Dielectric properties of Cu-phthalocyanine systems from first principles

Shi, Ning; Ramprasad, Rampi

doi:10.1063/1.2339037

Cited by 28 publications

(32 citation statements)

References 16 publications

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“…55,56 These orientation effects can be observed in transport measurements, as recently reported in ultrathin copper phthalocyanine vertical heterojunctions. 55,56 Orientation of molecule adsorbed on gold NP is easily observed using LSPR as demonstrated on a calcium modulated plasmonic switch in which protein conformation changes induced by calcium bindings was easily detected. 57 Such effects are also at the origin of the design of active plasmonic devices using liquid crystals because of their large refractive index anisotropy.…”

Section: ■ Results and Discussionmentioning

confidence: 81%

Tunable Plasmon Resonance of Gold Nanoparticles Functionalized by Electroactive Bisthienylbenzene Oligomers or Polythiophene

et al. 2014

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We investigate the effect of new redox molecular switches based on oligothiophene deposited on gold nanoparticles (AuNPs) as thin electroactive layers in the 5−80 nm thickness range. In doing so, we compare systems based on physisorbed electroactive layers (weak electronic coupling) with those based on covalently bonded layers (strong electronic coupling), and we investigate orientation and thickness effects. Two different deposition methods were used. The first is based on bithiophene electropolymerization and the second on diazonium salt electroreduction. In both cases, redox switching of the electroactive layer makes is possible to tune the plasmonic properties of the AuNPs, and the layer thickness has a strong impact on the amplitude of the localized surface plasmon resonance (LSPR) modulation. LSPR modulation upon redox switching also depends on the electronic coupling regime between the AuNP and the organic layer. Indeed, the apparent real part of the dielectric constant seen by the AuNP is larger when oligothiophenes are covalently bonded to the AuNPs. Moreover, the LSPR wavelength, in the 700−750 nm range, shifts in the opposite direction upon redox switching of the organic layers in weak or in strong electronic interaction with the AuNPs. These behaviors may be attributed to orientation effects, but also suggest that, in a strong electronic coupling regime, plasmon delocalization within the covalently grafted conducting organic material is enhanced. ■ INTRODUCTIONA large variety of nanometer-scale devices have been investigated in recent years because of the continuously increasing demand for ultimate miniaturization of electronic and photonic systems. Among these, devices based on gold nanoparticles (AuNPs) are well-known for their remarkable properties. Indeed, AuNPs smaller than the incident light wavelength exhibit coherent oscillations of the confined free electrons in their conduction bands. When the frequency of these collective electron oscillations coincides with that of the excitation light, a resonance phenomenon appears and strong absorption in the visible range occurs. The frequency of this socalled localized surface plasmon resonance (LSPR) depends on the size of the NPs, their shape, the distance between them, and the dielectric constant of the surrounding medium. Such LSPR enhances electric fields very close to the NP structures and allows the manipulation of light and its interaction with matter at the nanoscale. In this sense NPs work in a similar way to that of antennas in radio and telecommunication systems, but at optical frequencies, i.e., at frequencies corresponding to typical electronic excitations in matter. Such NP-based systems are part of the emerging scientific domain of plasmonics which offer an opportunity to merge photonics and electronics at nanoscale dimensions to obtain unusual properties for unprecedented levels of synergy between optical and electronic functions. Plasmonic devices such as waveguides, 1−3 filters, 4,5 polarizers, 4,6 light sources, 7 lenses, 8,9 and a...

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Section: ■ Results and Discussionmentioning

confidence: 81%

Tunable Plasmon Resonance of Gold Nanoparticles Functionalized by Electroactive Bisthienylbenzene Oligomers or Polythiophene

et al. 2014

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“…This dielectric constant appears to be larger than reported values ͑2-7͒, 30-33 but on the other hand, larger r values of 10-20 have also been suggested because CuPc is a polar molecule. 34 Furthermore, the J value can be explained using a typical r value of 3.5 if a larger mobility of 6 ϫ 10 −3 cm 2 / ͑V s͒, which is still realistic, is used. These estimations suggest that the large current in Fig.…”

Section: Energy Level Alignments Of Npb/ Cu 17 Se and Cupc/ Cu 1mentioning

confidence: 99%

Characterization of copper selenide thin film hole-injection layers deposited at room temperature for use with p-type organic semiconductors

Hiramatsu

Koizumi

Kim

et al. 2008

Journal of Applied Physics

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Copper selenide, CuxSe(x∼2), was examined as a hole-injection layer for low-temperature organic devices. Crystalline CuxSe films grown at room temperature with atomically flat surfaces exhibited metallic conduction with a high electrical conductivity of 4.5×103 S/cm, a hole concentration of 1.4×1022 cm−3, and a mobility of 2.0 cm2/(V s). Analysis of the free carrier absorption using the Drude model estimated the effective mass of a hole as 1.0me. Photoemission spectroscopy measurements of the interfaces between CuxSe and organic hole transport layers, N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl) benzidine (NPB) and copper phthalocyanine (CuPc), verified that the hole-injection barriers of these interfaces (0.4 eV for NPB and 0.3 eV for CuPc) are smaller than that of a conventional indium tin oxide (ITO) hole-injection electrode/NPB interface (0.6 eV) but are comparable to that of an ITO electrode/CuPc interface (0.3 eV). Hole-only devices using the CuxSe layer as a hole-injection anode exhibited very low threshold voltages (0.4–0.5 V) and nearly Ohmic characteristics. The NPB layer on the CuxSe layer was found to be highly doped at 1017–1019 cm−3, probably due to copper diffusion, while the CuPc layer is nearly intrinsic with a doping concentration lower than 1015 cm−3. These results indicated that a CuxSe film combined with CuPc is a promising candidate for a low-voltage hole-injection anode or a buffer layer in low-temperature devices such as organic light-emitting diodes and thin film transistors.

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“…10 In both of these cases, the results reveal relatively low dielectric constants of isolated CuPc monomers: 15 along the plane and 2-3 perpendicular to the plane of the monomer, considerably lower than the value of several hundreds reported for CuPc-polymer composites. 6,8,9 In this contribution, we present a systematic study of structural, electronic, and dielectric properties of vertical stacks of CuPc and H 2 Pc monomers and sheets, based on density-functional theory ͑DFT͒. The primary motivation for studying the stacked variety of monomeric and polymeric sheets of CuPc and H 2 Pc is twofold.…”

Section: Introductionmentioning

confidence: 99%

“…7 Our recent study has established an initial understanding of the dielectric properties of isolated phthalocyanine ͑Pc͒ based monomer molecules. 8,9 We have computed the dielectric constant of isolated CuPc monomers using both a semiclassical method 8 and a fully quantum-mechanical method 9 based on a recently developed theory of the local dielectric permittivity. 10 In both of these cases, the results reveal relatively low dielectric constants of isolated CuPc monomers: 15 along the plane and 2-3 perpendicular to the plane of the monomer, considerably lower than the value of several hundreds reported for CuPc-polymer composites.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic dielectric properties of phthalocyanine crystals: Anab initioinvestigation

Shi

Ramprasad

2007

Phys. Rev. B

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Cu phthalocyanine ͑CuPc͒ based composites are expected to display high dielectric constants, of the order of several hundreds, based on recent experimental work. In an attempt to determine whether CuPc has a high dielectric constant intrinsically, and if so, in order to identify the circumstances under which such high dielectric constants could result, a systematic ab initio study is undertaken. This study extends prior work on the intrinsic dielectric properties of isolated CuPc and the closely related H 2 phthalocyanine ͑H 2 Pc͒ monomers. The tendency of CuPc and H 2 Pc monomers and polymeric sheets to stack is critically assessed, and the concomitant changes in the electronic and optical properties as a function of the stacking distance are determined. Our results indicate that both CuPc and H 2 Pc systems exhibit an insulator to metal transition as the stacking distance approaches 3 Å ͑the equilibrium spacing͒. Consistent with this behavior, the dielectric constant reaches large values as the stacking distance approaches 3 Å, while it is small for larger stacking distances, in accord with our prior estimates.

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Dielectric properties of Cu-phthalocyanine systems from first principles

Cited by 28 publications

References 16 publications

Tunable Plasmon Resonance of Gold Nanoparticles Functionalized by Electroactive Bisthienylbenzene Oligomers or Polythiophene

Tunable Plasmon Resonance of Gold Nanoparticles Functionalized by Electroactive Bisthienylbenzene Oligomers or Polythiophene

Characterization of copper selenide thin film hole-injection layers deposited at room temperature for use with p-type organic semiconductors

Intrinsic dielectric properties of phthalocyanine crystals: Anab initioinvestigation

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