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Ferromagnetic semiconductors with structural flexibility are an indispensable feature for future flexible spin-electronic applications. In this case, we introduce magnetic ingredients into an organic semiconductor, namely, pentacene, to form a ferromagnetic organic semiconductor (FOS). The first observation for ferromagnetic Ni-doped pentacene semiconductors at room temperature in the field of semiconductor spintronics is reported in this article. To date, the mechanism of FOSs with ferromagnetism is not understood yet, especially when their Curie temperature is enhanced above room temperature. Here, we demonstrate dopants of Ni atoms and the modulation of the growth temperature in the FOS films to achieve room-temperature ferromagnetic properties in a series of FOS films, one of which has a maximum coercivity of 257.6 Oe. The spin-exchange interaction between a Ni atom and a pentacene molecule is detected through the magnetic hysteresis obtained using a superconducting quantum interference device magnetometer. We verify the effectiveness of this spin coupling through magnetic force microscopy, Raman spectroscopy, scanning Kelvin probe microscopy, and theoretical simulation. A model for the indirect spin coupling between Ni atoms is proposed for the mechanism of room-temperature ferromagnetic ordering of spins due to the exchange force indirectly. We believe that the π-electrons of pentacene molecules at the triple state for this model can support the spin coupling of electrons of Ni atoms. Our findings facilitate the development of brand-new spintronic devices with structural flexibility and room-temperature ferromagnetism.

The economic growth in many parts of the world during the past decade was sustainable because of affordable energy prices. The dependence on oil and electricity has made energy a vital component of our energy needs. In the 20th century, the populationquadrupled, and our energy demand increased by 16 times. The exponential energy demand is exhaust ing our fossil fuel supply at an alarming rate. About 13 terawatts (TW) of energy is currently needed to sustain the lifestyle of 6.5 billion people worldwide. By the year 2050, we will need an additional 10 TW of clean energy to maintain the current lifestyle [1]. To achieve this goal, alternative energy sources to coal,oil, and gas must be provided, such as power from wind and water, biomass, or solar energy. While a future energy mix will most likely be based on all of these sources, only the sun provides the earth with about 104-times more energy than the global daily consumption. Solar energy can be converted to different kinds of energies, such as heat, hydrogen, and electricity. The most direct way is to convert sunlight into electricity by solar cells [2].

In this study, TiO 2 nanorods arrays (TiO 2 NRAs) were synthesized by hydrothermal method. The maxima current density and conversion efficiency were 2.5 mA/cm 2 at 1.23 V vs. RHE and 0.95% with length of 6-7 μm under AM 1.5G 1sun condition. To improve the conversion efficiencies, Cu 2 ZnSnS 4 (CZTS), which owns direct band gap semiconductor with 1.5 eV and suitable band positions, was employed to extend the absorption range. In this study, CZTS nanoparticles were decorated on TiO 2 NRAs with adhesion layer by using solvothermal method. Finally, ZnS layer was used as passivation layer for increasing conversion efficient. By using ZnS as passivation layer, the current density increased from 2.92 mA/cm 2 to 6.91 mA/cm 2 and the conversion efficiency increased from 1.44% to 3.50%. According to electrochemical impedance spectroscopy (EIS) analysis, the result showed that the ZnS layer could reduce the electron-hole recombination loss to improve the conversion efficiency.

The development of low voltage-operating organic thin-film transistors requires high-dielectric constant (high-K) materials for the device's gate dielectrics. The surface properties of these high-K materials must match those of organic semiconductors. A modification material coated on high-K dielectric is needed, and polyimide (PI) is a promising modifier to reduce the surface energy and the interface trap states (in the level of 1010 cm−2 eV−1) of the high-K dielectrics. In this study, surface characteristics of the dielectrics were identified and interface analyses at the dielectric/organic semiconductor interface were conducted through combined electrical force microscopy and impedance–admittance investigation. When the organic semiconductor pentacene was grown on the PI-modified dielectrics, the atomic force microscopy images and X-ray diffraction analyses showed larger grain size and higher crystallinity than those on native high-K dielectrics. Using polyimide-modified high-K materials as the gate dielectric, high performances (SS 105) and low voltage-operating (

Cascade CdS/CdSe/ZnS quantum dots sensitized titanium dioxide nanorod arrays (TiO2–NRAs) solar cells exhibiting a high efficiency of around 3.06% have been obtained. Under AM 1.5, 100 mW cm−2 illumination, a short-circuit current density of 13.83 mA cm−2 and an open-circuit voltage of 0.45 V are obtained. This efficiency is relatively higher than other QDs-sensitized TiO2 NRAs solar cells previously reported in the literature.

Polymorphism control of organic semiconductor films greatly affects optoelectronic device performance. The thin-film phase is always the dominant phase in the early growth of pentacene films; however, the performance of the bulk phase is superior to that of the thin-film phase. In the present study, a nanoimprinted polyimide layer is used to induce the growth of the bulk phase in the early stage. The bulk phase appears in the initial few layers and its dominance of the polymorphisms in the pentacene film increases with increasing thickness. The mechanism of the phase transformation is explained.

We demonstrate a plasma-beam-processed polyimide (PI) surface to effectively align liquid crystal (LC) molecules. The pretilt angles of LCs can be varied between 0 and 3.5°, and the PI surface energy can be adjusted by controlling the plasma beam with an energy of 450 eV at an incident angle varying from 0 to 80° with respect to the normal direction of the substrate. Additionally, a method was developed to quickly evaluate the level of anchoring force of LC when compared with a rubbed-aligned LC cell. The performance of this method should be under LC cells with the same alignment materials.

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