Anisotropic Polaron Motion in Polyaniline Studied by Muon Spin Relaxation

Pratt, F. L.; Blundell, Stephen J.; Hayes, W.; Nagamine, K.; Ishida, K.; Monkman, Andrew P.

doi:10.1103/physrevlett.79.2855

Cited by 75 publications

(55 citation statements)

References 22 publications

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“…1) suggests that the sites marked I and II, and corresponding similar sites in the same and other aromatic rings, are good candidates for the muon localization, assuming that muonium adds to unsaturated bonds as for other muoniated radicals [5,6]. The hyperfine interactions for addition at similar sites might be indistinguishable within the experimental resolution, resulting in only two measured values.…”

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confidence: 99%

“…They indicate the onset of a small relaxation at about 250 K. The presence of a dynamical spin relaxation rate provides information on the electronic interaction with charge carriers in the LUMO band. Although Zn-Pc has a non-polymeric structure, inter-and intra-molecular charge carrier diffusion may occur in analogy to the related polymer chain behaviour [5,6]. Since intermolecular diffusion directly affects the semi-conducting behaviour of these materials, its characterization is an obvious objective to pursue.…”

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confidence: 99%

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Muoniated radicals in the organic semiconductor zinc-phthalocyanine

Duarte

Vilão

Gil

et al. 2003

Physica B: Condensed Matter

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mSR experiments were conducted on the organic semiconductor zinc-phthalocyanine (Zn-Pc) in order to identify and characterize the muon states in this material. Transverse-field experiments at 0.5 mT reveal the existence of paramagnetic muon states in Zn-Pc, with the formation probability of nearly 100%. Two different muoniated radicals were detected, with hyperfine parameters of 127 and 142 MHz; muonium is thus bound to the Zn-Pc molecule at two different sites. Preliminary longitudinal field measurements indicate the onset of spin dynamics above 200 K. The observed relaxation is interpreted as due to spin exchange scattering with charge carriers. The utilization of organic materials is becoming increasingly important in general electronics, ranging from organic displays to solar cells. These materials offer many unique features (such as the possibility of having electronic components assembled in flexible plastic substrates). In addition, manufacturing devices made up of such compounds imply in principle low-cost production processes and the respective raw materials are abundant and readily available [1].It is well known that doping is a major tool for the enhancement of semiconductor-based devices. Although organic semiconductors have long been studied per se [1], almost nothing is known about the effect of doping on their electronic properties. While organic semiconductors have many electronic properties akin to the properties of inorganic ones, they must behave, as regards doping, in a manner comparable to the latter (in the silicon industry, for instance, hydrogen is known to play an important role in the manufacturing and efficiency enhancement of solar cells).mSR is a particularly valuable tool to assess the influence of doping in these materials, the muonium acting either as a substitute for isolated hydrogen in the material or as a probe for effects due to other dopant atoms or molecules. Moreover, being a local probe technique, mSR provides detailed information about electronic properties at a microscopic level.

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confidence: 99%

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confidence: 99%

Muoniated radicals in the organic semiconductor zinc-phthalocyanine

Duarte

Vilão

Gil

et al. 2003

Physica B: Condensed Matter

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“…10,11 It is generally assumed that the positive muon captures one electron upon stopping, forming a neutral system known as muonium ͑Mu͒. Muonium adds to unsaturated molecules by breaking double bonds, forming muoniated radicals.…”

Section: Introductionmentioning

confidence: 99%

Muoniated radical states in the organic semiconductor phthalocyanine

et al. 2006

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Phthalocyanine samples of ZnPc, H 2 Pc, and CuPc were investigated with the muon spin rotation technique. In ZnPc and H 2 Pc, three muoniated radical states of paramagnetic origin were identified, two of which have hyperfine interactions in the range 110-150 MHz and correspond to muonium addition at the outer benzene rings. The third state has a smaller hyperfine interaction ͑about 25 MHz͒ and is tentatively assigned to addition at bridging nitrogen atoms. CuPc has an unpaired electron from the Cu atom, which originates a diamagneticlike signal upon muonium addition. The signal has two components with very different relaxation rates, corresponding to two different spatial couplings of the Cu electron with the muonium's electron.

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“…Electron paramagnetic resonance, EPR, can provide powerful insights into the structure and properties of conducting polymers and has frequently been used to investigate the nature of various quasi-particles (Pratt et al, 1997;Salafsky, 1999;Chakrabarti et al, 1999;Chipara et al, 2003;Dennany et al, 2008Dennany et al, , 2010, such as excitons (Salafsky, 1999), solitons, polarons (Pratt et al, 1997), and bipolarons (Chakrabarti et al, 1999), which are thought to play a central role in charge transport. For example, a single resonance line located close to the g value of 2.003, is assigned to polaronic quasi-particles (Chipara et al, 2003;Kahol, 2000), while the zero spin bipolaron has s = 0 and hence is not EPR active (Yang and Li, 1993;Lippe and Holze, 1991).…”

Section: Epr Of the Pani-nf And Nanocompositementioning

confidence: 99%