Photophysics of pristine and C60-doped disubstituted polyacetylene

Using a variety of steady-state spectroscopies we studied the long-lived photoexcitations and electronic excited states of poly disubstituted acetylene (PDPA-nBu), the backbone structure of which is a disubstituted trans-polyacetylene, as well as PDPA-nBu/C60 blends. The cw spectroscopies include absorption, photoluminescence (PL), photoinduced absorption (PA), and PA-detected magnetic resonance (PADMR). Although Using a variety of steady-state spectroscopies we studied the long-lived photoexcitations and electronic excited states of poly disubstituted acetylene (PDPA-nBu), the backbone structure of which is a disubstituted trans-polyacetylene, as well as PDPA-nBu/C60 blends. The cw spectroscopies include absorption, photoluminescence (PL), photoinduced absorption ~PA!, and PA-detected magnetic resonance (PADMR). Although PDPA-nBu is a degenerate ground-state polymer, nevertheless, and in contrast to trans-polyacetylene, we found that it has a strong PL band with quantum efficiency larger than 60%. From polarized PL studies on stretched oriented films we conclude that the PL emission originates from intrachain excitons rather than the polymer side groups. This shows that the lowest-lying exciton in PDPA-nBu is a Bu state rather than an Ag state, in contrast to the order of the lowest-lying excitonic states in trans-polyacetylene. The polarized absorption in PDPA-nBu contains three distinctly different bands with different polarization properties, which are interpreted according to the model of Shukla and Mazumdar.