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Utilizing organic electronics compatible with conventional semiconductor fabrication processes is extremely difficult because of their low chemical resistivity and poor environmental durability. To preserve the intrinsic functionality of organic materials, only a few fabrication processes can be used. Moreover, it is essential to achieve process expandability and silicon-process compatibility to develop high-resolution electronics suitable for mass production. Therefore, we developed wet-process-compatible organic photodetectors by replacing the conventional shadow-mask process with photolithography. This suppresses particle deposition during the serial fabrication processes, providing high operational stability. The fabricated green organic photodiodes exhibit a low dark current (1.0 × 10−11 A/cm2) with high photon–electron conversion efficiency (EQE = 65%). The charge collection and charge separation efficiencies are stable (ηcc = 84.6% and ηcs = 97.7%, respectively). Moreover, the organic semiconductors are compatible with conventional wet- and dry-etching processes owing to thin-film encapsulation layers. Finally, the novel organic image sensor can withstand 500 h under 85 °C/85% relative humidity and 1000 thermal cycles (−55–125 °C). Because of its robustness and strong barrier properties, the novel process architecture reported herein can be extended to any organic electronic devices, including widely commercialized organic light-emitting diodes and organic photovoltaic devices.

The electronic structure of low-lying unoccupied electronic states in a hexatriacontane ( n -C 36 H 74 ) thin film was directly observed using inverse photoemission spectroscopy (IPES). In the IPE measurements, it was confirmed that the hexatriacontane thin film is easily degraded by electron irradiation. Therefore by reducing the current density of the incident electrons gradually we finally obtained a reliable IPE spectrum free from radiation damage and/or surface charging. As a result, we conclude the IPE spectrum reported by Dudde and Reihl was influenced by radiation damage. The reliable spectrum shows two features near the vacuum level: they were not resolved in the reported spectrum. Further, it is compared with the reported results from other electron spectroscopies and theoretical calculations concerning the unoccupied electronic states in long chain alkanes.

Unoccupied electronic states of thin films of 3d-metal phthalocyanines (MPc: M=Mn, Fe, Co, Ni, Cu and Zn) and metal-free phthalocyanine (H 2 Pc) were investigated by inverse photoemission spectroscopy. The experimental results were analyzed with emphasis on the contribution of the 3d-metal orbitals to the lower unoccupied electronic states of MPc. The difference spectra between the sample MPc (M=Mn, Fe, Ni and Cu) and the reference ZnPc were found to be in fair agreement with the previously reported X-ray absorption spectra in the energy regions corresponding to the core excitation of the central metals. This shows that the difference spectra exhibit the partial density of states attributed to the central metals. A comparison of the 3d-metal orbital contributions was also made between the experimental difference spectra and reported results from extended Huckel and density functional calculations.

Inverse photoemission spectroscopy (IPES) in the vacuum ultraviolet region was applied to directly observe unoccupied electronic structures in a few kinds of organic thin films. The genuine IPE spectrum for the lowest unoccupied states in a long-chain alkane film was first obtained with a fairly low level of electron irradiation. The electronic structure around the energy gap in a perylene-3,4:9,10-tetracarboxylic dianhydride (PTCDA) film was examined by combining the observed IPE spectrum with previous ultraviolet photoemission spectra, to discuss its charge carrier characteristics. IPE measurements of PTCDA films were further extended to study electron injection behaviours due to alkali metal doping into those films, and by analysing the observed results the amount of injected electrons per molecule was evaluated with relation to the dopant concentration. The derived relationship has been explained with the aid of DV-Xα calculations of the energy levels concerned.

Ultraviolet photoemission (PE) and inverse photoemission (IPE) spectra were measured for thin films ofN,N′-dimethylperylene-3,4,9,10-bis(dicar☐imide) (DM-PBDCI) and perylene-3,4,9,10-tetracar☐ylic dianhydrite (PTCDA), the former known as an n -type organic semiconductor and the semiconducting nature of the latter still unidentified. The electronic structure around the energy gap, obtained from the combination of PE and IPE spectra observed, is found to be almost the same for the two compounds, indicating that PTCDA could be assigned as an n -type semiconductor.

Electronic structures of the unoccupied states in lithium phthalocyanine (LiPc) thin films of the x- and α-polymorphs were directly observed with inverse photoemission spectroscopy (IPES). The energy position of the lowest energy band and the lineshape of the second lowest energy band were different between the obtained IPE spectra for the two forms of the films. By comparing with energy levels in a LiPc molecule and its dimers calculated using the density functional method, we interpreted such differences as follows: the first band placed in lower energy for the α-form is due to more stabilized singly occupied molecular orbital (SOMO) and the observed splitting of the second feature for the x-form is lead from the removed degeneracy of 6eg levels caused by a large intermolecular interaction along the molecular stacking axis.

The spectral imaging for electroluminescence (EL) characterization in the light emitting diode (LED) based on blends of poly[2,7-(9,9-di-n-octylfluorene)] (PFO) and poly[2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)amino)-1,4-phenylene) ] (TFB) was performed using the two dimensional imaging micro-spectroscopy system. We found that EL spectral images varied with increasing applied voltages. The origin for such variation of EL spectral images will be discussed in this report.

In the course of the preparation of conductive molecular crystals using ‘percyano anions’, the molecular structure of HCDAH2- was revealed to be a planar geometry having a long diagonal line (≈ 10.4 Å). In (TTF)2(HCDAH)(CH3CN) [block-shaped TTF complex] (triclinic, P1, a = 8.258(5), b = 9.572(6), c= 10.070(4) Å, α = 89.89(5), β = 70.76(4), γ = 80.76(5)°, V = 740.7(7) Å3, Z = 2, final R-value = 0.074), the face-to-face type overlap between the side-byside arranged HCDAH dianions was observed. The donor packing pattern in (BEDOTTF) 6(HCDAH) (monoclinic, P21/a, a = 20.243(3), b = 4.086(1), c = 16.820(4) Å, b = 99.45(1)°, V = 1372.4(5) Å3, Z = 2/3, final R-value = 0.048) was determined to be HCP-type which is the second example in BEDO-TTF complexes.

Inverse photoemission (IPE) spectra of thin films of metal-free phthalocyanine (H 2 Pc), 3d-metal phthalocyanines (MPcs: M=Mn, Fe, Co, Ni, Cu and Zn) and lithium phthalocyanine (LiPc) have been measured to directly observe the electronic structures of their unoccupied states. In particular, IPE spectra of MPcs obtained systematically for 3d metals have been studied with the contribution from the 3d-metal orbitals to the electronic structures of the lower unoccupied states focused on. The difference spectra between MPcs (M=Mn, Fe, Co, Ni and Cu) and ZnPc as the reference are compared with the reported results from X-ray absorption spectroscopy as well as extended Huckel and density functional calculations to show that they reflect the density of unoccupied states derived from the central metals with permitting tentative assignments of their features.

The comparison of the crystal and electronic structures of the conducting BEDO-TTF salts between the different packing types characterizes the origin of the stabilization energy in each type. The importance of structural fitness between donor and counter components is demonstrated.