Nanoparticle-dispersed high-k organic–inorganic hybrid dielectrics for organic thin-film transistors

We fabricated solution-processable thin gate dielectrics for organic thin-film transistors (OTFTs) using an organosiloxane-based organic–inorganic hybrid material. The electrical characteristics of the hybrid dielectrics were controlled by adjusting the zirconium alkoxide concentration. Microstructural observation and chemical analysis allow us to determine the influence of microstructure and composition on the electrical properties of the hybrid dielectrics. Our hybrid material is composed of three phases: ZrO₂, ZrSiO₄, and organosiloxane. OTFTs based on the hybrid dielectrics exhibited better electrical performance compared to transistors based on poly(4-vinylphenol) (PVP). Using a dielectric with a higher dielectric constant and fewer hydroxyl groups enabled us to fabricate a transistor with a lower off-current, higher on/off current ratio, and lower threshold voltage.     

UV-curable organic–inorganic hybrid gate dielectrics for organic thin film transistors

UV-curable hybrid thin films were prepared from ZrO₂ hybrid sols containing the acrylic monomer, DPHA, on substrates. The prepared ZrO₂ hybrid sols showed long-term storage stability. Hybrid dielectrics were prepared by sol–gel process and UV cross-linking below 160 °C. Leakage currents of dielectric layers remained below 10⁻⁶ A in 2 MV/cm and dielectric constants were measured to be 3.85–4 at 1 kHz. In addition, organic–inorganic hybrid thin films have smooth and hydrophobic surface. Pentacene OTFTs with thin hybrid dielectrics exhibit of mobility as large as 2.5 cm²/V s, subthreshold swing as low as 0.2 V/decade, an on–off ratio of 10⁵. These results demonstrated that UV-curable sol–gel hybrid systems are suitable for gate dielectrics in OTFTs.     

High-efficiency hybrid organic–inorganic light-emitting devices

We report efficient red, orange, green and blue organic–inorganic light emitting devices using light emitting polymers and polyethylenimine ethoxylated (PEIE) interlayer with the respective luminance efficiency of 1.3, 2.7, 10 and 4.1 cd A⁻¹, which is comparable to that of the analogous conventional devices using a low work-function metal cathode. This is enabled by the enhanced electron injection due to the effective reduction of the ZnO work-function by PEIE, as well as hole/exciton-blocking function of PEIE layer. Due to the benign compatibility between PEIE and the neighboring organic layer, the novel phosphorescent organic–inorganic devices using solution-processed small molecule emissive layer show the maximum luminance efficiency of 87.6 cd A⁻¹ and external quantum efficiency of 20.9% at 1000 cd m⁻².     

New hybrid organic–inorganic sol–gel positive resist

The direct nanopatterning of a novel hybrid organic–inorganic sol–gel film based on bridged polysilsesquioxanes (BPS) using X-ray synchrotron radiation is reported. The main advantages of a direct fabrication technique with respect to conventional photolithography are represented by the possibility to bypass some typical post-exposure lithographic steps and to avoid the use of a sacrificial layer. The distinctive features rendering hybrid BPS-based material innovative for photolithographic applications are: the patternability as resist, the positive tone behaviour exhibited under X-ray irradiation, the porous structure demonstrated at low temperature, and the possibility to widely tailor material electro-optical and structural properties to experimental needs. A systematic investigation of the interactions between sol–gel BPS films based on the bis(triethoxysilyl)benzene precursor and soft X-rays is conducted. Under X-ray exposure, BPS-based films suffer structural changes attributed to the organic bridge breaking, and become soluble in suitable acidic aqueous solutions, producing final lithographies of sub-micron resolution, high contrast and good edge definition.     

A flexible moisture barrier comprised of a SiO2-embedded organic–inorganic hybrid nanocomposite and Al2O3 for thin-film encapsulation of OLEDs

We demonstrated a high performance flexible multi-barrier containing a silica nanoparticle-embedded organic–inorganic hybrid (S–H) nanocomposite and Al₂O₃. The multi-barrier was prepared by low-temperature Al₂O₃ atomic layer deposition and with a spin-coated S–H nanocomposite. The moisture barrier properties were investigated with a water vapor transmission rate (WVTR), estimated by a Ca test at 30 °C, 90% R.H.. Moisture diffusion was effectively suppressed by the sub-700 nm thick multi-barrier incorporating well-dispersed silica nanoparticles in the organic layer. A low WVTR of 1.14 × 10^?5 g/m² day and average transmittance of 85.8% in the visible region were obtained for the multi-barrier. After bending under tensile stress mode, the moisture barrier property of the multi-barriers was retained. The multi-barrier was successfully applied to thin-film encapsulation of OLEDs. The thin-film encapsulated OLEDs showed practicable current–voltage–luminance (I–V–L) characteristics and stable real operation over 700 h under ambient conditions.     

Solution-processed organic–inorganic hybrid CMOS inverter exhibiting a high gain reaching 890

In this letter, we present a fabrication scheme and device performances of an organic–inorganic hybrid CMOS inverter employing a high-performance p-type organic semiconductor and an amorphous metal oxide layers. A deterioration of the oxide layer during device processing, which is often found in solution-processed semiconductor oxides, can be avoided by a one-shot solution-crystallization technique utilizing a polymer-blend. Both the p- and the n-type channels exhibited excellent transistor performances with high carrier mobilities and with precipitous turn-on behaviors near the gate voltages of 0 V, resulting in a successful demonstration of an ideal CMOS inverter operation with gain of 890. This result will update a potential excellence of organic–inorganic hybrid CMOS circuits in practical devices.     

Enhancing light-extraction efficiency of OLEDs with high- and low-refractive-index organic–inorganic hybrid materials

High- and low-refractive-index hybrid materials were prepared by an in situ acid-free sol–gel process for internal and external light-extraction layers in organic light-emitting diodes (OLEDs). A random copolymer of methyl methacrylate (MMA) and 3-(trimethoxysilyl) propyl methacrylate (MSMA), poly(MMA-co-MSMA), which was capped with trialkoxysilane in MSMA units, was used as a precursor. The precursor was further reacted with titanium(IV) isopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) to synthesize the high- and low-refractive-index hybrid materials, respectively, in which TiO₂ and SiO₂ nanoparticles were well dispersed, respectively, in the polymer matrix. After the reactions with TTIP and TEOS, the refractive index increased to 1.81 and decreased to 1.44 from 1.50 of the precursor, respectively. The luminance, power, and current efficiency of the OLED with an external light-extraction layer were enhanced by 21.3, 28.6, and 29.1%, respectively, those of the OLED with an internal light-extraction layer were increased by 62.4, 76.9, and 59.2%, respectively, and those of the device with combined ELEL and ILEL were enhanced by 62.7, 77.2, and 59.3%, respectively, when compared to values for the reference OLED without an internal or external light-extraction layer. These results indicate that high- and low-refractive-index materials are desirable for enhancement in light-extraction efficiency, and they can provide practical solutions for various applications such as OLED displays and lighting.     

Electrical and photoelectrical properties of P3HT/n-Si hybrid organic–inorganic heterojunction solar cells

A detail analysis of electrical and photoelectrical properties of hybrid organic–inorganic heterojunction solar cells poly(3-hexylthiophene) (P3HT)/n-Si, fabricated by spin-coating of the polymeric thin film onto oxide passivated Si(1 0 0) surface, was carried out within the temperature ranging from 283 to 333 K. The dominating current transport mechanisms were established to be the multistep tunnel-recombination and space charge limited current at forward bias and leakage current through the shunt resistance at reverse bias. A simple approach was developed and successfully applied for the correct analysis of the high frequency C–V characteristics of hybrid heterojunction solar cells. The P3HT/n-Si solar cell under investigation possessed the following photoelectric parameters: J_sc = 16.25 mA/cm², V_oc = 0.456 V, FF = 0.45, η = 3.32% at 100 mW/cm² AM 1.5 illumination. The light dependence of the current transport mechanisms through the P3HT/n-Si hybrid solar cells is presented quantitatively and discussed in detail.     

Electrosynthesis of organic–inorganic compounds (p–n heterojunction)

An electrochemical deposition procedure by cyclic voltammetry, in an electrolyte solution was adopted for the preparation of thin films of polypyrrole–gallium arsenide composite materials. The properties of the composite layers were studied by cyclic voltammetry, electrochemical impedance spectroscopy and photoelectrochemical measurements. The p- and n-type semiconductor behaviour of the polypyrrole (PPy) and gallium arsenide (GaAs) were studied by photocurrent measurements. It was found that the composite material (PPy–GaAs) had a (p–n) heterojunction behaviour.     

Nonvolatile memory performance improvements for solution-processed thin-film transistors with composition-modified In–Zn–Ti–O active channel and ferroelectric copolymer gate insulator

The nonvolatile memory thin-film transistors (M-TFTs) using a solution-processed indium-zinc-titanium oxide (IZTiO) active channel and a poly(vinylidene fluoride-trifluoroethylene) ferroelectric gate insulator were fabricated and characterized to elucidate the relationships between the IZTiO channel composition and the memory performances such as program speed and data retention. The compositions of the spin-coated IZTiO layers were modified with different Ti amounts of 0, 2, 5, and 10 mol%. The carrier concentration of IZTiO channel layer was effectively modulated by the incorporated Ti amounts and the defect densities within the channel were effectively reduced by Ti incorporation. The M-TFT fabricated with IZTiO channel with 2-mol% Ti composition exhibited the best overall device performances, in which the μ_FE, SS, MW, and programmed I_on/off were obtained to be 23.6 cm² V^?1 s^?1, 701 mV/decade, 11.8 V, and 1.2 × 10⁵, respectively. Furthermore, thanks to the suitable amounts of Ti incorporation into the IZO, the improved program speed and data retention properties were successfully confirmed.     

Enhancement-mode In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors with sol–gel processed gate dielectrics

Enhancement-mode In_0.53Ga_0.47As n-type metal-oxide-semiconductor field-effect transistors (MOSFETs), with barium zirconate titanate (BZT) and titanium dioxide (TiO₂) high-κ materials prepared via the solution–gelation process as gate dielectrics, have been fabricated. The dielectric constants of BZT and TiO₂ are 6.67 and 19.3, respectively. The In_0.53Ga_0.47As MOSFET with TiO₂ exhibits better electrical characteristics than the In_0.53Ga_0.47As MOSFET with BZT. These characteristics include higher maximum drain current density, higher maximum transconductance, and smaller subthreshold swing.     

How small the contacts could be optimal for nanoscale organic transistors?

We report on a study seeking an optimized contact configuration for organic transistors that minimizes contact effects but maintains smallest contact size. We begin with the bulk access resistance in staggered transistors which results from the charge transport through the organic semiconductor film. Bulk access resistance is an intrinsic contributor to the contact resistance which has been little understood due to lack of a reliable study tool. In this work, we utilize the inner transported power inside the semiconductor film as a medium to investigate the contact resistance and the relevant contact effects. We examine the influences of the organic film thickness (t_SC), the channel length (L), the underlying charge transport and various organic semiconductor materials with variable carrier mobility. A roughly optimal contact length (L_C) of L_C0 ≈ 6t_SC is obtained. The results reveal that besides the device architecture the underlying charge transport should be also taken into account in designing organic transistors for practical application.     

MoO3–Au composite interfacial layer for high efficiency and air-stable organic solar cells

Efficient and stable polymer bulk-heterojunction solar cells based on regioregular poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PC₆₁BM) blend active layer have been fabricated with a MoO₃–Au co-evaporation composite film as the anode interfacial layer (AIL). The optical and electrical properties of the composite MoO₃–Au film can be tuned by altering the concentration of Au. A composite film with 30% (weight ratio) Au was used as the AIL and showed a better performance than both pure MoO₃ and PEDOT:PSS as AIL. The surface morphology of the MoO₃–Au composite film was investigated by atomic force microscopy (AFM) and showed that the originally rough ITO substrate became smooth after depositing the composite film, with the root mean square roughness (RMS) decreased from 4.08 nm to 1.81 nm. The smooth surface reduced the bias-dependent carrier recombination, resulting in a large shunt resistance and thus improving the fill factor and efficiency of the devices. Additionally, the air stability of devices with different AILs (MoO₃–Au composite, MoO₃ and PEDOT:PSS) were studied and it was found that the MoO₃–Au composite layer remarkably improved the stability of the solar cells with shelf life-time enhanced by more than 3 and 40 times compared with pure MoO₃ layer and PEDOT:PSS layer, respectively. We argue that the stability improvement might be related with the defect states in MoO₃ component.     

Strategies for ultralow-κ dielectrics for integrated-circuit interconnects

In the last years the original insulator for integrated circuit (IC) interconnects (SiO₂, with relative dielectric constant κ of 3.9) has been replaced first by chemical-vapor-deposited SiO_2−yH_2y (with κ decreasing with y) and now by spun-on silico-organo compounds or highly aromatic organics (with κ as low as 2.4). It is generally believed that the $\text{0.13}\text{μm}$ node will require insulators with κ<2.2, presumably not achievable by minor modifications of the known substances. Assuming the incompatibility of perfluorinated alkane with integrated-circuit processing, the region κ<2.2 will most likely require the use of porous materials. To separate the device active zones from the environment, the porous insulator must however have an impermeable cap. The ‘ultimate’ insulator architecture is thus imagined to be formed by a highly porous, thermally stable, insulator with κ close to 1 filling the intrametal regions and functioning as pillar for an overlying thin nonporous hole-free insulator functioning as a slab for the subsequent interconnecting layers. Integrating such a structure in the IC technology, however, is not trivial. This paper discusses how that might be achieved borrowing, combining and modifying known technologies.     

Effect of the anode-emitter injection efficiency on the characteristics of hybrid SIT–MOS transistors

The possibility of optimizing high-voltage hybrid SIT–MOP transistors (HSMTs) by means of a local reduction in lifetime near the anode emitter and/ or by decreasing its injection efficiency by three different methods is studied using two-dimensional numerical simulation. It is shown that all four optimization methods are equivalent from the physical point of view and make it possible to decrease the turn-off energy loss E_off by 30–40%, as in insulated gate bipolar transistors (IGBTs). However, all other conditions being equal, the energy E_off in the HSMT appeared 15–35% lower than in equivalent trench IGBTs.     

D–A copolymer with high ambipolar mobilities based on dithienothiophene and diketopyrrolopyrrole for polymer solar cells and organic field-effect transistors

Donor–acceptor (D–A) type conjugated polymers have been developed to absorb longer wavelength light in polymer solar cells (PSCs) and to achieve a high charge carrier mobility in organic field-effect transistors (OFETs). PDTDP, containing dithienothiophene (DTT) as the electron donor and diketopyrrolopyrrole (DPP) as the electron acceptor, was synthesized by stille polycondensation in order to achieve the advantages of D–A type conjugated polymers. The polymer showed optical band gaps of 1.44 and 1.42 eV in solution and in film, respectively, and a HOMO level of 5.09 eV. PDTDP and PC₇₁BM blends with 1,8-diiodooctane (DIO) exhibited improved performance in PSCs with a power conversion efficiency (PCE) of 4.45% under AM 1.5G irradiation. By investigating transmission electron microscopy (TEM), atomic force microscopy (AFM), and the light intensity dependence of J_SC and V_OC, we conclude that DIO acts as a processing additive that helps to form a nanoscale phase separation between donor and acceptor, resulting in an enhancement of μ_h and μ_e, which affects the J_SC, EQE, and PCE of PSCs. The charge carrier mobilities of PDTDP in OFETs were also investigated at various annealing temperatures and the polymer exhibited the highest hole and electron mobilities of 2.53 cm² V⁻¹ s⁻¹ at 250 °C and 0.36 cm² V⁻¹ s⁻¹ at 310 °C, respectively. XRD and AFM results demonstrated that the thermal annealing temperature had a critical effect on the changes in the crystallinity and morphology of the polymer. The low-voltage device was fabricated using high-k dielectric, P(VDF-TrFE) and P(VDF-TrFE-CTFE), and the carrier mobility of PDTDP was reached 0.1 cm² V⁻¹ s⁻¹ at V_d = −5 V. PDTDP complementary inverters were fabricated, and the high ambipolar characteristics of the polymer resulted in an output voltage gain of more than 25.     

Electric conduction of PbBr-based layered perovskite organic–inorganic superlattice having carbazole chromophore-linked ammonium molecule as an organic layer

We have successfully prepared thin films of PbBr-based layered perovskite having hole-transporting carbazole chromophore-linked ammonium molecules as an organic layer by a simple spin-coating from the N,N-dimethylformamide solution in which the stoichiometric amount of lead bromide and carbazole-linked ammonium bromides was dissolved. Their X-ray diffraction profiles exhibited that their layer structure formed (0 0 n)-orientation, where c-axis is perpendicular to the substrate plane. Their layer structure depended on the alkyl chain length of ammonium molecules. When methylene length of C₅H₁₀ was employed in the carbazole-linked ammonium molecules, highest orderliness of the layer structure was attained; higher-order X-ray diffraction peaks were observed in the layered perovskite films. In the layered pervskite film, in-plane conduction, namely conduction in the direction of the stacking of carbazole chromophore, was measured. For comparison, conductivity of poly(N-vinylcarbazole) (PVCBz) thin film was also measured. The conductivity of the layered perovskite thin film (1.8 × 10^?10 Scm^?1 at 303 K) was about three order of magnitude larger than that of the PVCBz thin film (5.3 × 10^?14 Scm^?1 at 303 K). Despite the much higher conductivity of the layered peroskite thin film, the activation energy of the conductivity of the layered perovskite thin film (1.44 eV) was about 2.4 times larger than that of the PVCBz thin film (0.61 eV). This phenomenon is probably due to difference in film morphology through considering the results of AFM observation.     

Favorable basic cells for hybrid DC–DC converters

<正>With the surging demands for extremely high current at sub-1 V supply voltage level in high performance computing and autonomous driving, high density power delivery becomes one of the critical limiting factors for system integration. 48 V power bus system is emerging for these high current applications to reduce the IR losses on the power delivery networks. Thus,     

Megahertz-class printed high mobility organic thin-film transistors and inverters on plastic using attoliter-scale high-speed gravure-printed sub-5 μm gate electrodes

High performance organic thin-film transistors and inverters operating at MHz frequencies at 10 V are fabricated on plastic with high throughput (printing speed up to 1.0 m/s) using attoliter-scale high-speed gravure printing. The high performance of the devices is achieved using highly scaled gravure printed features (smaller than 5 μm) and optimizing a high mobility organic semiconductor for the short-channel gravure printed devices (>0.5 cm²/V s) to realize record performance levels.