Hole transporting behavior of two fluorene derivatives having carbazole group (2C1CBz) and diphenyl amino group (2C1DAF) and a carbazole derivative (C2CBzCBz) were investigated. Further, the fluorene derivatives and typical hole-transporting materials, 4,4’-bis[N-(p-tolyl)-N-phenyl-amino] biphenyl (TPD) and 4,4'-Bis(carbazol-9- yl)biphenyl (CBP) was analyzed based on the Gaussian Disorder Model. At room temperature, amorphous film of 2C1CBz exhibited highest hole mobility of 3.1 x 10-3 Vcm2/Vs at 1.6 x 105 Vcm-1 in these materials. From analysis based on the Gaussian Disorder Model, however, amorphous film of CBP is indicated to have highest disorder free mobility; the values of 2C1CBz, 2C1DAF, CBP and TPD were 0.812, 0.092, 2.84, and 0.38 cm2/Vs, respectively. In addition, their reorganization energy / was evaluated by a quantum mechanical calculation with ADF (Amsterdam Density Functional package, Scientific Computing and Modeling Co.) based on the Marcus theory. The experimental and calculation results demonstrated that the u0 has good proportionality relation with the /. Because theu0 mean as a rough standard of carrier-transporting, this result suggest that evaluation of / may be a promising approach to design molecular structure of carrier transporting materials with high carrier mobility.
Propyl ammonium bromide C3, carbazole-linked and naphtalen-linked ammonium bromides CBz and Nap, and PbBr2Pb were dissolved in dimethylformamide (DMF) at the molar ratio of C3:CBz:Pb and C3:Nap:Pb = 2:0:1, 4:2:3, 1:1:1, 2:4:3, and 0:2:1. The thin films were prepared on fused quartz substrates by spin-coating from the DMF solutions. Super layer structure, where organic dielectric layer, inorganic semiconductor layer, and organic semiconductor are assembled in order, was successfully constructed by a simple spin-coating with the solution in which propyl ammonium bromide C3, carbazole-linked propyl ammonium bromide CBz, naphthalene-linked ammonium bromides Nap and PbBr2Pb (the molar ratio;C3 : CBz : Pb and C3 : Nap : Pb= 4 : 2: 3) were dissolved .
In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabricate disposable photodiodes as
the detectors on the integrated lab-on-chip lasers. J-aggregated films of a cyanine dye, NK-1952 doped into a conductive
polymer, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) on the indium tin oxide (ITO)
substrate have made by the ink-jet method, respectively. With the thin Al layer on the top of cyanine dye films as the
cathode, while ITO substrate as the anode, the photodiodes have been demonstrated to be wavelength sensitive under the
excitation of a tunable pico-second laser, which corresponds to the characteristic red-shifted, sharp and narrow J-aggregate
absorption peak of each cyanine dye employed. The influence of ink-jet fabrication parameters, presence of
metal ions and pH value of dye solutions on the J-aggregate formation and also the wavelength sensitivity of the
photodiodes have been systematically investigated and the mechanisms involved have been discussed. It is found that by
optimizing the ink-jet fabrication parameters such as UV exposure dose amount, and substrate temperature, or by
introducing ions such as K+, Na+, or H+, the wavelength resolution of the ink-jet printed photodiodes can be improved
significantly, and wavelength resolution of less than 0.1nm may be expected.
The effect of charge carrier mobilities on EL performances in electroluminescent diodes were discussed. It is stressed that quantum EL efficiency is no direct relation with charge mobilities but power efficiency may concern with charge carrier transport processes, because power efficiency is inversely proportional to drive voltage. Hole and electron mobility data on both bulk films and polymer-dispersed films were summarized and some discussions on the relation between molecular structures and charge mobilities were added. In addition, the meaning of designing high mobility materials for EL diodes is discussed. Our recent studies on the introduction of molecular alignment by use of liquid crystalline textures for the increase of charge mobilities were mentioned.
Survey of dye materials for the emission layer in the multilayer organic electroluminescent (EL) device is discussed in terms of emission color and fluorescent efficiency. Organic semiconductors for the electron or the hole transport layer in the EL device are proposed for preparing stable homogeneous thin layer. Requirement of accomplishing the confinement of the singlet excitons generated by the recombinations of injected electrons and holes is discussed by using three layer EL devices with extremely thin bimolecular emission layer. Then the emphasis is laid on the size effects in three layer EL device with double heterojunctions on the spontaneous emission. Variations of the intensity and pattern of outer emission through semitransparent ITO glass substrate with the spacing between the emission layer and the metallic electrode are discussed theoretically and experimentally. And variation of the fluorescent lifetime or the radiative decay rate with the spacing is also discussed theoretically and experimentally.
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