Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends

Miller, E. K.; Lee, Kwanghee; Hasharoni, Kobi; Hummelen, Jan C.; Wudl, Fred; Heeger, Alan J.

doi:10.1063/1.475550

Cited by 15 publications

(3 citation statements)

References 20 publications

(30 reference statements)

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“…121 Polymer/ nanocrystal blends are attracting attention for their potential applications in a wide range of electronic and optoelectronics devices such as light-emitting diodes 37,122 and photovoltaic devices 123 and nonlinear optical devices. 124,125 Electron transfer from polymers to nanocrystals is typically studied using photoluminescence quenching and photoconductivity. Detailed information about the transfer process, such as the spatial separation of holes and electrons and the underlying mechanisms for the transfer, is urgently needed.…”

Section: Nanoscale Electronic Devices: Experimental Challenges Nanocrmentioning

confidence: 99%

Electrical Scanning Probe Microscopy: Investigating the Inner Workings of Electronic and Optoelectronic Devices

Kuntze

Ban

Sargent

et al. 2005

Critical Reviews in Solid State and Materials Sciences

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Semiconductor electronic and optoelectronic devices such as transistors, lasers, modulators, and detectors are critical to the contemporary computing and communications infrastructure. These devices have been optimized for efficiency in power consumption and speed of response. There are gaps in the detailed understanding of the internal operation of these devices. Experimental electrical and optical methods have allowed comprehensive elaboration of input-output characteristics, but do not give spatially resolved information about currents, carriers, and potentials on the nanometer scale relevant to quantum heterostructure device operation. In response, electrical scanning probe techniques have been developed and deployed to observe experimentally, with nanometric spatial resolution, two-dimensional profiles of the electrical resistance, capacitance, potential, and free carrier distribution, within actively driven devices. Experimental configurations for the most prevalent electrical probing techniques based on atomic force microscopy are illustrated with considerations for practical implementation. Interpretation of the measured quantities are presented and calibrated, demonstrating that internal quantities of device operation can be uncovered. Several application areas are examined: spreading resistance and capacitance characterization of free carriers in III-V device structures; acquisition of electric potential and field distributions of semiconductor lasers, nanocrystals, and thin films; scanning voltage analysis on diode lasers-the direct observation of the internal manifestations of current blocking breakdown in a buried heterostructure laser, the effect of current spreading inside actively biased ridge waveguide lasers, anomalously high series resistance encountered in ridge lasers-as well as in CMOS transistors; and free-carrier measurement of working lasers with scanning differential spreading techniques. Applications to emerging fields of nanotechnology and nanoelectronics are suggested.

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Section: Nanoscale Electronic Devices: Experimental Challenges Nanocrmentioning

confidence: 99%

Electrical Scanning Probe Microscopy: Investigating the Inner Workings of Electronic and Optoelectronic Devices

Kuntze

Ban

Sargent

et al. 2005

Critical Reviews in Solid State and Materials Sciences

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“…11 Composites of conducting polymers such as poly͑3-alkylthiophene͒ ͑P3AT͒, poly͑p-phenylenevinylene͒ ͑PPV͒ derivatives and PFO, and highelectron affinity species such as fullerene ͑C 60 ͒ and C 60 derivatives have been investigated extensively, because highly efficient photoinduced charge separation occurs in the polymer-C 60 composites upon C 60 doping, which is useful to develop the efficient nonlinear optical and photovoltaic devices. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] This charge separation is attributed to photoinduced electron transfer from polymer to C 60 , which forms positive charges on polymer chains and radical anions of C 60 molecules, respectively. The positive charge carriers on conjugated polymers are considered to be polarons, 1 however, the nature of the polaronic states has not yet been completely clarified.…”

Section: Introductionmentioning

confidence: 99%

Electron spin resonance and electron nuclear double resonance of photogenerated polarons in polyfluorene and its fullerene composite

et al. 2009

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Electron spin resonance ͑ESR͒ and electron-nuclear double resonance ͑ENDOR͒ of photogenerated polarons in poly͑9,9-dioctylfluorene͒ ͑PFO͒ and its composite with fullerene ͑C 60 ͒ using variable photoexcitation energy up to 4.1 eV are reported. For PFO, a light-induced ESR ͑LESR͒ signal ͑g = 2.003͒ is observed below 60 K, and its transient response and excitation spectrum indicate that the observed spins are photogenerated polarons on PFO. For the PFO-C 60 composite, two LESR signals of photogenerated positive polarons on PFO ͑g 1 = 2.003͒ and radical anions on C 60 ͑g 2 = 1.999͒, respectively, are observed below 120 K, which are caused by photoinduced electron transfer from PFO to C 60. A remarkable enhancement of the LESR signals in the excitation spectrum at ϳ2.8 eV is observed compared with the case of pure PFO. The bimolecularrecombination kinetics of photogenerated charge carriers in the composite are confirmed by the dependence of the LESR on excitation-light intensity and by the decay dynamics. Light-induced ENDOR ͑LENDOR͒ signals are clearly observed for excitation around 2.8 eV owing to the highly efficient photoinduced electron transfer in the composite. Broad LENDOR shifts directly reflect the spin-density distribution of the polarons in PFO. We have determined its maximum shift using LENDOR-induced ESR, and have evaluated the maximum spin density on the carbon site coupled to the proton as 0.032. This value is consistent with the theoretical result obtained by Pariser-Parr-Pople ͑PPP͒ model, where the spatial extent of the polarons is calculated as ϳ3 monomer units of PFO. The calculated LESR spectra of PFO based on the PPP model are consistent with the experimental spectra, which confirm the above spatial extension of the polaron in PFO.

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“…15 Alkyl-substituted and high molecular-weight poly (1,4-phenylenevinylene)s have been prepared via the appropriate polymerization routes. The high molecular weight and aminium radical-substituted poly- (1,4-phenylenevinylene)s are expected to be a new y To whom correspondence should be addressed (Tel: +81-3-3200-2669, Fax: +81-3-3209-5522, E-mail: nishide@waseda.jp).…”

mentioning

confidence: 99%

Triarylamine-Bearing Poly(1,4-phenylenevinylene): Facile Preparation and Its Durable Aminium Polyradical

Kurata

Nishide

2007

Polym J

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ABSTRACT:Poly[2-{bis(4-methoxyphenyl)amino}phenyl-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] 1 was prepared via the Gilch reaction of the p-bis(chloromethyl)benzene monomer, 2-{bis(4-methoxyphenyl)aminophenyl}-, 0 -dichloro-p-xylene. The Gilch reaction facilitated the preparation of the polyphenylenevinylene with a triarylamine pendant group when compared to that via the Heck polycondensation. The molecular weight of the polymer was approximately 4:0 Â 10 5 , and it was soluble in common solvents and was reversibly redoxed due to the pendant arylamine moiety. Chemical oxidation of 1 afforded the corresponding aminium polyradical 1 þ with the half life-time of ca. 2 weeks under ambient conditions. ESR and magnetization measurements of 1 þ revealed a forbidden multiplet signal and an average spin quantum number (S) of 3/2 at low temperature, respectively. The polyradical 1 þ was the first example of a high molecular weight, high-spin organic polymer with solvent-solubility and film formability. 2,3-Bis[N,N-bis(4-methoxyphenyl)aminophenyl]stilbene 2 and its aminium diradical 2 þ were also prepared as the model dimer compounds; 2 þ was a triplet molecule at low temperature. The effect of the %-conjugated poly(1,4-phenylenevinylene) backbone on the high-spin alignment was also discussed. [doi:10.1295/polymj.PJ2006226] KEY WORDS Poly(phenylenevinylene) / Gilch Reaction / Aminium Radical / High-Spin Molecule / %-Conjugated Polymer / Radical Polymer / %-Conjugated and high-spin radical polymers have drawn the attention of researchers due to the possible creation of a purely organic-derived magnetic material.1,2 The target radical polymers have been molecular-designed by satisfying a non-Kekulé and nondisjoint fashion upon the %-conjugated connectivity among the radical moieties in order to realize an effective overlap of singly occupied molecular orbitals and a strong ferromagnetic interaction of the unpaired electrons of the radical moieties.1,3 Rajca et al. synthesized a two-dimensionally macrocyclic polyradical, poly(1,3-phenylenephenylmethine), and succeeded in producing very high magnetic moments and a spin quantum number (S > 5400) at very low temperature. 4 However, the arylmethine radical did not exist above 200 K, which prevents further development of the high-spin organic polymer.A triarylaminium radical possesses a high durability under ambient conditions due to the delocalized unpaired electron, which could also contribute to an efficient spin-exchange interaction in the molecule. Recently, we succeeded in synthesizing a durable poly(1,2-phenylenevinylene anisylaminium) derivative with a molecular weight of several thousands, in which the stilbene linker worked as an effective ferromagnetic spin coupler through the extended %-conjugated structure to give S of 3/2-7/2 at room temperature. 5,6 Such durable radical-bearing %-conjugated polymers possess a solvent solubility and tolerance for the spin-defect because the pendant spins are expected to interact not only with neighboring, but also with discrete spin...

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Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends

Cited by 15 publications

References 20 publications

Electrical Scanning Probe Microscopy: Investigating the Inner Workings of Electronic and Optoelectronic Devices

Electrical Scanning Probe Microscopy: Investigating the Inner Workings of Electronic and Optoelectronic Devices

Electron spin resonance and electron nuclear double resonance of photogenerated polarons in polyfluorene and its fullerene composite

Triarylamine-Bearing Poly(1,4-phenylenevinylene): Facile Preparation and Its Durable Aminium Polyradical

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