Spin distributions and excitation spectra of optically generated polarons in poly(phenylenevinylene) derivatives

Light-induced electron spin resonance (LESR) measurements have been perform ed on two dialkoxy derivatives (MEH-PPV and CN-PPV) of poly(p-phenyleneviny lene) where cyano groups are attached at the vinylic carbon sites in CN-PPV , The transient response and excitation spectra of the LESR signals indicat e that the observed spins are optically generated polarons, A clear reducti on of ESR linewidth has been observed in CN-PPV compared with MEH-PPV, prov iding direct evidence that the polaron spin density resides predominantly o n the vinylic carbons. Linewidth analysis based on a theoretical model for the spin distribution yields an extension of the polaron over approximately four phenyl rings. (C) 2000 Elsevier Science B.V. All rights reserved.