ESR spectroscopy of polarons in conjugated electroluminescent polymers

Polarons are non-linear excitations that carry spin and charge in conjugate d polymers. Spin distribution of polarons, or their spatial extension in ot her words, is one of the essential physical quantities that can be used to identify polarons. In this paper, we discuss the ESR and electron-nuclear d ouble-resonance (ENDOR) observation of polarons in an electroluminescent po lymer, poly(paraphenylene vinylene), PPV and its derivatives. Observed spin distribution extend over approximately four phenyl rings in half width, wi th its maximum density on the carbons of vinyl sites, and is well described by a theoretical calculation in the case of finite electron correlation. W e also discuss the light-induced ESR (LESR) observation of the excitation s pectra of photogenerated polarons, that compare well with those of photocur rents in PPV derivatives. (C) 2001 Elsevier Science B.V. All rights reserve d.