Tunneling-Current-Induced Light Emission from Copper Phthalocyanine Thin Films

Uemura, Tomomasa; Furumoto, Masako; Nakano, Takeshi; Akai‐Kasaya, Megumi; Aono, Masakazu; Saitô, Akira; Kuwahara, Yuji

doi:10.1380/ejssnt.2006.559

Cited by 6 publications

(2 citation statements)

References 22 publications

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“…Recently, however, it has been found that an ultrathin oxide layer [4,6] or multiple organic layers [7] prevented the transfer of nonradiative energy to a metal substrate and that a tip-induced plasmon (TIP) on a noble-metal surface increased the QE of STM-induced molecular fluorescence. [8,9] These effects facilitate the observation of fluorescence from organic molecules.…”

Section: Introductionmentioning

confidence: 99%

Spatially resolved detection of plasmon‐enhanced fluorescence using scanning tunneling microscopy

Uemura

Akai‐Kasaya

Saitô

et al. 2008

Surface & Interface Analysis

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Section: Introductionmentioning

confidence: 99%

Spatially resolved detection of plasmon‐enhanced fluorescence using scanning tunneling microscopy

Uemura

Akai‐Kasaya

Saitô

et al. 2008

Surface & Interface Analysis

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“…[2][3][4][5][6][7][8][9][10][11][12] Studies on the STML of organic molecules have attracted much attention since it enables to investigate the optical properties of those molecules at nanometer scale and provides useful information to develop the organic light emitting diode devices in the future. [13][14][15][16][17][18][19][20][21] Hoffmann et al 22 observed light emission from single hexa-tert-butyldecacyclene molecules on noble-metal surfaces. They found that the emission spectra are indicative of plasmon-mediated emission of the metal substrate and tip, while the molecule slightly modifies the plasmon emission.…”

Section: Introductionmentioning

confidence: 99%

Bias dependence of tunneling-electron-induced molecular fluorescence from porphyrin films on noble-metal substrates

Liu

Nishitani

et al. 2007

Phys. Rev. B

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We investigated scanning tunneling microscope ͑STM͒-excited luminescence from porphyrin ͑PhTPP and H 2 TPP͒ thin films on metal substrate ͑Au and Ag͒ under ambient conditions. Molecular fluorescence similar to the corresponding photoluminescence was observed from PhTPP/Au and H 2 TPP/ Ag at both STM bias polarities. We found that at the same experimental condition and parameters, the STM-induced luminescence intensities of maxima peak are similar for PhTPP and H 2 TPP but weaker by a factor of about 4 than that for H 2 TBPP which we studied previously, probably due to fluorescence quenching by aggregation. The polarity dependence and the bias voltage dependence of the fluorescence intensity for the PhTPP/Au were similar to that for the respective pristine metal. These facts support our proposal that intense molecular fluorescence from porphyrin film on the noble metals is a result of the enhancement of molecular excitation by substrate surface plasmons.

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Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

Guo

Yan

2008

Advanced Materials

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Novel copper phthalocyanine (CuPc) materials have potential applications in solar cells, fuel cells, optical-limiting materials, gas sensors and field-effect transistors. [1][2][3][4][5][6][7][8][9][10] Most recently there have been interests in applications for high dielectric constant material for capacitors. [11,12] For example, Zhang et al. have reported a dielectric constant of $48 at 1 MHz in an electrostrictive polymeric CuPc/Polyvinylidenefluoridetrifluoroethylene-chlorofluoroethylene P(VDF-TrFE-CFE) composite.[11] However, a relatively high dielectric loss (>0.4) exists in such system due to the percolation limit of the CuPc filler. More recently, we have observed a very high intrinsic dielectric constant, coupled with a small dielectric loss (<0.01 up to 1MHz) in a newly developed hyper-branched CuPc dendrimer. [12] Although numerous reports have demonstrated the dielectric performance of CuPc polymers, the understanding of the electronic and optical behavior in dendrimers is limited, which is essential in the development of new materials. In this communication, the charge carrier mobility of a newly developed CuPc dendrimer is investigated. The synthesis of the CuPc dendrimer has been previously reported and is shown in Scheme 1. [12] This hyper-branched CuPc has dendritic-like structure consisting of four -CN groups incorporating into the CuPc core. Moreover, our previous experience in the study of triarylamine-based dendrimers and ladder oligomers using the ultra-fast spectroscopy suggested a coherent energy migration process occurred and polaron delocalization states are possible.[13] Time-resolved spectroscopy measurement has been carried out to study the optical behavior of this dendrimer. Our investigation has suggested the formation of delocalized polarons in the system. The super-conjugation effect from the oxygen atom and an increase of system packing through the self-assembling of phthalocyanine rings give polaron hopping and polaron tunneling between phthalocyanine rings. In order to probe the electronic properties of this dendrimer, we carried out time-of-flight measurements to investigate the electron mobility. CuPc dendrimer was first dissolved in N, N-dimethylacetymide (DMAc) solution at a concentration of 1 mg mL À1, then the CuPc/DMAc solution was drop-cast on a silicon wafer with a thickness of 500 mm. After drying in a vacuum oven at 120 8C for several hours, a dendrimer film with a thickness ranging between 4 to 5 mm was obtained using a surface profiler. Further details of the procedure are in the experiment section.A typical transient current at an applied field of 5 V at several different temperatures is depicted in Figure 1 plotted on a linear scale. The transient current signals at room temperature follow a plateau region after a fast decay, then slowly tail off. This shows the characteristics of non-dispersive charge carrier transport. However, upon lowering the temperature, an apparent transition from non-dispersive to dispersive charge carrier transport occurs, which indicat...

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Tunneling-Current-Induced Light Emission from Copper Phthalocyanine Thin Films

Cited by 6 publications

References 22 publications

Spatially resolved detection of plasmon‐enhanced fluorescence using scanning tunneling microscopy

Spatially resolved detection of plasmon‐enhanced fluorescence using scanning tunneling microscopy

Bias dependence of tunneling-electron-induced molecular fluorescence from porphyrin films on noble-metal substrates

Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

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