Vinylene and benzo[c][1,2,5]thiadiazole: effect of the π-spacer unit on the properties of bis(2-oxoindolin-3-ylidene)-benzodifuran-dione containing polymers for n-channel organic field-effect transistors

Two polymers based on (3E,7E)-3,7-bis(2-oxoindolin-3-ylidene)benzo[1,2-b:4,5-b′]difuran-2,6(3H,7H)-dione (BIBDF) coupled with (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) or dithienylbenzothiadiazole (TBT), namely PBIBDF-TVT and PBIBDF-TBT were synthesized via the Stille coupling reaction. The effect of benzothiadiazole or vinylene-π spacer of the copolymers on optical properties, energy levels, electronic device performance and microstructure were studied. It was found that PBIBDF-TBT based OFET devices, annealed at 180 °C, showed better performance with the highest electron mobility of 2.9 × 10⁻² cm² V s⁻¹ whereas PBIBDF-TVT polymer exhibited 5.0 × 10⁻⁴ cm² V s⁻¹. The two orders of magnitude higher electron mobility of PBIBDF-TBT over PBIBDT-TVT is a clear indicator of the better charge transport ability of this polymer semiconductor arising from its higher crystallinity and better donor–acceptor interaction.

Bottom-gate-top-contact OFET device structure using PBIBDF-TVT and PBIBDF-TBT based polymer semiconductors.     

Gel-based precursors for the high-performance of n-channel GaInSnZnO and p-channel CuGaSnSO thin-film transistors

The performance of metal–oxide thin-film transistors (TFTs) should be further improved for the applications of next-generation displays. Here, the developments of gel-derived gallium–indium–tin–zinc oxide (GITZO) for n-channel and copper–gallium–tin–sulfide oxide (CGTSO) for p-channel TFTs are demonstrated. The a-GITZO film by gel-based precursor gives an excellent interface with ZrO_x compared to the GITZO deposited using pristine or purified precursor. The gel-derived GITZO TFT exhibits the saturation mobility (μ_sat) of 28.6 ± 2.15 cm² V⁻¹ s⁻¹, three-fold higher than the pristine one, and excellent bias stability. The boost in GITZO TFT performances is due to the purity of the metal oxide material and higher film density with smooth surface morphology. In addition, the field-effect mobility (μ_FE) of the p-channel copper–tin–sulfide–gallium oxide (CGTSO) TFT could be increased from 1.71 to 4.25 cm² V⁻¹ s⁻¹ using a gel-derived precursor solution. Therefore, these results demonstrate that the gel-derived metal–oxide precursor by the solution process is a promising one for the high performance of the TFT backplane.

The performance of metal–oxide TFTs should be further improved for the applications of next-generation displays. Here, the developments of gel-derived GITZO for n-channel and CGTSO for p-channel TFTs are demonstrated.     

Intense-pulsed-UV-converted perhydropolysilazane gate dielectrics for organic field-effect transistors and logic gates

We fabricated a high-quality perhydropolysilazane (PHPS)-derived SiO₂ film by intense pulsed UV irradiation and applied it as a gate dielectric layer in high-performance organic field-effect transistors (OFETs) and complementary inverters. The conversion process of PHPS to SiO₂ was optimized by varying the number of intense pulses and applied voltage. The chemical structure and gate dielectric properties of the PHPS-derived SiO₂ films were systematically investigated via Fourier transform infrared spectroscopy and leakage current measurements, respectively. The resulting PHPS-derived SiO₂ gate dielectric layer showed a dielectric constant of 3.8 at 1 MHz and a leakage current density of 9.7 × 10⁻¹² A cm⁻² at 4.0 MV cm⁻¹. The PHPS-derived SiO₂ film was utilized as a gate dielectric for fabricating benchmark p- and n-channel OFETs based on pentacene and N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈), respectively. The resulting OFETs exhibited good electrical properties, such as carrier mobilities of 0.16 (±0.01) cm² V⁻¹ s⁻¹ (for the pentacene OFET) and 0.02 (±0.01) cm² V⁻¹ s⁻¹ (for the PTCDI-C₈ OFET) and an on–off current ratio larger than 10⁵. The fabrication of the PHPS-derived SiO₂ gate dielectric layer by a simple solution process and intense pulsed UV irradiation at room temperature serves as a novel approach for the realization of large-area flexible electronics in the flexible device industry of the future.

We fabricated a high-quality perhydropolysilazane (PHPS)-derived SiO₂ film by intense pulsed UV irradiation and applied it as a gate dielectric layer in high-performance organic field-effect transistors (OFETs) and complementary inverters.     

Green and low-cost synthesis of zinc oxide nanoparticles and their application in transistor-based carbon monoxide sensing

There has been steady progress in developing reliable and cost-effective strategies for the clean production of zinc oxide (ZnO) nanoparticles (NPs) owing to their unique structural and wide functional characteristics. While the green synthesis of such NPs from plant extracts has emerged as a sustainable and eco-friendly protocol, it is greatly restricted owing to the scarcity of potential natural precursors necessitating comprehensive investigations in this direction. Herein, we report a facile, low-cost green synthesis and characterization of ZnO NPs along with the demonstration of their usage as an active media in organic field-effect transistor (OFET) devices for sensing carbon monoxide (CO) gas. The ZnO NPs obtained from Nelumbo nucifera (lotus) leaf extract-mediated solution combustion synthesis at a much lower initiation temperature, the first of its kind, were characterized by various techniques such as UV-vis spectroscopy, XRD, EDX analysis, TEM and FESEM. The data derived from these experiments clearly evidence the formation of very pure and crystalline ZnO NPs possessing nearly spherical-shape with a size of 3–4 nm. The p-type organic field-effect transistor (OFET) device, fabricated using poly(3-hexylthiophene-2,5-diyl) (P3HT) and ZnO NPs, showed a field-effect mobility of 10⁻² cm² V⁻¹ sec⁻¹ with a slightly enhanced response of detecting CO gas at room temperature (RT). The phenomenon was further confirmed by the variation in electrical parameters of the OFET such as field-effect mobility (μ), on-current (I_on), and off-current (I_off). The selectivity and sensitivity of the fabricated device in CO gas detection was found to be more prominent than the other reducing gases (hydrogen sulphide, H₂S and ammonia, NH₃) and methanol vapours tested.

An OFET-based CO gas sensor has been demonstrated where ZnO NPs realized by an inexpensive, environmentally friendly method have been employed as an active medium.     

Ambipolar organic phototransistors based on 6,6′-dibromoindigo

Ambipolar organic phototransistors were fabricated using a natural pigment 6,6′-dibromoindigo (6-BrIG) as the active channel. These phototransistors yielded significantly enhanced currents upon light illumination with photoresponsivities and external quantum efficiencies as high as 10.3 A W⁻¹ and 2437% for the n-channel, and 55.4 mA W⁻¹ and 13.1% for the p-channel, respectively. In addition, simple inverter complementary circuits were fabricated by integrating two ambipolar phototransistors. Channel current was dependent on light intensity and voltage bias. This study provides a basis for an in-depth understanding of the optoelectronic characteristics of 6-BrIG, and introduces this material as an ecofriendly candidate for optoelectronic applications.

Ambipolar phototransistors with a natural pigment, 6,6′-dibromoindigo (6-BrIG or tyrian purple), have been investigated.     

Fabrication of ring oscillators using organic molecules of phenacene and perylenedicarboximide

Organic field-effect transistors (FETs) can be applied to radio-frequency identification tags (RFIDs) and active-matrix flat-panel displays. For RFID application, a cardinal functional block is a ring oscillator using an odd number of inverters to convert DC voltage to AC. Herein, we report the properties of two ring oscillators, one formed with [6]phenacene for a p-channel FET and N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) for an n-channel FET, and one formed with 3,10-ditetradecylpicene ((C₁₄H₂₉)₂-picene) for a p-channel FET and PTCDI-C8 for an n-channel FET. The former ring oscillator provided a maximum oscillation frequency, f_osc of 26 Hz, and the latter a maximum f_osc of 21 Hz. The drain–drain voltage, V_DD, applied to these ring oscillators was 100 V. This may be the first step towards a future practical ring oscillator using phenacene molecules. The values of field-effect mobility, μ in the p-channel [6]phenacene FET and n-channel PTCDI-C8 FET, which form the building blocks in the ring oscillator with an f_osc value of 26 Hz, are 1.19 and 1.50 × 10⁻¹ cm² V⁻¹ s⁻¹, respectively, while the values in the p-channel (C₁₄H₂₉)₂-picene FET and n-channel PTCDI-C8 FET, which form the ring oscillator with an f_osc of 21 Hz, are 1.85 and 1.54 × 10⁻¹ cm² V⁻¹ s⁻¹, respectively. The μ values in the p-channel FETs are higher by one order of magnitude than those of the n-channel FET, which must be addressed to increase the value of f_osc. Finally, we fabricated a ring oscillator with ZrO₂ instead of parylene for the gate dielectric, which provided the low-voltage operation of the ring oscillator, in which [6]phenacene and PTCDI-C8 thin-film FETs were employed. The value of f_osc obtained in the ring oscillator was 24 Hz. In this ring oscillator, the V_DD value applied was limited to 20 V. The durability of the ring oscillators was also investigated, and the bias stress effect on the f_osc and the amplitude of the output voltage, V_out are discussed. This successful operation of ring oscillators represents an important step towards the realization of future practical integrated logic gate circuits using phenacene molecules.

A ring oscillator consisting of p-channel and n-channel organic FETs.     

MoS2/polyaniline/functionalized carbon cloth electrode materials for excellent supercapacitor performance

In this study, molybdenum disulfide (MoS₂), polyaniline (PANI) and their composite (MoS₂/PANI) were facilely prepared via a liquid-phase method and in situ polymerization. An MoS₂/PANI/functionalized carbon cloth (MoS₂/PANI/FCC) was facilely constructed by a drop-casting method. MoS₂/PANI-10/FCC displays remarkable electrochemical performances, and its specific capacitances varied from 452.25 to 355.5 F g⁻¹ at current densities ranging from 0.2 to 4 A g⁻¹, which were higher than those of MoS₂/CC (from 56.525 to 7.5 F g⁻¹) and pure PANI/CC (319.5 to 248.5 F g⁻¹), respectively. More importantly, the MoS₂-10/PANI/FCC electrode has a long cycling life, and a capacity retention of 87% was obtained after 1000 cycles at a large current density of 10 A g⁻¹. Moreover, the MoS₂/PANI-10/FCC-based symmetric supercapacitor also exhibits excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 72.8 F g⁻¹ at a current density of 0.2 A g⁻¹ and the capacitance retention of 85% is obtained after 1000 cycles.

A MoS₂/PANI/functionalized carbon cloth (MoS₂/PANI/FCC) was constructed by a drop-casting method. Its specific capacitances were higher than those of MoS₂/CC and pure PANI/CC.     

Design,synthesis, theoretical study,antioxidant, and anticholinesterase activities of new pyrazolo-fused phenanthrolines

Pyrazole-fused phenanthroline compounds were obtained through several synthetic routes. NMR, HRMS, and IR techniques were used to characterize and confirm the chemical structures. Crystal structures were obtained from compounds 3a, 5b, 5j, 5k, and 5n and analyzed using X-ray diffraction. Compounds were evaluated as acetyl (AChE) and butyrylcholinesterase (BChE) inhibitors, and the results showed a moderate activity. Compound 5c presented the best activity against AChE (IC₅₀ = 53.29 μM) and compound 5l against BChE enzyme (IC₅₀ = 119.3 μM). Furthermore, the ability of the synthetic compounds to scavenge cationic radicals DPPH and ABTS was evaluated. Compound 5e (EC₅₀ = 26.71 μg mL⁻¹) presented the best results in the DPPH assay, and compounds 5e, 5f and 5g (EC₅₀ = 11.51, 3.10 and <3 μg mL⁻¹, respectively) showed better ABTS cationic radical scavenging results. Finally, in silico analyses indicated that 71% of the compounds show good oral availability and are within the ranges established by the Lipinski criteria.

Different synthetic strategies were used to optimize, obtaining a series of compounds derived from the pyrazole-fused phenanthroline system.     

Ag decorated silica nanostructures for surface plasmon enhanced photocatalysis

In this article, we present a novel synthesis of mesoporous SiO₂/Ag nanostructures for dye (methylene blue) adsorption and surface plasmon mediated photocatalysis. Mesoporous SiO₂ nanoparticles with a pore size of 3.2 nm were synthesized using cetyltrimethylammonium bromide as a structure directing agent and functionalized with (3-aminopropyl)trimethoxysilane to introduce amine groups. The adsorption behavior of non-porous SiO₂ nanoparticles was compared with that of the mesoporous silica nanoparticles. The large surface area and higher porosity of mesoporous SiO₂ facilitated better adsorption of the dye as compared to the non-porous silica. Ag decorated SiO₂ nanoparticles were synthesized by attaching silver (Ag) nanoparticles of different morphologies, i.e. spherical and triangular, on amine functionalized silica. The photocatalytic activity of the mesoporous SiO₂/Ag was compared with that of non-porous SiO₂/Ag nanoparticles and pristine Ag nanoparticles. Mesoporous SiO₂ nanoparticles (k_d = 31.3 × 10⁻³ g mg⁻¹ min⁻¹) showed remarkable improvement in the rate of degradation of methylene blue as compared to non-porous SiO₂ (k_d = 25.1 × 10⁻³ g mg⁻¹ min⁻¹) and pristine Ag nanoparticles (k_d = 19.3 × 10⁻³ g mg⁻¹ min⁻¹). Blue Ag nanoparticles, owing to their better charge carrier generation and enhanced surface plasmon resonance, exhibited superior photocatalysis performance as compared to yellow Ag nanoparticles in all nanostructures.

In this article, we present a novel synthesis of mesoporous SiO₂/Ag nanostructures for dye (methylene blue) adsorption and surface plasmon mediated photocatalysis.     

Tinospora cordifolia derived biomass functionalized ZnO particles for effective removal of lead(ii), iron(iii), phosphate and arsenic(iii) from water

Owing to the vast diversity in functional groups and cost effectiveness, biomass can be used for various applications. In the present study, biomass from Tinospora cordifolia (TnC) was prepared and grafted onto the surface of ZnO particles following a simple method. The TnC functionalized ZnO particles (ZnO@TnC) were characterized and exhibited excellent adsorption properties towards Pb²⁺ (506 mg g⁻¹), Fe³⁺ (358 mg g⁻¹) and PO₄³⁻ (1606 mg g⁻¹) and the Fe³⁺ adsorbed ZnO@TnC adsorbs AsO₂¹⁻ (189 mg g⁻¹); the metal ions and anions were analyzed by ICP and IC. For reuse of ZnO@TnC, a desorption study was successfully carried out using NaOH and EDTA for PO₄³⁻ and Pb²⁺, respectively; Fe³⁺ was further used for adsorption of As(iii). The adsorption fits well with the Langmuir adsorption isotherm model and the adsorption kinetic data are best fitted with a pseudo-second-order equation. The system developed may be useful for treatment of waste water and industrial effluents.

Owing to the vast diversity in functional groups and cost effectiveness, biomass can be used for various applications.     

Dual role of Ag nanowires in ZnO quantum dot/Ag nanowire hybrid channel photo thin film transistors

High mobility and p-type thin film transistors (TFTs) are in urgent need for high-speed electronic devices. In this work, ZnO quantum dot (QD)/Ag nanowire (NW) channel TFTs were fabricated by a solution processed method. The Ag NWs play the dual role of dopant and providing the charge transfer route, which make the channel p-type and enhance its mobility, respectively. The best sample yields an on/off ratio (I_on/I_off) of 5.04 × 10⁵, a threshold voltage (V_T) of 0.73 V, a high field effect mobility (μ_FE) of 8.69 cm² V⁻¹ s⁻¹, and a subthreshold swing (SS) of 0.41 V dec⁻¹. Owing to the strong ultraviolet (UV) absorption and photo-induced carrier separation ability of ZnO QDs and the fast carrier transport of Ag NWs, the devices acquire a high external quantum efficiency (EQE) and ultra-fast response under 365 nm UV illumination. The UV-modulated ZnO QD/Ag NW hybrid channel photo TFTs have potential for future application in optoelectronic devices, such as photodetectors and photoswitches.

High mobility and p-type thin film transistors (TFTs) are in urgent need for high-speed electronic devices.     

A hybrid inorganic–organic light-emitting diode using Ti-doped ZrO2 as an electron-injection layer

We have fabricated stable efficient iridium(iii)-bis-5-(1-(naphthalene-1-yl)-1H-phenanthro[9,10-d]imidazole-2-yl) benzene-1,2,3-triol (acetylacetonate) [Ir(NPIBT)₂ (acac)] doped inverted bottom-emissive green organic light-emitting diodes using Ti-doped ZrO₂ nanomaterials as the electron injection layer. The current density (J) and luminance (L) of the fabricated devices with Ti-doped ZrO₂ deposited between an indium tin oxide cathode and an Ir(NPIBT)₂ (acac) emissive layer increased significantly at a low driving voltage (V) compared with control devices without Ti-doped ZrO₂. The Ti-doped ZrO₂ layer can facilitate the electron injection effectively and enhances the current efficiency (η_c) of 2.84 cd A⁻¹ and power efficiency (η_p) of 1.32 lm W⁻¹

Ti-doped ZrO₂ facilitates electron injection effectively, leading to enhanced current efficiency of 2.84 cd A⁻¹ and power efficiency of 1.32 lm W⁻¹     

Synthesis,oxide formation,properties and thin film transistor properties of yttrium and aluminium oxide thin films employing a molecular-based precursor route

Combustion synthesis of dielectric yttrium oxide and aluminium oxide thin films is possible by introducing a molecular single-source precursor approach employing a newly designed nitro functionalized malonato complex of yttrium (Y-DEM-NO₂1) as well as defined urea nitrate coordination compounds of yttrium (Y-UN 2) and aluminium (Al-UN 3). All new precursor compounds were extensively characterized by spectroscopic techniques (NMR/IR) as well as by single-crystal structure analysis for both urea nitrate coordination compounds. The thermal decomposition of the precursors 1–3 was studied by means of differential scanning calorimetry (DSC) and thermogravimetry coupled with mass spectrometry and infrared spectroscopy (TG-MS/IR). As a result, a controlled thermal conversion of the precursors into dielectric thin films could be achieved. These oxidic thin films integrated within capacitor devices are exhibiting excellent dielectric behaviour in the temperature range between 250 and 350 °C, with areal capacity values up to 250 nF cm⁻², leakage current densities below 1.0 × 10⁻⁹ A cm⁻² (at 1 MV cm⁻¹) and breakdown voltages above 2 MV cm⁻¹. Thereby the increase in performance at higher temperatures can be attributed to the gradual conversion of the intermediate hydroxy species into the respective metal oxide which is confirmed by X-ray photoelectron spectroscopy (XPS). Finally, a solution-processed Y_xO_y based TFT was fabricated employing the precursor Y-DEM-NO₂1. The device exhibits decent TFT characteristics with a saturation mobility (μ_sat) of 2.1 cm² V⁻¹ s⁻¹, a threshold voltage (V_th) of 6.9 V and an on/off current ratio (I_on/off) of 7.6 × 10⁵.

Transformation of a new molecular precursor allows the formation of yttrium oxide under moderate conditions displaying high voltage breakthrough behaviour.     

Facile synthesis of picenes incorporating imide moieties at both edges of the molecule and their application to n-channel field-effect transistors

Picene derivatives incorporating imide moieties along the long-axis direction of the picene core (C_n-PicDIs) were conveniently synthesized through a four-step synthesis. Photochemical cyclization of dinaphthylethenes was used as the key step for constructing the picene skeleton. Field-effect transistor (FET) devices of C_n-PicDIs were fabricated by using ZrO₂ as a gate substrate and their FET characteristics were investigated. The FET devices showed normally-off n-channel operation; the averaged electron mobility (μ) was evaluated to be 2(1) × 10⁻⁴, 1.0(6) × 10⁻¹ and 1.4(3) × 10⁻² cm² V⁻¹ s⁻¹ for C₄-PicDI, C₈-PicDI and C₁₂-PicDI, respectively. The maximum μ value as high as 2.0 × 10⁻¹ cm² V⁻¹ s⁻¹ was observed for C₈-PicDI. The electronic spectra of C_n-PicDIs in solution showed the same profiles irrespective of the alkyl chain lengths. In contrast, in thin films, the UV absorption and photoelectron yield spectroscopy (PYS) indicated that the lowest unoccupied molecular orbital (LUMO) level of C_n-PicDIs gradually lowered upon the elongation of the alkyl chains, suggesting that the alkyl chains modify intermolecular interactions between the C_n-PicDI molecules in thin films. The present results provide a new strategy for constructing a high performance n-channel organic semiconductor material by utilizing the electronic features of phenacenes.

Picenediimide derivatives serve as the active layer of n-channel thin-film field-effect transistors displaying a maximum charge carrier mobility as high as 2.0 × 10⁻¹ cm² V⁻¹ s⁻¹.     

Fully solution-induced high performance indium oxide thin film transistors with ZrOx high-k gate dielectrics

Solution based deposition has been recently considered as a viable option for low-cost flexible electronics. In this context, research efforts have been increasingly focused on the development of suitable solution-processed materials for oxide based transistors. In this work, we report a fully solution synthesis route, using 2-methoxyethanol as solvent, for the preparation of In₂O₃ thin films and ZrO_x gate dielectrics, as well as the fabrication of In₂O₃-based TFTs. To verify the possible applications of ZrO_x thin films as the gate dielectric in complementary metal oxide semiconductor (CMOS) electronics, fully solution-induced In₂O₃ TFTs based on ZrO₂ dielectrics have been integrated and investigated. The devices, with an optimized annealing temperature of 300 °C, have demonstrated high electrical performance and operational stability at a low voltage of 2 V, including a high μ_sat of 4.42 cm² V⁻¹ s⁻¹, low threshold voltage of 0.31 V, threshold voltage shift of 0.15 V under positive bias stress for 7200 s, and large I_on/I_off of 7.5 × 10⁷, respectively. The as-fabricated In₂O₃/ZrO_x TFTs enable fully solution-derived oxide TFTs for potential application in portable and low-power consumption electronics.

Solution based deposition has been recently considered as a viable option for low-cost flexible electronics.     

Synthesis of 1,3-dicarbonyl-functionalized reduced graphene oxide/MnO2 composites and their electrochemical properties as supercapacitors

A novel 1,3-dicarbonyl-functionalized reduced graphene oxide (rDGO) was prepared by N-(4-aminophenyl)-3-oxobutanamide interacting with the epoxy and carboxyl groups of graphene oxide. The high-performance composite supercapacitor electrode material based on MnO₂ nanoparticles deposited onto the rDGO sheet (DGM) was fabricated by a hydrothermal method. The morphology and microstructure of the composites were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman microscopy and X-ray photoelectron spectroscopy. The obtained results indicated that MnO₂ was successfully deposited on rDGO surfaces. The formed composite electrode materials exhibit excellent electrochemical properties. A specific capacitance of 267.4 F g⁻¹ was obtained at a current density of 0.5 A g⁻¹ in 1 mol L⁻¹ H₂SO₄, while maintaining high cycling stability with 97.7% of its initial capacitance after 1000 cycles at a current density of 3 A g⁻¹. These encouraging results are useful for potential energy storage device applications in high-performance supercapacitors.

A novel functionalized reduced graphene oxide and MnO₂ composite was prepared as a supercapacitor electrode material.     

Benzohexacene guide in accurate determination of field effect carrier mobilities in long acenes

Oligoacenes are promising materials in the field of electronic devices since they exhibit high charge carrier mobility and more particularly as a semiconductor in thin film transistors. Herein, we investigate the field effect charge carrier mobility of benzohexacene, recently obtained by cheletropic decarbonylation at moderate temperature. Initially, high performance bottom contact organic thin-film transistors (OTFTs) were fabricated using tetracene to validate the fabrication process. For easier comparison, the geometries and channel sizes of the fabricated devices are the same for the two acenes. The charge transport in OTFTs being closely related to the organic thin film at the dielectric/organic semiconductor interface, the structural and morphological features of the thin films of both materials are therefore studied according to deposition conditions. Finally, by extracting relevant device parameters the benzohexacene based OTFT shows a four-probe contact-corrected hole mobility value of up to 0.2 cm² V⁻¹ s⁻¹.

Four-probes mobility vs. V_GS in the linear regime (V_DS = −10 V) for benzohexacene based transistor.     

Naphthalene diimide-based n-type small molecule organic mixed conductors for accumulation mode organic electrochemical transistors

Organic mixed ionic-electronic conductors (OMIECs), which transport both ionic and electronic charges, development are important for progressing bioelectronic and energy storage devices. The p-type OMIECs are extensively investigated and used in various applications, whereas the n-type ones lag far behind due to their moisture and air instability. Here, we report the synthesis of the novel n-type naphthalene diimide (NDI)-based small-molecule OMIECs for organic electrochemical transistors (OECTs). The electro-active NDI molecule with the linear ethylene glycol side chains is a promising candidate for n-type channel material to obtain accumulation mode OECTs. This NDI-based small-molecule OMIEC, gNDI-Br₂, demonstrates ion permeability due to the attachment of the glycol side chains with optimized ionic-electronic conductions. OECT devices with gNDI-Br₂ channel material displays excellent performance in water and ambient stability. OECTs fabricated with two different concentrations, 50 mg mL⁻¹ and 100 mg mL⁻¹ of gNDI-Br₂ demonstrate a transconductance value of 344 ± 19.7 μS and 814 ± 124.2 μS with the mobility capacitance product (μC*) of 0.13 ± 0.03 F cm⁻¹ V⁻¹ s⁻¹ and 0.23 ± 0.04 F cm⁻¹ V⁻¹ s⁻¹, respectively. These results demonstrate the n-type OMIEC behaviour of the NDI-based small-molecule and its applicability as an OECT channel material.

There are few n-type organic mixed ionic-electronic conductors (OMIECs) for accumulation mode devices. gNDI-Br₂, an n-type OMIEC has been developed for device applications in the area of biosensing and energy storage.     

Flexible and high energy density solid-state asymmetric supercapacitor based on polythiophene nanocomposites and charcoal

An asymmetric supercapacitor (ASC) was constructed using a polythiophene/aluminium oxide (PTHA) nanocomposite as an anode electrode and charcoal as a cathode electrode. The highest specific capacitance (C_sp) of the PTHA electrode was found to be 554.03 F g⁻¹ at a current density (CD) of 1 A g⁻¹ and that of the charcoal electrode was 374.71 F g⁻¹ at 1.4 A g⁻¹, measured using a three electrode system. The maximum C_sp obtained for the assembled PTHA//charcoal asymmetric supercapacitor (ASC) was 265.14 F g⁻¹ at 2 A g⁻¹. It also showed a high energy density of 42.0 W h kg⁻¹ at a power density of 735.86 W kg⁻¹ and capacitance retention of 94.61% even after 2000 cycles. Moreover, it is worth mentioning that the asymmetric device was used to illuminate a light emitting diode (LED) for more than 15 minutes. This PTHA//charcoal ASC also possesses stable electrochemical properties in different bending positions and hence finds a promising application in flexible, wearable and portable energy storage electronic devices.

A high energy density flexible solid-state asymmetric supercapacitor is fabricated using polythiophene nanocomposites and charcoal which exhibits stable electrochemical properties in different bending position.     

The application of a non-doped composite hole transport layer of [MoO3/CBP]n with multi-periodic structure for high power efficiency organic light-emitting diodes

A non-doped multi-periodic structure of composite hole transport layer of [MoO₃/CBP]_n was applied to organic light-emitting diodes. All devices with such hole transport layers showed low turn-on voltage of about 3 V, ultra-high luminance of >110 000 cd m⁻², high current efficiency of >50 cd A⁻¹, and high EQE of more than 15%. The optimized device exhibited power efficiency increase of 66% and 18% relative to the single periodic and doped structure OLEDs. The achievement of the reduced driving voltage and improved power efficiency can be attributed to the significantly enhanced hole injection and transport induced by the multi-periodic structure of composite hole transport layer, which was demonstrated via a series of hole-only devices. For improved hole injection and transport mechanism, we also provided a detailed discussion in combination with atomic force microscopy measurements.

A non-doped multi-periodic structure of composite hole transport layer of [MoO₃/CBP]_n was applied to organic light-emitting diodes.