P⁺) on polymer chain with g = 2.0024 and to radical anions of PCBM molecule with g = 1.999. The dark signals were absent in all experiments for both types of radicals which clearly proves the fact of charge separation processes after light excitation in PPV-PPE/PCBM and PPVPPE/ PCBM blends. The 3-cm ESR techniques permits only an estimation, no really exact determination of relaxation parameters because of the strong linewidth anisotropy for different g–factors. Nevertheless T₁ and T₂ estimations and their relative order of magnitude were obtained analysing the saturation effect, which was noticed in all samples. This effect shows the dependence of LESR signal amplitude on microwave amplitude. Assuming a homogeneous broadening (or small inhomogeneous) of the individual PCBM radical signal the fitting was done using the function of the first derivative Y’ of a Lorentzian lineshape. The relaxation times T₁ and T₂ were determined from the saturation effect to be around 50 and 0.1 microsecond, respectively. The presented results show the very similar microscopic dynamic parameters of the new systems compared with the state of the art material (MDMO-PPV/ PCBM) which let us anticipate good perspectives concerning their suitability as possible solar cell components.