In this letter, low-voltage operation and high mobility are simultaneously achieved in the OTFTs based on an elaborately constructed tri-layer gate dielectric. The tri-layer gate dielectric consists ...of the cross-linked poly(4-vinylphenol) (CL-PVP), polyvinylpyrrolidone (PVPy) and poly(styrene) (PS) films. The ultrathin CL-PVP and PS films prevent the charges transferring and trapping in the PVPy dielectric, which improves the performances. The low trap density at the organic semiconductor/dielectric interface contributes to the low-voltage operation and high mobility in the OTFTs. The OTFTs exhibit promising performances with high mobility exceeding 10 cm 2 /vs, small subthreshold swing of 185 mV/decade on average, high on/off ratio of <inline-formula> <tex-math notation="LaTeX">10^{{5}} </tex-math></inline-formula>, at low operating voltages below 5 V. The measurements on stability and ageing of the OTFTs indicate that the encapsulation is required for practical application.
Crystalline or amorphous metal oxides are widely used in various optoelectronic devices as key components, such as transparent conductive electrodes, dielectrics or semiconducting active layers for ...thin‐film transistor (TFT) backplanes in large‐area displays, photovoltaics, and light‐emitting diodes. Although crystalline inorganic materials demonstrate outstanding optoelectronic performance, owing to their wide bandgaps, large conductivities, and high carrier mobilities, their inherent brittleness makes them vulnerable to mechanical stress, thereby limiting the use of metal‐oxide films in emerging flexible electronic applications. In this study, stress‐diffusive organic–inorganic hybrid superlattice nanostructures are developed to overcome the mechanical limitation of crystalline oxides and to provide high mechanical stability to metal‐oxide semiconductors. In particular, hybrid transparent superlattice electrodes based on crystalline indium–tin oxide exhibit high electrical conductivities of up to 555 S cm–1 (resistance variation < 3%) and effectively reduce the mechanical stress on the inorganic layer (up to 10 000 bending cycles with a radius of 1 mm). Furthermore, to ensure the viability of the hybrid superlattice flexible electronics, all solution‐processed superlattice crystalline indium–gallium‐oxide TFTs are implemented on a thin (≈5 µm) polyimide substrate, providing highly robust and excellent electrical performance (average mobility of 7.6 cm2 V–1 s–1).
A facile, high‐throughput, solution‐processed industrial standard metal‐oxide material is fabricated for flexible optoelectronic devices. The huge demand for flexible electronic devices needs a new class of materials. Instead of spending time on not well‐studied materials, the solution‐processed hybrid superlattice with industrial standard metal‐oxide and organic materials can be successfully applied in flexible electronic devices.
The disordered chain arrangement of polymer dielectrics has complex both internal and external effects on system performance, which generally stimulates the weak acquisition and grain boundaries of ...vapor‐deposited organic small molecule films (VDOSMFs) with thermally activated charge transport. As a result, achieving “band‐like” transmission of VDOSMs on polymer dielectrics is attempting to prove to be a major challenge. Three types of bi‐polymer dielectrics are developed to modulate charge transport from thermally activated mode to “band‐like” transport at the interfacial level. The bottom consisting of a polyimide layer is critical to interfacial modulation, which shows the selectively binding capability with up‐dielectric layers to realize the modulation of charge transport, as corroborated by interface characterization and density functional‐based tight‐binding calculation. The findings provide an effective strategy for modulating the charge transport through polymer dielectric engineering and also recommend a podium to further comprehend the electrical characteristics of small molecules in organic thin‐film transistors.
The bilayer polymer dielectrics are constructed by bottom‐up method, and the theoretical analysis and characterization results show that the bottom polyimide (PI) is the key to achieve band‐like transport. There is “Lego‐like” tight combination between PI and the upper polyphenylene ether, polyacrylic acid, and poly(4‐vinylphenol), which enables the devices to achieve the regulation of organic small molecule thin film FETs from the thermal activated mode to the high‐quality band‐like transport.
A surface-potential-based drain current model is presented for ambipolar organic thin-film transistors (OTFTs). First, following the multiple trapping and release (MTR) conduction mechanism, a drain ...current model is presented for unipolar OTFTs considering exponentially distributed trap state density in the energy gap of an organic semiconductor. Next, from the model for unipolar OTFTs, analyzing electrons or (and) holes in different regimes, the model for ambipolar OTFTs is presented. The presented model can describe the drain current by compact expressions and can estimate the trap states density. The model is verified by available experimental data considering temperature characteristics.
Two new bithiophene imide (BTI)‐based n‐type polymers were synthesized. f‐BTI2‐FT based on a fused BTI dimer showed a smaller band gap, a lower LUMO, and higher crystallinity than s‐BTI2‐FT ...containing a BTI dimer connected through a single bond. s‐BTI2‐FT exhibited a remarkable electron mobility of 0.82 cm2 V−1 s−1, and f‐BTI2‐FT showed a further improved mobility of 1.13 cm2 V−1 s−1 in transistors. When blended with the polymer donor PTB7‐Th, f‐BTI2‐FT‐based all‐polymer solar cells (all‐PSCs) attained a PCE of 6.85 %, the highest value for an all‐PSC not based on naphthalene (or perylene) diimide polymer acceptors. However, s‐BTI2‐FT all‐PSCs showed nearly no photovoltaic effect. The results demonstrate that f‐BTI2‐FT is one of most promising n‐type polymers and that ring fusion offers an effective approach for designing polymers with improved electrical properties.
Best used fused: Two bithiophene imide (BTI)‐based n‐type polymer semiconductors were synthesized and characterized (see structures). Both showed substantial electron mobilities in organic thin‐film transistors; however, ring fusion of the BTI dimer drastically increased the device performance of the resulting polymer in all‐polymer solar cells, with remarkable power‐conversion efficiency up to 6.85 % and a large open‐circuit voltage of 1.04 V.
Transfer characteristics of ZnO thin‐film transistors (TFTs) based on ZnO doped with various alkali metals. A new doping method is demonstrated by employing alkali metals to achieve high‐performance ...and solution‐processed ZnO TFTs with a low processing temperature (∼300 °C), which is applicable to flexible plastic substrates.
Recently, reducing the operating voltage of metal oxide transistors has become a priority because this enables their use in wearable electronics where low power consumption is a requirement. Here, we ...fabricate transistors that operate under low driving voltage after adding a solution-processed, tungsten-doped indium oxide (IWO) semiconductor deposited on top of a 20 nm aluminum oxide transparent high-k dielectric. To analyze the effect of the tungsten content on the characteristics of IWO thin film transistors (TFTs), devices based on films with 0.11, 0.22, and 0.34 mol% tungsten content were fabricated and compared to pristine indium oxide-based TFTs. Optimized tungsten (W) content at 0.11 mol% achieves a fivefold improvement in the charge carrier mobility, an ON/ OFF current ratio two orders of magnitude higher, and the subthreshold swing decreased to less than 0.1 V/dec. The bias stability of the device with optimal W concentration is also significantly better than undoped In2O3-based TFTs, probably because doping effectively suppresses the generation of oxygen vacancies in the IWO active channel layer and improves device stability. To test the feasibility of IWO devices in practical applications, a load-type inverter was fabricated using the optimally doped film.
High fatigue resistance, bistability, and drastic property changes among isomers allow efficient modulation of the current output of organic thin‐film transistors (OTFTs) to be obtained by a ...photogating of the charge‐injection mechanism.
Since the report of the first diketopyrrolopyrrole (DPP)‐based polymer semiconductor, such polymers have received considerable attention as a promising candidate for high‐performance polymer ...semiconductors in organic thin‐film transistors (OTFTs). This Progress Report summarizes the advances in the molecular design of high‐mobility DPP‐based polymers reported in the last few years, especially focusing on the molecular design of these polymers in respect of tuning the backbone and side chains, and discussing the influences of structural modification of the backbone and side chains on the properties and device performance of corresponding DPP‐based polymers. This provides insights for the development of new and high‐mobility polymer semiconductors.
The advances in molecular design of high‐mobility DPP‐based polymers reported in the past few years are summarized, focusing on the strategy for synthesis of these polymers with respect to tuning the backbone and side chains. The relationships between the chemical structure, molecular packing, transistor characteristics, for example, are discussed.
A spontaneous patterning technique via parallel vacuum ultraviolet is developed for fabricating large‐scale, complex electronic circuits with 1 μm resolution. The prepared organic thin‐film ...transistors exhibit a low contact resistance of 1.5 kΩ cm, and high mobilities of 0.3 and 1.5 cm2 V−1 s−1 in the devices with channel lengths of 1 and 5 μm, respectively.
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