Long-lived photoexcited states in polydiacetylenes: The photoinduced-absorption spectra of PDA-4BCMU

Comoretto, Davide; Moggio, Ivana; Cuniberti, C.; Musso, G. F.; Dellepiane, G.; Borghesi, A.; Kajzar, F.; Lorin, André

doi:10.1103/physrevb.57.7071

Cited by 18 publications

(17 citation statements)

References 64 publications

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“…Since in our experiments we cannot monitor the transient change of the ground state, we prefer to interpret our data in the framework of the trap density which has been successfully used in the past. 6,53 The estimated value of g for polyDCHD-HS in the s time regime is about 0.5 ͑see Table I͒, similar to the values obtained for other conjugated polymers, 56,68 and much higher then those obtained for highly luminescent polymers. 69 This value of g for triplet excitons indicates that half of the photoexcitation density follows different decay pathways.…”

Section: Resultssupporting

confidence: 80%

“…For several years our group has been interested in the preparation of diacetylenic monomers, their polymerization, 1,2 the study of their photophysical, [3][4][5][6][7] and electronic properties 8,9 as well as in the evaluation of their non linear optical ͑NLO͒ properties, [10][11][12] which are potentially suitable for photonic applications. 13 The nonlinear optical properties of these materials depend on the nature of the electronic excited states.…”

Section: Introductionmentioning

confidence: 99%

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Triplet excitons in acyl- and alkyl-substituted polycarbazolyldiacetylenes: A spectroscopical and photophysical study

et al. 2004

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Absorption, photoluminescence, and photoinduced absorption ͑PIA͒ spectra of films of red phase polycarbazolyldiacetylenes ͑polyCzDAs͒ carrying selected acyl ͑polyDPCHD͒ or alkyl ͑polyDCHD-HS͒ groups are reported. The absorption spectrum of polyDCHD-HS, which is almost independent of the temperature down to 20 K, shows an excitonic absorption followed by an inhomogeneously broadened vibronic progression. Very different is instead the case of polyDPCHD whose thin films show a very sharp excitonic transition and a vibronic progression with a lower electron-phonon ͑el-ph͒ coupling with respect to that of polyDCHD-HS. These peculiar characteristics allow the detection of additional features in the spectra, which are assigned on the basis of quantum chemical calculations to string modes of the backbone. As far as thick films of polyD-PCHD are concerned, broad electronic spectra are observed. Raman spectroscopy studies suggest that this broadening is due to the presence of two forms of the polymer. Unlike other polydiacetylenes ͑PDA's͒ including polyDCHD-HS films, polyDPCHD films are also strongly luminescent, thus suggesting a different ordering of the dipole forbidden and allowed states. For these materials, the photoinduced absorption spectra are dominated by triplet excitons. Effects of different forms in acyl substituted polymers are observed also in the PIA spectra. The rise and decay of the triplet signal for polyDCHD-HS are accounted for through a dynamical model, which includes saturation effects in the monomolecular decay regime. A more complex kinetics is instead observed for polyDPCHD. From the study of the kinetics of the PIA spectra both the triplet generation efficiency and the density of traps are evaluated.

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Section: Resultssupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Triplet excitons in acyl- and alkyl-substituted polycarbazolyldiacetylenes: A spectroscopical and photophysical study

et al. 2004

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“…The influence of the charge localization on the D and A blocks can promote intra-molecular charge separation, which could benefit charge generation in organic solar cells [20,33,34]. Chemical doping [33,35], electrochemical doping [36], and photoinduced absorption [37] have all proven useful in the investigation and characterization of the nature of charged species and photoexcited states in organic semiconductors. In this work we present results of chemical doping, electrochemical doping and photoinduced absorption studies on PDPP-FPF, PDPP-FNF, PDPP-FAF, and PDPP-TNT.…”

Section: Introductionmentioning

confidence: 99%

Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

et al. 2014

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A strategy that is often used for designing low band gap polymers involves the incorporation of electron-rich (donor) and electron-deficient (acceptor) conjugated segments within the polymer backbone. In this paper we investigate such a series of Diketopyrrolopyrrole (DPP)-based co-polymers. The co-polymers consisted of a DPP unit attached to a phenylene, naphthalene, or anthracene unit. Additionally, polymers utilizing either the thiophene-flanked DPP or the furan-flanked DPP units paired with the naphthalene comonomer were compared. As these polymers have been used as donor materials and subsequent hole transporting materials in organic solar cells, we are specifically interested in characterizing the optical absorption of the hole polaron of these DPP based copolymers. We employ chemical doping, electrochemical doping, and photoinduced OPEN ACCESSPolymers 2015, 7 70 absorption (PIA) studies to probe the hole polaron absorption spectra. While some donor-acceptor polymers have shown an appreciable capacity to generate free charge carriers upon photoexcitation, no polaron signal was observed in the PIA spectrum of the polymers in this study. The relations between molecular structure and optical properties are discussed.

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“…3 This picture has been questioned in the last few years by systematic cw-PIA and PIA-FTIR studies on several PDAs and in particular on carbazolyl substituted PDAs ͑PCzDAs͒. [4][5][6][7][8][9][10][11][12][13] Especially PCzDAs are an interesting model system for the photoexcitation processes in PDAs, as they show photoexcited charged states. The photoexcitation scheme for long-lived charged states in PCzDAs can be summarized in the following way.…”

Section: Introductionmentioning

confidence: 99%

The spin signature of charged photoexcitations in carbazolyl substituted polydiacetylene

Brabec

Johansson

Cravino

et al. 1999

The Journal of Chemical Physics

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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.

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Long-lived photoexcited states in polydiacetylenes: The photoinduced-absorption spectra of PDA-4BCMU

Cited by 18 publications

References 64 publications

Triplet excitons in acyl- and alkyl-substituted polycarbazolyldiacetylenes: A spectroscopical and photophysical study

Triplet excitons in acyl- and alkyl-substituted polycarbazolyldiacetylenes: A spectroscopical and photophysical study

Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

The spin signature of charged photoexcitations in carbazolyl substituted polydiacetylene

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