Substitutional n-Type Doping of an Organic Semiconductor Investigated by Electron Paramagnetic Resonance Spectroscopy

Chen, Si-Guang; Branz, Howard M.; Taylor, P. C.; Cormier, Russell A.; Gregg, Brian A.

doi:10.1021/jp049628c

Cited by 47 publications

(66 citation statements)

References 37 publications

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“…À was similar to that of other PDI radical anions, [22][23][24] with an overall peak-to-peak width of 4.4 G, the EPR linewidths, DH, of the dimers, trimer, and tetramer were narrower than that of the monomer (Table 1). All radical anions had a measured g factor of 2.0026 AE 0.0001, which is typical for organic aromatic molecules.…”

supporting

confidence: 77%

“…[23,24] The ENDOR spectrum of 2 oC À also has two paired lines, but with splittings of 2.1 and 1.3 MHz, which are just slightly larger than half those observed for the monomer. Thus, electron hopping between the P moieties must occur at a rate higher than 10 7 s À1 .…”

Section: Mhz (1-h 6-h 7-h 12-h) and 28 Mhz (2-h 5-h 8-h 11-h)mentioning

confidence: 88%

“…This idea is consistent with the observation that even in non-DNA PDI systems with a much longer aggregation length, CW EPR line narrowing has previously been observed only down to about 2.3 G, the equivalent of three to four PDI units. [22,23] However, the UV/ Vis spectra of 2C…”

Section: Mhz (1-h 6-h 7-h 12-h) and 28 Mhz (2-h 5-h 8-h 11-h)mentioning

confidence: 99%

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Electron Hopping among Cofacially Stacked Perylenediimides Assembled by Using DNA Hairpins

et al. 2010

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The self-assembly of redox-active molecules into ordered arrays capable of rapid, long-distance charge transport is important for the development of functional nanomaterials for organic electronics. In this regard, DNA shows great promise as a structural scaffold for the helical arrangement of chromophores and other (semi)conducting materials. [1][2][3] Base substitutions and modifications, sugar modifications, and noncovalent interactions have all been used for the construction of such DNA-based structures. Perylenediimides (PDIs), which have the advantages of strong absorptivity, high fluorescence quantum yields, high photochemical and thermal stability, strong hydrophobic p-p stacking interactions, and semiconducting properties, have been incorporated in a variety of structures. [4][5][6][7][8][9][10][11][12][13][14][15][16] Recently, Wagner and Wagenknecht [10] reported the preparation of a PDI derivative, P (Figure 1), which is readily incorporated into an oligonucleotide and serves as a base-pair surrogate when located opposite an abasic site in a duplex structure. The incorporation of P in opposite complementary oligonucleotides has been shown to result in the formation of stable duplexes in which the P units are located in a zipperlike fashion within the hydrophobic interior of the resulting duplex. [5,17] The stacking of P units within the duplex resulted in an excimer-like state following photoexcitation. [16] We report herein the results of our investigation of intramolecular electron hopping within a series of synthetic DNA hairpins 1-4 (Figure 1). These hairpins possess compact 3'-CCA loop regions connecting poly(T)-poly(A) stems containing a single P moiety located opposite an abasic site (1), two P moieties located opposite abasic sites and attached either to the same strand (in 2 s) or to opposite strands (in 2 o), or three or four P moieties positioned adjacent to one another but on opposite strands in a zipperlike fashion (in 3 and 4). The EPR spectra of the singly reduced duplexes were consistent with electron hopping between two sites in both dimers (the hairpins containing two P moieties) and the trimer 3, and among three sites in the tetramer 4. Herein, we discuss the origin and implications of partial electron sharing.Oligonucleotides containing P were synthesized by the method of Wagner and Wagenknecht; [10] the CCA linker in hairpins 1-4 has been employed previously in the synthesis of stable minihairpins. [13,17,18] The characterization of 1-4, including mass spectrometry and circular dichroism (CD), is described in the Supporting Information.An intensity reversal was observed in the UV/Vis absorption spectra for the 0!0 and 0!1 transitions in 2-4 with respect to those of 1 (Figure 2). This result indicates that the p-stacked P chromophores are exciton-coupled. [19][20][21] Moreover, the A 0!0 /A 0!1 ratio for the vibronic bands decreased as the number of P units increased, and there was a notable difference between dimers 2 s and 2 o, presumably as a result of the conformational changes...

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supporting

confidence: 77%

Section: Mhz (1-h 6-h 7-h 12-h) and 28 Mhz (2-h 5-h 8-h 11-h)mentioning

confidence: 88%

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Electron Hopping among Cofacially Stacked Perylenediimides Assembled by Using DNA Hairpins

et al. 2010

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“…It is important to be aware that the measured spin concentration is not necessarily equivalent to the radical product yield because of possible spin-pairing, broadening, or quenching effects. 23 However, the observation of a linear relationship between the dopant and spin concentrations indicates the formation of the latter may be attributed to the former, and the substantial amount of spin present implies that the fullerene radicals are not minor byproducts of the doping reaction. This conclusion was further substantiated by the UV–vis–near-IR spectra of doped solutions of PC 61 BM.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Study on the Solution-Phase n-Doping of 1,3-Dimethyl-2-aryl-2,3-dihydro-1H-benzoimidazole Derivatives

et al. 2013

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The discovery of air-stable n-dopants for organic semiconductor materials has been hindered by the necessity of high-energy HOMOs and the air sensitivity of compounds that satisfy this requirement. One strategy for circumventing this problem is to utilize stable precursor molecules that form the active doping complex in situ during the doping process or in a postdeposition thermal- or photo-activation step. Some of us have reported on the use of 1H-benzimidazole (DMBI) and benzimidazolium (DMBI-I) salts as solution- and vacuum-processable n-type dopant precursors, respectively. It was initially suggested that DMBI dopants function as single-electron radical donors wherein the active doping species, the imidazoline radical, is generated in a postdeposition thermal annealing step. Herein we report the results of extensive mechanistic studies on DMBI-doped fullerenes, the results of which suggest a more complicated doping mechanism is operative. Specifically, a reaction between the dopant and host that begins with either hydride or hydrogen atom transfer and which ultimately leads to the formation of host radical anions is responsible for the doping effect. The results of this research will be useful for identifying applications of current organic n-doping technology and will drive the design of next-generation n-type dopants that are air stable and capable of doping low-electron-affinity host materials in organic devices.

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“…The long axes of these 1D structures are feasible for long-range exciton diffusion when exposed to light 19,20 and for electron transport after an electron-transfer process from electron donors. 21,22 Such features of 1D nanostructures of PDI have led to various applications. For example, n-type semiconducting properties of PDI nanowires have been utilized in organic field effect transistors [23][24][25] and phototransistors.…”

mentioning

confidence: 99%

Energy and Electron Transfer of One-Dimensional Nanomaterials of Perylenediimides

Supur¹,

Fukuzumi²

2013

ECS J. Solid State Sci. Technol.

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This review describes the photodriven energy-and electron-transfer processes of the columnar perylenediimide (PDI) nanostructures for efficient light-energy conversion by employing the self-assembly models. The charge separation and the directional charge transport of the oligomers, aggregates, and one-dimensional (1D) nanostructures of PDIs have been clarified by using time-resolved transient absorption techniques. Excited states, exciton migration, and excitation energy-transfer processes were examined in the first part. The second part involves the electron hopping, photodriven electron transfer and transport events taking place within the various PDI nanostructures.Unique light-harvesting and redox properties together with high chemical, thermal and photostability make perylenediimides (PDIs) the essential building blocks of energy and electron donor-acceptor systems. One important feature of PDI is its large π-plane enabling the π-π interactions for self-assembly. 1 PDIs can form one-dimensional (1D) nanostructures by supramolecular self-assembly in the solution as a low-cost, affordable bottom-up method. 2-4 The length of PDI nanofibrils can reach about 0.3 mm due to strong π-stacking in 'poor' solvents. 5 Other than the solvophobic effects, 6-8 hydrogen bonding 9-12 and ionic interactions 13-15 assisting π-π interactions have been used to fabricate nanoscale materials of PDIs in one dimension. Coupled crystallization of PDI with proper polymer templates by solvent evaporation 16 and chemical-reaction mediated self-assembly in the solution 17,18 are the other convenient bottom-up methods for the fabrication of 1D nanofibers of PDI. The long axes of these 1D structures are feasible for long-range exciton diffusion when exposed to light 19,20 and for electron transport after an electron-transfer process from electron donors. 21,22 Such features of 1D nanostructures of PDI have led to various applications. For example, n-type semiconducting properties of PDI nanowires have been utilized in organic field effect transistors 23-25 and phototransistors. 26 Nanostructures of PDIs have also been widely used in the sensing applications for nitrobased explosives, 27 organic amines, 28 and nitrogen-based reducing agents. 29,30 Their photovoltaic properties have been also reported. 31,32 There have been many comprehensive reviews regarding the fabrication methods and the applications of 1D nanostructures of PDIs together with various organic materials, some of which are already referred in this review. [2][3][4]11 Besides these aspects, elucidation of the fundamental energy and electron-transfer events taking place within the PDI nanostructures is also of importance to improve the quality and efficiency of the current applications and to rationalize the future design of the related devices. This review will basically focus on the photoinduced energy-and electron-transfer processes occurring in the aggregates and nanostructures of PDIs, which mainly have 1D geometry. Photoinduced processes of supramolecular oligomeric an...

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Substitutional n-Type Doping of an Organic Semiconductor Investigated by Electron Paramagnetic Resonance Spectroscopy

Cited by 47 publications

References 37 publications

Electron Hopping among Cofacially Stacked Perylenediimides Assembled by Using DNA Hairpins

Electron Hopping among Cofacially Stacked Perylenediimides Assembled by Using DNA Hairpins

Mechanistic Study on the Solution-Phase n-Doping of 1,3-Dimethyl-2-aryl-2,3-dihydro-1H-benzoimidazole Derivatives

Energy and Electron Transfer of One-Dimensional Nanomaterials of Perylenediimides

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