Huipeng Chen

Effects of Nitrogen and Hydrogen Codoping on the Electrical Performance and Reliability of InGaZnO Thin-Film Transistors

Despite intensive research on improvement in electrical performances of ZnO-based thin-film transistors (TFTs), the instability issues have limited their applications for complementary electronics. Herein, we have investigated the effect of nitrogen and hydrogen (N/H) codoping on the electrical performance and reliability of amorphous InGaZnO (α-IGZO) TFTs. The performance and bias stress stability of α-IGZO device were simultaneously improved by N/H plasma treatment with a high field-effect mobility of 45.3 cm2/(V s) and small shifts of threshold voltage (Vth). On the basis of X-ray photoelectron spectroscopy analysis, the improved electrical performances of α-IGZO TFT should be attributed to the appropriate amount of N/H codoping, which could not only control the Vth and carrier concentration efficiently, but also passivate the defects such as oxygen vacancy due to the formation of stable Zn-N and N-H bonds. Meanwhile, low-frequency noise analysis indicates that the average trap density near the α-IGZO/SiO2 interface is reduced by the nitrogen and hydrogen plasma treatment. This method could provide a step toward the development of α-IGZO TFTs for potential applications in next-generation high-definition optoelectronic displays.

Solution-Processed Organic Thin-Film Transistor Arrays with the Assistance of Laser Ablation

A key step toward commercialization of organic thin-film transistors (OTFTs) is to manufacture large-area OTFT arrays with desired uniform device performance. In this work, for the first time, solution-processed OTFT arrays were fabricated with the assistance of laser ablation. The source-drain electrodes and the whole devices were patterned by precise control of laser intensity and process path. Compared with traditional methods, this approach significantly simplifies the fabrication process of OTFT arrays with high quality and high yield. A careful selection of laser processing parameters is key to obtaining high quality and high performance OTFT arrays. The grazing incidence X-ray diffraction experiments and device performance tests ensured the selection of proper laser ablation intensity. Eventually, the OTFT arrays on silicon wafer and ITO glass exhibited uniform electrical characteristics with the mean mobility of 0.16 and 0.10 cm2 V-1 s-1, respectively. These results demonstrated that the laser ablation process provides a promising tool to simplify the fabrication of solution-processed OTFT arrays with low cost and high yield, which has great potential in upscaling of high performance OTFT arrays for display and circuits.

Solution-processed metal oxide arrays using femtosecond laser ablation and annealing for thin-film transistors

In this study, a femtosecond (fs) laser is proposed to pattern and anneal a metal oxide active layer for the facile fabrication of metal oxide thin-film transistor (TFT) arrays. Compared with conventional photolithography and lift-off techniques, fs-laser ablation significantly simplified the patterning process due to its advantages such as no contact, high yield and high resolution. Uniform patterned arrays with sharp edges and small feature size (down to 32 μm) were achieved using fs-laser ablation. Moreover, fs-laser annealing was also applied for rapid conversion of the precursor to metal oxide lattices. The results showed that an increase in laser intensity lead to an improvement in charge carrier mobility and an improvement in the on–off current ratio of indium zinc oxide (IZO) thin film transistors (TFTs) along with a negative shift of the threshold voltage. X-ray photoelectron spectroscopy (XPS) analysis indicates that an increase in laser intensity enhanced the breakdown of weak or metastable chemical bonds within IZO films, leading to the removal of hydroxide-related (OH) species and enhancement of metal oxide composition and oxygen vacancies (Ov); it facilitated carrier transport and led to an average mobility up to 9.0 cm2 V−1 s−1. Furthermore, compared with thermal annealing (TA), fs-laser annealing could reduce the thermal budget and more effectively realize the dehydroxylation behavior for OH-related species, resulting in higher charge mobility. These results clearly demonstrated that fs-laser ablation and annealing could provide a promising tool to significantly simplify the fabrication of metal oxide TFT arrays due to their advantages such as high resolution, high yield and low cost. Hence, these techniques show great potential to be applicable in the fabrication of large-area metal oxide TFT arrays for use in display devices and circuits.

High-Performance Nonvolatile Organic Transistor Memory Using Quantum Dots-Based Floating Gate

A novel nonvolatile floating-gate transistor memory device using CdSe@ZnS quantum dots (QDs) embedded the insulating polymer as a charge-storage layer along with the rational design of device structure is presented. The core–shell structure CdSe@ZnS QDs can efficiently trap both holes and electrons under the applied writing/erasing operations, resulting in a considerable threshold voltage shifts (<inline-formula> <tex-math notation=LaTeX>

Modulation of bulk heterojunction morphology through small π-bridge changes for polymer solar cells with enhanced performance

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High performance inkjet-printed metal oxide thin film transistors via addition of insulating polymer with proper molecular weight

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Inkjet-Printed Vertical Organic Field-Effect Transistor Arrays and Their Image Sensors

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Importance of Solvent Removal Rate on the Morphology and Device Performance of Organic Photovoltaics with Solvent Annealing

</tex-math></inline-formula> can maintain 76% at 10⁸ s) and outstanding endurance characteristics (>500 cycles), demonstrating extraordinary stable and reliable memory property. Moreover, a thin layer of Al₂O₃ was introduced as tunneling dielectric layer which is essential for the high-performance floating-gate transistor memory device. The nonvolatile organic transistor memory devices using QDs-based floating gate show great potential application for high-performance organic memory devices.

Importance of domain purity in semi‐conducting polymer/insulating polymer blends transistors

Investigations on the relationships among the chemical structures, morphology and photovoltaic properties of conjugated polymers are crucial in designing high-efficiency semiconducting polymers. Here, two novel copolymers, PIBTO-T and PIBTO-TT, were designed and synthesized to demonstrate the improvement in photovoltaic performance of conjugated polymers by a small change in their chemical structures. PIBTO-TT with thieno[3,2-b]thiophene π-bridges has a more linear backbone conformation, thereby resulting in enhanced intermolecular π–π interactions compared to PIBTO-T with thiophene π-bridges. Benefiting from the closer intermolecular π–π stacking, PIBTO-TT:PC71BM exhibits a higher hole mobility than PIBTO-T:PC71BM. Morphological studies reveal that the miscibility of PC71BM in PIBTO-TT is better than that in PIBTO-T. This enhanced miscibility could shorten the distances between adjacent fullerenes and improve electron transportation in the miscible region. Meanwhile, PIBTO-TT:PC71BM blends have larger donor/acceptor interfacial areas than PIBTO-T:PC71BM samples. All these factors contribute to the better photovoltaic performance of PIBTO-TT-based devices. This study clearly shows that the morphological characteristics and photovoltaic properties of conjugated polymers are closely related to their molecular structures, and the manipulation of backbone conformation through π-bridge modulation is a promising molecular engineering approach to improve the photovoltaic properties of conjugated polymers.

Improving Charge Mobility of Polymer Transistors by Judicious Choice of the Molecular Weight of Insulating Polymer Additive

Fabrication of metal oxide thin film transistor (MOTFT) arrays using the inkjet printing process has caused tremendous interest for low-cost and large-area flexible electronic devices. However, the inkjet-printed MOTFT arrays usually exhibited a non-uniform geometry due to the coffee ring effect, which restricted their commercial application. Therefore, in this work, a strategy is reported to control the geometry and enhance device performance of inkjet-printed MOTFT arrays by the addition of an insulating polymer to the precursor solution prior to film deposition. Moreover, the impact of the polymer molecular weight (MW) on the geometry, chemical constitution, crystallization, and MOTFT properties of inkjet-printed metal oxide depositions was investigated. The results demonstrated that with an increase of MW of polystyrene (PS) from 2000 to 200u2009000, the coffee ring was gradually faded and the coffee ring effect was completely eliminated when MW reached 200u2009000, which is associated with the enhanced visco...