While organic electronics is mostly dominated by light-emitting diodes, photovoltaic cells and transistors, optoelectronics properties peculiar to organic semiconductors make them interesting candidates for the development of innovative and disruptive applications also in the field of light signal detection. In fact, organic-based photoactive media combine effective light absorption in the region of the spectrum from ultraviolet to near-infrared with good photogeneration yield and low-temperature processability over large areas and on virtually every substrate, which might enable innovative optoelectronic systems to be targeted for instance in the field of imaging, optical communications or biomedical sensing. In this review, after a brief resume of photogeneration basics and of devices operation mechanisms, we offer a broad overview of recent progress in the field, focusing on photodiodes and phototransistors. As to the former device category, very interesting values for figures of merit such as photoconversion efficiency, speed and minimum detectable signal level have been attained, and even though the simultaneous optimization of all these relevant parameters is demonstrated in a limited number of papers, real applications are within reach for this technology, as it is testified by the increasing number of realizations going beyond the single-device level and tackling more complex optoelectronic systems. As to phototransistors, a more recent subject of study in the framework of organic electronics, despite a broad distribution in the reported performances, best photoresponsivities outperform amorphous silicon-based devices. This suggests that organic phototransistors have a large potential to be used in a variety of optoelectronic peculiar applications, such as a photo-sensor, opto-isolator, image sensor, optically controlled phase shifter, and opto-electronic switch and memory.

Organic light detectors: photodiodes and phototransistors.

This self-contained, comprehensive book describes the fundamental properties of soft x-rays and extreme ultraviolet (EUV) radiation and discusses their applications in a wide variety of fields, including EUV lithography for semiconductor chip manufacture and soft x-ray biomicroscopy. The author begins by presenting the relevant basic principles such as radiation and scattering, wave propagation, diffraction, and coherence. He then goes on to examine a broad range of phenomena and applications. The topics covered include EUV lithography, biomicroscopy, spectromicroscopy, EUV astronomy, synchrotron radiation, and soft x-ray lasers. He also provides a great deal of useful reference material such as electron binding energies, characteristic emission lines and photo-absorption cross-sections. The book will be of great interest to graduate students and researchers in engineering, physics, chemistry, and the life sciences. It will also appeal to practicing engineers involved in semiconductor fabrication and materials science.

X-Rays and Extreme Ultraviolet Radiation: Principles and Applications

X-ray sources such as free-electron lasers offer the potential to study matter at unprecedented spatial and temporal resolution. But that potential is limited by the poor quality of conventional X-ray optical elements. An in situ technique that corrects for wavefront aberrations and allows X-rays to be focused to a spot just 7 nm wide could provide a solution.

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Breaking the 10 nm barrier in hard-X-ray focusing

Relativistic high-power laser–matter interactions

Spectrally selective light detection is vital for full-colour and near-infrared (NIR) imaging and machine vision. This is not possible with traditional broadband-absorbing inorganic semiconductors without input filtering, and is yet to be achieved for narrowband absorbing organic semiconductors. We demonstrate the first sub-100 nm full-width-at-half-maximum visible-blind red and NIR photodetectors with state-of-the-art performance across critical response metrics. These devices are based on organic photodiodes with optically thick junctions. Paradoxically, we use broadband-absorbing organic semiconductors and utilize the electro-optical properties of the junction to create the narrowest NIR-band photoresponses yet demonstrated. In this context, these photodiodes outperform the encumbent technology (input filtered inorganic semiconductor diodes) and emerging technologies such as narrow absorber organic semiconductors or quantum nanocrystals. The design concept allows for response tuning and is generic for other spectral windows. Furthermore, it is material-agnostic and applicable to other disordered and polycrystalline semiconductors.

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Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes

Organic electroluminescent diodes (OLED) were fabricated on a polymeric optical waveguide for use as an optical interconnector in data communication systems. The OLED were fabricated on an ITO sputtered polymer waveguide with a 45 degree mirror by vacuum deposition. The OLEDs, with an emission peak center at 520 nm consist of diamine derivative as a hole transporting layer and tris(8-hydroxyquinoline) aluminum (Alq3) as an emissive layer. We estimated the propagation losses of the waveguide to be 1.35 dB/cm at 520 nm. However, it decreases as increasing the wavelength of the light source and is estimated as 0.37 dB/cm at the wavelength of 614 nm. The optical pulse of more than 5 Mb/s has been obtained from the OLED with Alq3 and diamine derivative. We discuss the properties of the OLED for the light source for polymeric integrated devices.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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Organic electroluminescent diodes as a light source for polymeric integrated devices

A microfocusing experiment for hard X-rays has been performed to evaluate the performance of Fresnel zone plate optics. A tantalum Fresnel zone plate with an outermost zone width of 50 nm and a thickness of 0.5 µm has been fabricated by electron-beam lithography. The focused beam size measured by a knife-edge scan is 58 nm in full-width at half-maximum for the first-order diffraction at an X-ray energy of 8 keV. It can be concluded that this zone plate has nearly diffraction-limited resolution in the hard X-ray region. The measured diffraction efficiency is 5% at 8 keV. The spot size using the third-order focus of the zone plate is measured to be approximately 30 nm.

https://iopscience.iop.org/article/10.1143/JJAP.44.1994/pdf

Performance Test of Fresnel Zone Plate with 50 nm Outermost Zone Width in Hard X-ray Region

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.

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Realization of polymeric optical integrated devices utilizing organic light-emitting diodes and photodetectors fabricated on a polymeric waveguide

We present an electron beam nanolithography system which features sub-10-nm beam size over a large 480×480 µ m2 field and a high 70 kV acceleration voltage with a Zr/O/W thermal field emitter tip. A beam can be deflected at 100 MHz in 2-nm steps, which allows the use of highly sensitive resist. The system is equipped with a highly sensitive YAG detector for electrons backscattered from a registration mark as well as a C/W multilayer knife edge for beam size measurement and focusing. These techniques achieve a beam size of about 6 nm. A 10-nm-scale resist pattern was obtained using ZEP520 resist with this system. Furthermore, Si nanostructures have been obtained by using an image reversal process with ECR plasma oxidation. Photoluminescence was observed from the Si nanowires fabricated with this system.

An Electron Beam Nanolithography System and its Application to Si Nanofabrication

Multi-layered flyer (aluminum–polyimide–tantalum) is designed as a high speed flyer making use of shock impedance matching and reverberation techniques. The designed three layered targets have been irradiated using a 20 J laser beam. Flyer velocities are measured by observing the flyer impact emissions on glass step targets within a 500 μm laser focal spot at laser intensities 5×1012–2×1013 W/cm2. Thin (0.5–1.0 μm) Ta layers of the flyers are accelerated via shock reverberations between the thick polyimide and thin Ta layers for the first time using laser induced shock waves. Their velocities are measured to be more than 13 km/s with a good hydrodynamic stability. The obtained velocity is faster than the ones obtained by a conventional flyer method such as a double gas gun.

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Hisataka Takenaka

Papers

Organic electroluminescent diodes as a light source for polymeric integrated devices

Performance Test of Fresnel Zone Plate with 50 nm Outermost Zone Width in Hard X-ray Region

Realization of polymeric optical integrated devices utilizing organic light-emitting diodes and photodetectors fabricated on a polymeric waveguide

An Electron Beam Nanolithography System and its Application to Si Nanofabrication

Multi-layered flyer accelerated by laser induced shock waves