Flexible field-effect transistors from a liquid crystalline semiconductor by solution processes

The fabrication of organic semiconductor thin films by printing technologies is expected to enable the low-cost production of devices such as flexible display drivers, RF-ID tags, and various chemical/biological sensors. However, large-scale high-speed fabrication of uniform semiconductor thin films with adequate electrical properties for these devices remains a big challenge. Herein, we demonstrate an ultrafast and scalable fabrication of uniform polycrystalline thin films with 100% surface coverage using liquid crystalline semiconductors such as 2-phenyl-7-decyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) and 2.7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8), at a rate of 3 orders of magnitude higher than before, i.e., 40 mm/s (2.4 m/min) or more by dip-coating in the drainage regime. Organic transistors fabricated with polycrystalline thin films of Ph-BTBT-10 show average mobilities of 4.13 ± 0.75 cm2/(V s) in the bottom-gate-bottom-contact configuration and 10.90 ± 2.40 cm2/(V s) in the bottom-gate-top-contact configuration comparable to those of the devices prepared with single-crystalline thin films. More importantly, these films almost maintain the FET performance when the substrate size is extended up to 4 square inch. The present findings are available for other liquid crystalline semiconductors and bring us one step closer to the realization of printed electronics.

In this work, a solution processed Al-In-O/InOx bilayer resistive switching random access memory (RRAM) is demonstrated at temperature as low as 180 °C. The memory cell exhibits remarkable forming free resistive switching characteristics with stable data retention and low set/reset voltages. More importantly, this solution processed bilayer shows stable memory properties under different bending angles on a flexible substrate. The resistive switching mechanism was systematically investigated. Compared to single layer devices, an Al-In-O mixing layer is induced by the solution process in the bilayer RRAM. The first principle calculation confirms that in the Al-In-O mixing layer, the formation energy of oxygen vacancies is significantly reduced compared with the AlOx layer. As a result, the formation of the oxygen vacancy based conductive filament is realized without the electroforming process. The RRAM fabricated by the printable solution process at low temperature shows great application potential in next generation wearable electronics.

Pristine fullerenes mixed by vacuum-free solution process: Efficient electron transport layer for planar perovskite solar cells

A flexible polymer field effect transistor with a nanoscale carbon nanotube channel is conceptualized and realized herein. Carbon nanotubes (CNTs) were dispersed on a polyimide substrate and marked in an scanning electron microscope with focused ion beam such that they could be contacted with gold nanoink. The CNTs were divided into two parts forming the source and drain of the transistor. A micropipette writing method was used to contact the carbon nanotube electrodes with gold nanoink and to deposit the poly(3-hexylthiophene) as an active layer. The mobility of the transistors is of the order of 10−5cm∕Vs. After fabrication, the flexible transistors can be peeled off the substrate.

Dual-functional ultrathin wearable 3D particle-in-cavity SF-AAO-Au SERS sensors for effective sweat glucose and lab-on-glove pesticide detection

Organic light-emitting diodes (OLEDs) based on vacuum deposited small molecules have undergone significant progress since the first efficient double-layered OLEDs were reported in 1987 by Tang and Van Slyke. Recently, solution processed small molecular OLEDs are also drawing more and more research attention, as such a technology combines advantages of the facile synthesis of small molecules and the low-cost solution process like polymers. The performance of OLEDs made by solution process is gradually catching up with their vacuum deposited counterparts. This feature article will review the device structures adopted to achieve high performance solution processed OLEDs, the development of solution processable small molecules, and the comparisons of the different nature of the films and devices fabricated by solution-process or by vacuum deposition. Finally, the prospects and remaining problems will be discussed.

PSS) on nanostructures. Here we demonstrate low-pressure-assisted coating method of PSS on surface-modified silicon nanotips with broadband light-trapping characteristics to improve interface property and to achieve high-efficiency hybrid solar cells through a solution process. The approach enhances the effective minority-carrier lifetime and the coverage of PSS on the surface of nanostructures. Hybrid solar cells fabricated with surface-modified nanotips exhibit a high fill factor of 70.94%, short-circuit current density of 35.36 mA/cm(2), open-circuit voltage of 0.528 V, and power conversion efficiency of 13.36%. The high efficiency and the high fill factor are achieved because of conformal coating of PSS via a low-pressure-assisted coating process, excellent light harvesting without sacrificing the minority-carrier lifetime, and efficient charge separation/collection of photogenerated carriers.

The polarization state can encode far more information compared to the intensity and spectrum of light signals. Polarization imaging and determination of polarization state has been a fascination of researchers in the field of optical engineering. Conventional polarization imaging involves complex methods and expensive manufacturing processes. Additionally, in recent times easily fabricate able semiconductor devices such as solution processed quantum dot (QD) LEDs 16 , quantum rod (QR) LEDs 13 ‐ 15 , QD photodetectors (PDs), etc. have gained tremendous interest and research efforts. The ability to fabricate a solution processable polarization detector can prove to be pivotal in the pursuit of facile polarization detection. Traditional polarization imaging systems make use of expensive wire‐grid polarizers and complicated patterning processes that make it challenging to realize such devices, the resulting devices are also quite expensive which limits their widespread application. In this work we present a novel system that makes use of a completely solution process fabricated QD PD using lead sulfide (PbS) QDs that can detect the whole visible spectrum and integrate a solution processable Azo‐dye polarizer (AD1) onto it to achieve patterned polarized detection. The PD achieved a response time of around 30 fis and the AD1 polarizer achieved a maximum extinction ratio of ~27:1. The fabricated AD1 polarizer also covers wavelengths in the range of 450 nm to 750 nm making it ideal for the visible spectrum The work represents a significant step forward in a facile and cheap polarized detector fabrication method that can enable a wider adoption of polarization imaging. Further optimization in pixelization and device architecture is expected to lead to a widespread implementation of such technology.

Graphical differentiation substantially promotes the understanding of basic concepts of calculus. At the same time, such tasks are challenging for many students. To be able to support students in complex tasks during the solution process, it is important to recognise if students are having difficulties and, if so, to identify precisely what the difficulty is. However, previous research was only able to identify correct and incorrect solution processes but not the specific difficulties of students. In our study, the eye tracking data of 143 students reveal how students’ math tasks in context of graphically differentiation can be predicted. Retrospective-think-aloud (RTA) protocols were used to identify students’ difficulties and three machine learning algorithms, k-nearest neighbours (KNN), Random Forest and support vector machine (SVM), provide an accurate prediction for this multiclass problem. The prediction results improve with increasing processing time and achieve already good values long before the solution process of the tasks is completed. Our results show that certain student difficulties can be detected very early during the task solution process. Although this approach has been demonstrated for a sub-area of calculus, it is transferable to other fields of the STEM domain and therefore has much wider scope.

Solution processes have promising advantages of low manufacturing cost and large-scale production, potentially applied for the fabrication of organic and quantum dot light-emitting diodes (OLEDs and QLEDs). To meet the expected lifespan of OLEDs/QLEDs in practical display and lighting applications, tandem architecture by connecting multiple light-emitting units (LEUs) through a feasible intermediate connection layer (ICL) is preferred. However, the combination of tandem architecture with solution processes is still limited by the choices of obtainable ICLs due to the unsettled challenges, such as orthogonal solubility, surface wettability, interfacial corrosion, and charge injection. This review focuses on the recent progresses of solution-processed tandem OLEDs and tandem QLEDs, covers the design and fabrication of various ICLs by solution process, and provides suggestions on the future challenges of corresponding materials and devices, which are anticipated to stimulate the exploitation of the emerging light technologies.

High flexibility and solution processability have made all polymer organic phototransistors (AP-OPTs) a suitable candidate for various wearable and smart home applications. However, fabrication of the AP-OPTs via the solution process is still challenging owing to the possible degradation of the polymer gate dielectric layer by the solvent of the organic semiconductor, resulting in hampered device performance. To circumvent this issue, the unidirectional floating film transfer method (UFTM), having the least impact on the underlying organic dielectric film, has been used to obtain highly oriented P3HT thin film. Further, the effect of P3HT film orientation with respect to the channel has been investigated. Results revealed that the device with parallel orientation performed better with Photosensitivity of 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and Photoresponsivity of 133 A/W.

With the development of wearable devices and hafnium-based ferroelectrics (FE), there is an increasing demand for high-performance flexible ferroelectric memories. However, developing ferroelectric memories that simultaneously exhibit good flexibility and significant performance has proven challenging. Here, we developed a high-performance flexible field-effect transistor (FeFET) device with a thermal budget of less than 400 °C by integrating Zr-doped HfO2 (HZO) and ultra-thin indium tin oxide (ITO). The proposed FeFET has a large memory window (MW) of 2.78 V, a high current on/off ratio (ION/IOFF) of over 108, and high endurance up to 2×107 cycles. In addition, the FeFETs under different bending conditions exhibit excellent neuromorphic properties. The device exhibits excellent bending reliability over 5×105 pulse cycles at a bending radius of 5 mm. The efficient integration of hafnium-based ferroelectric materials with promising ultrathin channel materials (ITO) offers unique opportunities to enable high-performance back-end-of-line (BEOL) compatible wearable FeFETs for edge intelligence applications.

In this paper, a blue fluorescent organic light-emitting diode (OLED) with a 1 cm2 emitting area was fabricated by a solution process. The ITO/spin MADN:13% UBD-07/TPBi/Al was used as the basic structure in which to add a hole-injection layer PEDOT:PSS and an electron-injection layer LiF, respectively. The device structure was optimized to obtain a longer lifetime. Firstly, the TPBi, which is an electron transport layer and a hole-blocking layer, was added to the structure to increase the electron transport rate. When the TPBi thickness was increased to 20 nm, the luminance was 221 cd/m2, and the efficiency was 0.52 cd/A at a voltage of 8 V. Since the addition of the hole-injection layer (HIL) increased the hole current but did not increase the electron current, the electron transport layer (ETL) Alq3 with the lowest unoccupied molecular orbital (LUMO) was added as stepped ETL to help the TPBi transport more electron current into the emitting layer. When the thickness of the TPBi/Alq3 was 10 nm/15 nm, the luminance reached 862 cd/m2, the efficiency was 1.29 cd/A, and the lifetime increased to 252 min. Subsequently, a hole-injection layer PEDOT:PSS with a thickness of 55 nm was added to make the ITO surface flatter and to reduce the probability of a short circuit caused by the spike effect. At this time, the luminance of 311 cd/m2, the efficiency of 0.64 cd/A, and the lifetime of 121 min were obtained. Following this, the thickness of the emitting layer was doubled to increase the recombination probability of the electrons and the holes. When the thickness of the emitting layer was 90 nm, and the thermal evaporation method was used, the efficiency was 3.23 cd/A at a voltage of 8V, and the lifetime was improved to 482 min. Furthermore, when the thickness of the hole-injection layer PEDOT:PSS was increased to 220 nm, the efficiency increased to 3.86 cd/A, and the lifetime was increased to 529 min. An infrared thermal image camera was employed to detect the temperature variation of the blue OLEDs. After the current was gradually increased, it was found that the heat accumulation of the device became more and more significant. When the driving current reached 50 mA, the device burnt out. It was found that the maximum temperature that the OLED device could withstand was approximately 58.83 degrees C at a current of 36.36 mA.

A transparent, flexible graphene field effect transistor (GFET) based on ferroelectric gate is demonstrated. In this device, the single layer graphene was fabricated by chemical vapor deposition method, and transferred to the polyethylene terephthalate substrate. Then the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric polymer layer film was used as the gate dielectric for the graphene FET. Based on the P(VDF-TrFE)/graphene heterojunction FET, Hall Bar structure was fabricated. The transport properties of the graphene channel at low temperature and retention characteristics at different temperature are investigated in detail. These special properties indicated that the GFET might be useful for many particular applications, such as a non-volatile memories, flexible electronic devices and phototransistors.

In this study, the ability of mathematical reasoning is measured based on its indicators, namely, drawing logical conclusions, providing explanations with models, facts, characteristics or relationships, estimating answers and solution processes and formulating valid arguments. This type of research is qualitative research using a descriptive approach. The research was conducted at MTs Negeri 5 Merangin. The subjects used in this study were 3 students who were taken from class VII-B.The results showed that students who have mathematical reasoning abilities SKP-01 have been able to meet all indicators of mathematical reasoning abilities. SKP-02 students with mathematical reasoning abilities are unable to meet the indicators of compiling valid arguments. And SKP-03 students are not able to meet the indicators of estimating the answer and the solution process and the indicators compile valid arguments. So the three subjects who have different mathematical reasoning abilities, have obstacles in fulfilling different mathematical ability indicators.Thus, efforts to improve children's abilities in learning mathematics, especially in their mathematical reasoning abilities, require the selection of appropriate learning methods, encouraging students to interact positively with fellow students and with teachers when learning, encouraging students to use logical reasoning in solving math problems.