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The fabrication and characteristics of bulk-heterojunction organic photodetectors (OPDs) toward near-infrared narrowband-light detection devices are investigated. For conventional OPDs with thick active layers based on poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester blends, increasing the PCBM concentration leads to the improvement of near-infrared detection. For inverted devices, the improvement of near-infrared detection can be achieved by varying bulk-heterojunction. The inverted OPD with a thicker active layer shows a spectral response with a maximum peak of approximately 760 nm and an IPCE of above 40 % at −5 V.

Circular cavity structures are fabricated on GaAs/ AlGaAs-based epi-wafer using SiO x hard mask to realize a proposed photonic crystal (PhC) structure with GaAs core layer having embedded InAs quantum dots (QDs) towards PhC laser fabrication. We investigate the evaluations of selective dry etching of the core layer for an epi-wafer using optical measurements. Photoluminescence (PL) intensity at 1285 nm, which is related to ground-state emission of QDs, monotonously decreases with increasing the etching depth of the core layer with QDs. The change of PL intensity for epi-wafer is good agreement with the behavior of the increased etching depth of the core layer which is evaluated by the measurements of scanning electron micrograph. We demonstrate a possibility of etching end-point detection and evaluation of etching rate during the dry etching of the core layer with QDs using in-situ optical emission spectroscopy.

Selectively transparent photonic crystals consisting of printed inorganic/organic hybrid dielectric films based on inorganic copper(I) thiocyanate can be produced to exhibit intense Bragg peaks over their stop band in the visible region. This work exhibits a unique approach to achieve the improvement of color purity and the strong directed emission pattern for polymer light-emitting diodes and AC-driven electroluminescent devices with printed inorganic/organic hybrid dielectric mirrors, which will be important for all-printed microlight sources.

The characteristics of organic photodetectors based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends with various film thicknesses of active layer are investigated. The red-shift in peak wavelength of incident-photon-to-current conversion efficiency (IPCE) spectra in the devices with various film thicknesses is observed with increasing film thickness. For thick devices upon irradiation by light with a photon energy of around energy gap of an active layer, excitons are formed almost uniformly because of the small absorption coefficient of red light. A conventional device with 2 μm-thick film exhibits narrow-band light detection with red-light sensitivity and the relatively narrow spectral response of the full-width at half-maximum (FWMH) of around 50 nm. On the other hand, an inverted device with 2 μm-thick film exhibits broadband light detection. For bulk heterostructure devices, one of important factors to realize the narrowband light detection is the control of charge carrier collection efficiency at electrodes which is attributed to the device structure, including the intrachain transport in polymer.

The internet of Things (IoT) is supported by various sensor and display devices. Microlight sources based on organic light-emitting transistors (OLETs) with an electrical switching capability, in which not only the position and extension of the emission area but also the emission color are controlled by gate voltage and drain voltage, are useful for augmented (AR) and virtual reality (VR) displays and sensor applications. OLETs with top gate architectures are advantageous as compared to bottom gate architectures due to easy of fabrication, low contact resistance and environmental stability. The fabrication of low-temperature processable, OH-group-free polymer gate dielectrics are also important for fabricating ambipolar OLETs. Poly(methyl methacrylate) (PMMA), which does not contain electron-trapping groups such as OH, is one of the promising candidate gate dielectrics in ambipolar OLETs. PMMA gate dielectric formed by using fluorine-based solvent (Asahi Glass AE-3000) is useful to prevent mixing of the dielectric layer with the emissive layer for the top-gated device fabrication. The device performance of top-gated OLETs based on a poly(p-phenylene vinylene) derivative, Super Yellow is improved owing to the fabrication without intermixing. A near-infrared emission from a phosphorescent dye, Pt-tetraphenyltetrabenzoporphyrin dopant is demonstrated.

The fabrication of inorganic/organic hybrid distributed Bragg reflector (DBR) is investigated to realize all-solution processed polymer light-emitting diodes (PLED s) with the narrowing of electroluminescence (EL) spectra. The large refractive index contrast between inorganic copper(l) thiocyanate, CuSCN and polymer, cellulose acetate results in the fabrication of DBR with high reflectivity (> 95 %) from nanostructures consisting of only five bilayers. The narrowing of EL spectrum with a full width at half maximum of approximately 25 nm is achieved from all-solution-processed PLED based on highly conductive poly(ethylenedioxythiophene):poly(styrenesulfonate) anode and super yellow as an emissive layer except for a silver cathode.

Direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric substrates, i.e., polymeric waveguide substrates to form flexile optical integrated devices is demonstrated. The OELD and OPD were fabricated by organic molecular beam deposition (OMBD) technique on a polymeric or a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signals of faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing diamine derivative, or rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives, as an emissive layer. Electrical signals are successively converted to optical signals for optical transmission of moving picture signals with OLED fabricated on a polymeric waveguide. OPDs utilizing phthalocyanines derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with the cutoff frequency of more than 5 MHz has been realized.

The properties of solution-processed top-gate-type n-channel organic field-effect transistors (OFETs) utilizing perylene dimide derivative films with silver (Ag) source/drain (S/D) electrodes are investigated. With an increase in the annealing temperature, the electron transport characteristics are improved. The increase in grain size leads to an increase in electron field-effect mobility. An OFET with Ag-nanowire (AgNW) S/D electrode fabricated on a polymer substrate exhibits n-channel characteristics with electron field-effect mobility of 0.04 cm 2 V -1 s -1 in air. We demonstrate the possibility of producing flexible and air-stable n-channel OFETs using AgNW electrodes.

Conducting polymers with highly extended /spl pi/-electron system in their main chains can be infiltrated into a nanoscale interconnected regular array of voids in synthetic opals either in solution or liquid states upon heating. Optical properties of opals and inverse opals such as transmission spectra and reflection spectra were found to change drastically upon infiltration of conducting polymer liquids or solutions. Amplified spontaneous emission, amplified resonant Raman line and multi-mode lasing were observed in opals infiltrated with conducting polymer solutions upon optical excitation.

The fabrication of organic light-emitting devices (OLEDs) by thermal printing method was demonstrated. The polarized electroluminescence of the fabricated OLEDs were obtained.

Organic photo-detectors (OPDs) have been discussed as high-speed photo-detectors, which consist of heterostructure of copper phthalocyanine (CuPc) and N,N'-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenedicarboximide (BPPC) layers. We analyzed the carrier transport in photodetectors, and the device has a cut-off frequency of more than 70 MHz. The imaging signals were successfully received using the OPD

Organic photo-detectors (OPDs) were examined as receivers for display systems. The cut-off frequency of more than 20 MHz bandwidth was obtained. The OPDs were demonstrated as a receiver of transmitting picture signals.

Polymer based efficient red light emission has been demonstrated utilizing red-emitting phosphor Ir(piq)/sub 3/ doped in mixture of PVK and TDAPB by spin coating method. The maximum luminance is obtained 8800 cd/m/sup 2/ and the external quantum efficiency of 6.3%. The impact test of the PLED shows a star like destruction of electrode by impact the EL device.

In this paper, we discussed fabrication and characteristics of layered polymeric OLED using water-soluble molecular and polymer with wet process for flexible display. We demonstrated the emission properties of OLEDs with the three-layered structure using water-soluble organic materials. The threshold voltage of an OLED with three-layered structure using water-soluble organic materials is lowered by 30% than that with two-layered structure.

Summary form only given. The OLEDs are fabricated on a glass substrate and a polymeric substrate. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate for an OLED of Alq/sub 3/ (8-hydroxyquinoline aluminum) as an emissive layer. Emission characteristics and pulse response characteristics of OLEDs are discussed. The pulse response of photo-detectors, consisting of multilayered phthalocyanines, shows that the cutoff frequency is drastically improved by decreasing the individual layer thickness and applying a reverse bias voltage.