Photoexcitations in carbazolyl substituted polydiacetylene (PDA) fullerene composites

It is well known that many non-degenerate ground state conjugated polymers like PPV derivatives show an ultrafast electron transfer to fullerenes upon photoexcitation. In this work we investigate the photoexcited states of fullerene — carbazolyl substituted PDA composites and compare them to the pristine components. We report the finding of photoexcited spins as well as charges in one asymmetric carbazolyl substituted PDA, the CPDO (poly(1-N-carbazolyl-penta-1,3-diyne-5-ol)). While PIA FTIR measurements show strong IRAV bands for this material, LESR studies on the same samples reveal photoexcited spins. Although CPDO samples show a dark ESR signal, which is well known for the topochemical polymerization, photoexcitation studies clearly reveal, that the LESR does not come from photoinduced polymerization. No enhancement of LESR signal is found for mixtures of CPDO and fullerenes, in our case a special solubilized fullerene, PCBM. We conclude therefore, that even PDA which show photoexcited charges and spins, do not exhibit a photoexcited charge transfer to fullerenes.