KEYWORDS: Photovoltaics, Electrodes, Absorption, Gold, Polarization, Organic photovoltaics, Thin film devices, Thin film solar cells, Anisotropy, Thin films
We report the fabrication of polarization-sensitive photovoltaic devices made of hetero-junction type vacuum-sublimed multilayer films composed of aligned 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (aligned-PTCBI) and titanyl phthalocyanine (TiOPc). The PTCBI layer was successfully made to be well aligned without losing high photovoltaic power-conversion efficiency. High polarization sensitivity was achieved at around 540 nm. The device configuration was ITO/In/aligned-PTCBI/TiOPc/PEDOT:PSS/Au and the thickness of each layer was optimized for polarization-sensitive photo-detection. The power-conversion efficiencies under the polarized white light parallel and perpendicular to the molecular-orientation axis, through the ITO electrode were 0.78% and 0.45%, respectively. The ratio of short-circuit current, parallel to perpendicular, was 1.66. This device can be used as transparent photo-detectors, because the transmittance of the Au electrode was about 40% at 500-600nm. The short-circuit current ratio was increased to 3.0, when 510nm monochromatic polarized light through the Au electrode was used.
High field-effect hole mobility of (formula available in paper)and threshold voltage is -3.2 V) in organic-inorganic layered perovskite film (formula available in paper)prepared by a vapor phase deposition technique have been demonstrated through the octadecyltrichlorosilane treatment of substrate. Previously, the (formula available in paper)films prepared on the
octadecyltrichlorosilane-covered substrates using a vapor evaporation showed not only intense exciton absorption and photoluminescence in the optical spectroscopy but also excellent crystallinity and large grain structure in X-ray and atomic force microscopic studies. Especially, the (formula available in paper)structure in the region below few nm closed to the surface of octadecyltrichlorosilane monolayer was drastically improved in comparison with that on the non-covered substrate. Though our initial (formula available in paper)films via a same sequence of preparation of (formula available in paper)and octadecyltrichlorosilane monolayer did
not show the field-effect properties because of a lack of spectral, structural, and morphological features. The unformation of favorable
(formula available in paper)structure in the very thin region, that is very important for the field-effect transistors to transport electrons or holes, closed to the surface of non-covered (formula available in paper)dielectric layer was also one of the problems for no observation of them. By adding further optimization and development, such as deposition rate of perovskite, substrate heating during deposition, and tuning device architecture, with hydrophobic treatment, the vacuum-deposited (formula available in paper)have achieved above-described high
performance in organic-inorganic hybrid transistors.
A flexible insulator film would be one of the most important elements of flexible organic field-effect transistors (OFETs). It should be produced from a soft organic material rather than a stiff inorganic material. Many polymeric materials were spin-coated from the solution and the resulted films have to be baked or cured to obtain a good insulator. Since those procedures impose a restriction on the OFETs, a fabrication process without using a solvent has been desired. Poly-p-xylylene derivatives have been made into an insulator film by a non-solvent procedure, chemical vapor deposition (CVD). The insulator film has additional advantages, pinhole-free, resistance to many solvents and no thermal stress to a material beneath. We have fabricated and characterized OFETs with the inverted staggered geometry, substrate/ gate electrode/ poly-p-xylylene derivatives/ organic semiconductor/ source-drain electrodes. And the CVD enables to form an insulator film even above the organic semiconductor. So we fabricated the staggered type configuration, substrate/ source-drain electrodes/ organic semiconductor/ poly-chloro-p-xylylene/ gate electrode. The device performance of a staggered type transistor indicated that the molecular arrangement of organic semiconductor at the insulator interface is more dominant than the damage or chemical deterioration due to the attack of the radicals during the CVD procedure.
Thin buffer layers composed of tris(8-quinolato) aluminum (Alq) layer doped with Li-acetylacetonate (Li-acac), Mg-acac and magnesium metal were inserted between an MgAg cathode and an Alq electron transport layer in standard double-layer devices with the ITO/TPD/Alq/MgAg structure. The insertion of the buffer layers with Li-acac brought about large decrease in drive voltage. While the effects of Mg-acac and magnesium metal were smaller than the case of Li-acac. Electron drift mobility of Alq layers doped with Li-acac and magnesium metal was evaluated by using a time-of-flight method. Large increases of electron mobility as well as the increase of dark conductivity with doping were found.
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