UV-excited ESR (UV-ESR) and optically detected magnetic resonance (UV-ODMR) studies of /spl pi/-conjugated polymers

Summary form only given. The UV-ODMR of poly(p-phenylenevinylenes) (PPVs), poly(p-phenylene-acetylenes) (PPAs), poly(3-alkylthiophenes) (P3ATs), and poly(p-diphenylene-aniline-acetylene) (PDPAA) derivatives is described and compared to the ODMR observed by visible excitation. Visible excitation of PPVs, PPAs, and P3ATs yields a narrow photolurninescence (PL)-enhancing polaron resonance and full- and half-field PL-enhancing triplet exciton resonances. However, excitation of PPVs at /spl lambda//sub ex//spl les/ 353 nm and P3ATs at /spl lambda//sub ex//spl les/ 308 nm weakens the PL intensity and yields an intense narrow PL-quenching resonance which is observed in addition to the polaron resonance. In the relatively highly disordered PPAs and the higher-gap PDPAAs no such quenching resonance is observed. It is tentatively suggested that the polaron levels are stabilized by defects, the fundamental absorption edge is due to a rigid singlet exciton, and that the narrow PL-quenching ODMR is due to the dynamics of electrons and holes in the continuum bands.