The spin signature of charged photoexcitations in carbazolyl substituted polydiacetylene

Abstract

Zero-field electron spin resonance and theoretical studies of light penetration into single crystal and polycrystalline material doped with molecules photoexcitable to the triplet state via intersystem crossing In this article, photoinduced infrared absorption ͑PIA-FTIR͒ and light induced electron spin resonance ͑LESR͒ measurements on an asymmetric carbazolyl substituted polydiacetylene ͑PDA͒, the poly͕1-͑N-carbazolyl͒ penta-1,3-diyn-5-ol͖ ͑polyCPDO͒ are presented. Results from both experimental techniques imply that contrary to other well-known polydiacetylene derivatives, in polyCPDO there exist only long-living, highly localized charged photoexcitations with spin 1/2 ͑g valueϳ2.0026͒, indicative for polaronic excitations. PolyCPDO also shows a strong dark ESR signal with the same g value as the LESR signal and with a Curie susceptibility of approximately 10 Ϫ3 spins per CPDO monomer unit. This unusually high number of defects may come from intermediates of the polymerization. Furthermore, the photoexcited states of composites from polyCPDO mixed with a special solubilized methano-fullerene ͓6,6͔-Phenyl C 61 -butyric acid methyl ester ͑PCBM͒ with excellent acceptor properties are investigated and compared with those of the pristine polymer. No enhancement of PIA-FTIR and LESR signals is found for these composites. It is therefore concluded, that even polyCPDO, which shows charged spin 1/2 photoexcitations, does not exhibit a photoexcited charge transfer to fullerenes as observed in other nondegenerate ground state conjugated polymer fullerene composites.

Optical Projection and Spatial Separation of Spin-Entangled Triplet Pairs from the S1 (21 Ag–) State of Pi-Conjugated Systems

“…One final possible consideration is that the push activates dark, intermediate charge-transfer or polaron states. In measurements of C 60 doped and carbazolyl modified PDAs, 84,85 no intermolecular charge-transfer bands were observed, suggesting CT exciton formation to be unfavorable. This may also explain why primarily only the triplet-pair amplitudes in the 2 1 A g wavefunction appear to be addressed by the push.…”

Influence of molecular designs on polaronic and vibrational transitions in a conjugated push-pull copolymer

“…Taking PBDTTT-c as an example, little is know about the influence of such complexity to the polaron levels. Therefore we pursue an operando spectroscopic study to achieve this insight, in particular on polaron dynamics 24 25 26 27 28 29 30 .…”

Fullerene-modified polyamide 6 by in situ anionic polymerization in the presence of PCBM

“…Buckminsterfullerene C 60 and its functionalized derivatives have attracted considerable attention due to their large number of potential applications in organic photovoltaics [1], organic field effect transistors [2], quantum information processing [3], as antioxidants and biopharmaceuticals [4], and in water purification systems [5]. Polymer composites suitable for preparation of electronic and optical materials with appropriate photoinduced electron transfer or photoexcitation properties may be based on conjugated polymer matrices modified by fullerene compounds [6,7]. Conventional polymers such as polyethylene [8,9] and polystyrene [10][11][12][13] have also been tested as matrices for fullerenes.…”