Solution-Processed Ultralow Voltage Organic Transistors with Sharp Switching for Adaptive Visual Perception.

Neuromorphic visual systems can emulate biological retinal systems to perceive visual information under different levels of illumination, making them considerable potential for future intelligent vehicles and vision automation. However, the complex circuits and high operating voltages of conventional artificial vision systems present great challenges for device integration and power consumption. Here, we report bioinspired synaptic transistors based on organic single crystal phototransistors, which exhibit excitation and inhibition synaptic plasticity with time-varying. By manipulating the charge dynamics of the trapping centers of organic crystal-electret vertical stacks, organic transistors can operate below 1 V with record high on/off ratios close to 108 and sharp switching with a subthreshold swing of 59.8 mV dec-1. Moreover, the approach offers visual adaptation with highly localized modulation and over 98.2% recognition accuracy under different illumination levels. These bioinspired visual adaptation transistors offer great potential for simplifying the circuitry of artificial vision systems and will contribute to the development of machine vision applications. This article is protected by copyright. All rights reserved.

Stepwise Aggregation Control of PEDOT:PSS Enabled High-Conductivity, High-Resolution Printing of Polymer Electrodes for Transparent Organic Phototransistors.

Electrohydrodynamic (EHD) jet printing is a widely employed technology to create high-resolution patterns and thus has enormous potential for circuit production. However, achieving both high conductivity and high resolution in printed polymer electrodes is a challenging task. Here, by modulating the aggregation state of the conducting polymer in the solution and solid phases, a stable and continuous jetting of PEDOT:PSS is realized, and high-conductivity electrode arrays are prepared. The line width reaches less than 5 µm with a record-high conductivity of 1250 S/cm. Organic field-effect transistors (OFETs) are further developed by combining printed source/drain electrodes with ultrathin organic semiconductor crystals. These OFETs show great light sensitivity, with a specific detectivity (D*) value of 2.86 × 1014 Jones. In addition, a proof-of-concept fully transparent phototransistor is demonstrated, which opens up new pathways to multidimensional optical imaging.

Electronic Metal-Support Interactions Boost *OOH Intermediate Generation in Cu/In2Se3 for Electrochemical H2O2 Production.

Two-electron oxygen reduction reaction (2e- ORR) is a promising method for the synthesis of hydrogen peroxide (H2O2). However, high energy barriers for the generation of key *OOH intermediates hinder the process of 2e- ORR. Herein, we prepared a copper-supported indium selenide catalyst (Cu/In2Se3) to enhance the selectivity and yield of 2e- ORR by employing an electronic metal-support interactions (EMSIs) strategy. EMSIs-induced charge rearrangement between metallic Cu and In2Se3 is conducive to *OOH intermediate generation, promoting H2O2 production. Theoretical investigations reveal that the inclusion of Cu significantly lowers the energy barrier of the 2e- ORR intermediate and impedes the 4e- ORR pathway, thus favoring the formation of H2O2. The concentration of H2O2 produced by Cu/In2Se3 is ~2 times than In2Se3, and Cu/In2Se3 shows promising applications in antibiotic degradation. This research presents a valuable approach for the future utilization of EMSIs in 2e- ORR.

Enzyme-mimic catalytic activities and biomedical applications of noble metal nanoclusters.

Noble metal (e.g., Au and Ag) nanoclusters (NCs), which exhibit structural complexity and hierarchy comparable to those of natural proteins, have been increasingly pursued in artificial enzyme research. The protein-like structure of metal NCs not only ensures enzyme-mimic catalytic activity, including peroxidase-, catalase-, and superoxide dismutase-mimic activities, but also affords an unprecedented opportunity to correlate the catalytic performance with the cluster structure at the molecular or atomic levels. In this review, we aim to summarize the recent progress in programming and demystify the enzyme-mimic catalytic activity of metal NCs, presenting the state-of-the-art understandings of the structure-property relationship of metal NC-based artificial enzymes. By leveraging on a concise anatomy of the hierarchical structure of noble metal NCs, we manage to unravel the structural origin of the catalytic performance of metal NCs. Noteworthily, it has been proven that the surface ligands and metal-ligand interface of metal NCs are instrumental in influencing enzyme-mimic catalytic activities. In addition to the structure-property correlation, we also discuss the synthetic methodologies feasible to tailoring the cluster structure at the atomic level. Prior to the closure of this review with our perspectives in noble metal NC-based artificial enzymes, we also exemplify the biomedical applications based on the enzyme-mimic catalysis of metal NCs with the theranostics of kidney injury, brain inflammation, and tumors. The fundamental and methodological advancements delineated in this review would be conducive to further development of metal NCs as an alternative family of artificial enzymes.

Metal-Organic Framework-Based Hetero-Phase Nanostructure Photocatalysts with Molecular-Scale Tunable Energy Levels.

As an effective method to modulate the physicochemical properties of materials, crystal phase engineering, especially hetero-phase, plays an important role in developing high-performance photocatalysts. However, it is still a huge challenge but significant to construct porous hetero-phase nanostructures with adjustable band structures. As a kind of unique porous crystalline materials, metal-organic frameworks (MOFs) might be the appropriate candidate, but the MOF-based hetero-phase is rarely reported. Herein, we developed a secondary building unit (SBU) regulating strategy to prepare two crystal phases of Ti-MOFs constructed by titanium and 1,4-dicarboxybenzene, i.e., COK and MIL-125. Besides, COK/MIL-125 hetero-phase was further constructed. In the photocatalytic hydrogen evolution reaction, COK/MIL-125 possessed the highest H2 yield compared to COK and MIL-125, ascribing to the Z-Scheme homojunction at hetero-phase interface. Furthermore, by decorating with amino groups (i.e., NH2-COK/NH2-MIL-125), the light absorbing capacity was broadened to visible-light region, and the visible-light-driven H2 yield was greatly improved. Briefly, the MOF-based hetero-phase possesses periodic channel structures and molecularly adjustable band structures, which is scarce in traditional organic or inorganic materials. As a proof of concept, our work not only highlights the development of MOF-based hetero-phase nanostructures, but also paves a novel avenue for designing high-performance photocatalysts.

Molecularly Thin 2D Organic Single Crystals: A New Platform for High-Performance Polarization-Sensitive Phototransistors.

The inherent linear dichroism (LD), high absorption, and solution processability of organic semiconductors hold immense potential to revolutionize polarized light detection. However, the disordered molecular packing inherent to polycrystalline thin films obscures their intrinsic diattenuation, resulting in diminished polarization sensitivity. In this study, we develop filter-free organic polarization-sensitive phototransistors (PSPs) with both a high linear dichroic ratio (LDR) and exceptional photosensitivity utilizing molecularly thin dithieno[3,2-b:2',3'-d]thiophene derivatives (DTT-8) two-dimensional molecular crystals (2DMCs) as the active layer. The orderly molecular packing in 2DMCs amplifies the inherent LD, and their molecular-scale thickness enables complete channel depletion, significantly reducing the dark current. As a result, PSPs with an impressive LDR of 3.15 and a photosensitivity reaching 3.02 × 106 are obtained. These findings present a practical demonstration of using the polarization angle as an encryption key in optical communication, showcasing the potential of 2DMCs as a viable and promising category of semiconductors for filter-free, polarization-sensitive photodetectors.

Key mRNAs and lncRNAs of pituitary that affect the reproduction of FecB + + small tail han sheep.

BACKGROUND: The pituitary directly regulates the reproductive process through follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Transcriptomic research on the pituitaries of ewes with different FecB (fecundity Booroola) genotypes has shown that some key genes and lncRNAs play an important role in pituitary function and sheep fecundity. Our previous study found that ewes with FecB + + genotypes (without FecB mutation) still had individuals with more than one offspring per birth. It is hoped to analyze this phenomenon from the perspective of the pituitary transcriptome. RESULTS: The 12 Small Tail Han Sheep were equally divided into polytocous sheep in the follicular phase (PF), polytocous sheep in the luteal phase (PL), monotocous sheep in the follicular phase (MF), and monotocous sheep in the luteal phase (ML). Pituitary tissues were collected after estrus synchronous treatment for transcriptomic analysis. A total of 384 differentially expressed genes (DEGs) (182 in PF vs. MF and 202 in PL vs. ML) and 844 differentially expressed lncRNAs (DELs) (427 in PF vs. MF and 417 in PL vs. ML) were obtained from the polytocous-monotocous comparison groups in the two phases. Functional enrichment analysis showed that the DEGs in the two phases were enriched in signaling pathways known to play an important role in sheep fecundity, such as calcium ion binding and cAMP signaling pathways. A total of 1322 target relationship pairs (551 pairs in PF vs. MF and 771 pairs in PL vs. ML) were obtained for the target genes prediction of DELs, of which 29 DEL-DEG target relationship pairs (nine pairs in PF vs. MF and twenty pairs in PL vs. ML). In addition, the competing endogenous RNA (ceRNA) networks were constructed to explore the regulatory relationships of DEGs, and some important regulatory relationship pairs were obtained. CONCLUSION: According to the analysis results, we hypothesized that the pituitary first receives steroid hormone signals from the ovary and uterus and that VAV3 (Vav Guanine Nucleotide Exchange Factor 3), GABRG1 (Gamma-Aminobutyric Acid A Receptor, Gamma 1), and FNDC1 (Fibronectin Type III Domain Containing 1) played an important role in this process. Subsequently, the reproductive process was regulated by gonadotropins, and IGFBP1 (Insulin-like Growth Factor Binding Protein 1) was directly involved in this process, ultimately affecting litter size. In addition, TGIF1 (Transforming Growth Factor-Beta-Induced Factor 1) and TMEFF2 (Transmembrane Protein With EGF Like And Two Follistatin Like Domains 2) compensated for the effect of the FecB mutation and function by acting on TGF-ß/SMAD signaling pathway, an important pathway for sheep reproduction. These results provided a reference for understanding the mechanism of multiple births in Small Tail Han Sheep without FecB mutation.

Constructing Nano-Heterostructure with Dual-Site to Boost H2 O2 Activation and Regulate the Transformation of Free Radicals.

A major issue with Fenton-like reaction is the excessive consumption of H2 O2 caused by the sluggish regeneration rate of low-valent metal, and how to improve the activation efficiency of H2 O2 has become a key in current research. Herein, a nano-heterostructure catalyst (1.0-MnCu/C) based on nano-interface engineering is constructed by supporting Cu and MnO on carbon skeleton, and its kinetic rate for the degradation of tetracycline hydrochloride is 0.0436 min-1 , which is 2.9 times higher than that of Cu/C system (0.0151 min-1 ). The enhancement of removal rate results from the introduced Mn species can aggregate and transfer electrons to Cu sites through the electron bridge Mn-N/O-Cu, thus preventing Cu2+ from oxidizing H2 O2 to form O2 •- , and facilitating the reduction of Cu2+ and generating more reactive oxygen species (1 O2 and ·OH) with stronger oxidation ability, resulting in H2 O2 utilization efficiency is 1.9 times as much as that of Cu/C. Additionally, the good and stable practical application capacity in different bodies demonstrates that it has great potential for practical environmental remediation.

An n-Type Conjugated Polymer with Low Crystallinity for High-Performance Organic Thermoelectrics.

Conjugated polymers (CPs) with low crystallinity are promising candidates for application in organic thermoelectrics (OTEs), particularly in flexible devices, because the disordered structures of these CPs can effectively accommodate dopants and ensure robust resistance to bending. However, n-doped CPs usually exhibit poor thermoelectric performance, which hinders the development of high-performance thermoelectric generators. Herein, we report an n-type CP (ThDPP-CNBTz) comprising two acceptor units: a thiophene-flanked diketopyrrolopyrrole and a cyano-functionalized benzothiadiazole. ThDPP-CNBTz shows a low LUMO energy level of below -4.20 eV and features low crystallinity, enabling high doping efficiency. Moreover, the dual-acceptor design enhances polaron delocalization, resulting in good thermoelectric performance. After n-doping, ThDPP-CNBTz exhibits an average electrical conductivity (σ) of 50.6 S cm-1 and a maximum power factor (PF) of 126.8 µW m-1 K-2, which is among the highest values reported for solution-processed n-type CPs to date. Additionally, a solution-processed flexible OTE device based on doped ThDPP-CNBTz exhibits a maximum PF of 70 µW m-1 K-2; the flexible device also shows remarkable resistance to bending strain, with only a marginal change in σ after 600 bending cycles. The findings presented in this work will advance the development of n-type CPs for OTE devices, and flexible devices in particular.

Achieving Zero-Temperature Coefficient Point Behavior by Defect Passivation for Temperature-Immune Organic Field-Effect Transistors.

Organic field-effect transistors (OFETs) have broad prospects in biomedical, sensor, and aerospace applications. However, obtaining temperature-immune OFETs is difficult because the electrical properties of organic semiconductors (OSCs) are temperature-sensitive. The zero-temperature coefficient (ZTC) point behavior can be used to achieve a temperature-immune output current; however, it is difficult to achieve in organic devices with thermal activation characteristics, according to the existing ZTC point theory. Here, the Fermi pinning in OSCs is eliminated using the defect passivation strategy, making the Fermi level closer to the tail state at low temperatures; thus threshold voltage (VT) is negatively correlated with temperature. ZTC point behaviors in OFETs are achieved by compensation between VT and mobility at different temperatures to improve its temperature immunity. A temperature-immune output current can be realized in a variable-temperature bias voltage test over 50000 s by biasing the device at the ZTC point. This study provides an effective solution for temperature-immune OFETs and inspiration for their practical application.

Large-Area Conductive MOF Ultrathin Film Controllably Integrating Dinuclear-Metal Sites and Photosensitizers to Boost Photocatalytic CO2 Reduction with H2O as an Electron Donor.

Owing to the electrical conductivity and periodic porosity, conductive metal-organic framework (cMOF) ultrathin films open new perspectives to photocatalysis. The space-selective assembly of catalytic sites and photosensitizers in/on cMOF is favorable for promoting the separation of photogenerated carriers and mass transfer. However, the controllable integration of functional units into the cMOF film is rarely reported. Herein, via the synergistic effect of steric hindrance and an electrostatic-driven strategy, the dinuclear-metal molecular catalysts (DMC) and perovskite (PVK) quantum dot photosensitizers were immobilized into channels and onto the surface of cMOF ultrathin films, respectively, affording [DMC@cMOF]-PVK film photocatalysts. In this unique heterostructure, cMOF not only facilitated the charge transfer from PVK to DMC but also guaranteed mass transfer. Using H2O as an electron donor, [DMC@cMOF]-PVK realized a 133.36 µmol·g-1·h-1 CO yield in photocatalytic CO2 reduction, much higher than PVK and DMC-PVK. Owing to the excellent light transmission of films, multilayers of [DMC@cMOF]-PVK were integrated to increase the CO yield per unit area, and the 10-layer device realized a 1115.92 µmol·m-2 CO yield in 4 h, which was 8-fold higher than that of powder counterpart. This work not only lightens the development of cMOF-based composite films but also paves a novel avenue for an ultrathin film photocatalyst.

Inorganic Halide Perovskite Nanowires/Conjugated Polymer Heterojunction-Based Optoelectronic Synaptic Transistors for Dynamic Machine Vision.

Inspired by the retina, artificial optoelectronic synapses have groundbreaking potential for machine vision. The field-effect transistor is a crucial platform for optoelectronic synapses that is highly sensitive to external stimuli and can modulate conductivity. On the basis of the decent optical absorption, perovskite materials have been widely employed for constructing optoelectronic synaptic transistors. However, the reported optoelectronic synaptic transistors focus on the static processing of independent stimuli at different moments, while the natural visual information consists of temporal signals. Here, we report CsPbBrI2 nanowire-based optoelectronic synaptic transistors to study the dynamic responses of artificial synaptic transistors to time-varying visual information for the first time. Moreover, on the basis of the dynamic synaptic behavior, a hardware system with an accuracy of 85% is built to the trajectory of moving objects. This work offers a new way to develop artificial optoelectronic synapses for the construction of dynamic machine vision systems.

Universal Design and Efficient Synthesis for High Ambipolar Mobility Emissive Conjugated Polymers.

High ambipolar mobility emissive conjugated polymers (HAME-CPs) are perfect candidates for organic optoelectronic devices, such as polymer light emitting transistors. However, due to intrinsic trade-off relationship between high ambipolar mobility and strong solid-state luminescence, the development of HAME-CPs suffers from high structural and synthetic complexity. Herein, a universal design principle and simple synthetic approach for HAME-CPs are developed. A series of simple non-fused polymers composed of charge transfer units, π bridges and emissive units are synthesized via a two-step microwave assisted C-H arylation and direct arylation polymerization protocol with high total yields up to 61 %. The synthetic protocol is verified valid among 7 monomers and 8 polymers. Most importantly, all 8 conjugated polymers have strong solid-state emission with high photoluminescence quantum yields up to 24 %. Furthermore, 4 polymers exhibit high ambipolar field effect mobility up to 10-2 cm2 V-1 s-1, and can be used in multifunctional optoelectronic devices. This work opens a new avenue for developing HAME-CPs by efficient synthesis and rational design.

Overcoming the Unfavorable Effects of "Boltzmann Tyranny:" Ultra-Low Subthreshold Swing in Organic Phototransistors via One-Transistor-One-Memristor Architecture.

Organic phototransistors (OPTs), as photosensitive organic field-effect transistors (OFETs), have gained significant attention due to their pivotal roles in imaging, optical communication, and night vision. However, their performance is fundamentally limited by the Boltzmann distribution of charge carriers, which constrains the average subthreshold swing (SSave ) to a minimum of 60 mV/decade at room temperature. In this study, an innovative one-transistor-one-memristor (1T1R) architecture is proposed to overcome the Boltzmann limit in conventional OFETs. By replacing the source electrode in an OFET with a memristor, the 1T1R device exploits the memristor's sharp resistance state transitions to achieve an ultra-low SSave of 18 mV/decade. Consequently, the 1T1R devices demonstrate remarkable sensitivity to photo illumination, with a high specific detectivity of 3.9 × 109  cm W-1 Hz1/2 , outperforming conventional OPTs (4.9 × 104  cm W-1 Hz1/2 ) by more than four orders of magnitude. The 1T1R architecture presents a potentially universal solution for overcoming the detrimental effects of "Boltzmann tyranny," setting the stage for the development of ultra-low SSave devices in various optoelectronic applications.

Recent progress in emerging two-dimensional organic-inorganic van der Waals heterojunctions.

Two-dimensional (2D) materials have attracted significant attention in recent decades due to their exceptional optoelectronic properties. Among them, to meet the growing demand for multifunctional applications, 2D organic-inorganic van der Waals (vdW) heterojunctions have become increasingly popular in the development of optoelectronic devices. These heterojunctions demonstrate impressive capability to synergistically combine the favourable characteristics of organic and inorganic materials, thereby offering a wide range of advantages. Also, they enable the creation of innovative device structures and introduce novel functionalities in existing 2D materials, avoiding the need for lattice matching in different material systems. Presently, researchers are actively working on improving the performance of devices based on 2D organic-inorganic vdW heterojunctions by focusing on enhancing the quality of 2D materials, precise stacking methods, energy band regulation, and material selection. Therefore, this review presents a thorough examination of the emerging 2D organic-inorganic vdW heterojunctions, including their classification, fabrication, and corresponding devices. Additionally, this review offers profound and comprehensive insight into the challenges in this field to inspire future research directions. It is expected to propel researchers to harness the extraordinary capabilities of 2D organic-inorganic vdW heterojunctions for a wider range of applications by further advancing the understanding of their fundamental properties, expanding the range of available materials, and exploring novel device architectures. The ongoing research and development in this field hold potential to unlock captivating advancements and foster practical applications across diverse industries.

Phase and Composition Engineering of Self-Intercalated 2D Metallic Tantalum Sulfide for Second-Harmonic Generation.

Self-intercalation in two-dimensional (2D) materials is significant, as it offers a versatile approach to modify material properties, enabling the creation of interesting functional materials, which is essential in advancing applications across various fields. Here, we define ic-2D materials as covalently bonded compounds that result from the self-intercalation of a metal into layered 2D compounds. However, precisely growing ic-2D materials with controllable phases and self-intercalation concentrations to fully exploit the applications in the ic-2D family remains a great challenge. Herein, we demonstrated the controlled synthesis of self-intercalated H-phase and T-phase Ta1+xS2 via a temperature-driven chemical vapor deposition (CVD) approach with a viable intercalation concentration spanning from 10% to 58%. Atomic-resolution scanning transmission electron microscopy-annular dark field imaging demonstrated that the self-intercalated Ta atoms occupy the octahedral vacancies located at the van der Waals gap. The nonperiodic Ta atoms break the centrosymmetry structure and Fermi surface properties of intrinsic TaS2. Therefore, ic-2D T-phase Ta1+xS2 consistently exhibit a spontaneous nonlinear optical (NLO) effect regardless of the sample thickness and self-intercalation concentrations. Our results propose an approach to activate the NLO response of centrosymmetric 2D materials, achieving the modulation of a wide range of optoelectronic properties via nonperiodic self-intercalation in the ic-2D family.

Unraveling the crucial role of trace oxygen in organic semiconductors.

Optoelectronic properties of semiconductors are significantly modified by impurities at trace level. Oxygen, a prevalent impurity in organic semiconductors (OSCs), has long been considered charge-carrier traps, leading to mobility degradation and stability problems. However, this understanding relies on the conventional deoxygenation methods, by which oxygen residues in OSCs are inevitable. It implies that the current understanding is questionable. Here, we develop a non-destructive deoxygenation method (i.e., de-doping) for OSCs by a soft plasma treatment, and thus reveal that trace oxygen significantly pre-empties the donor-like traps in OSCs, which is the origin of p-type characteristics exhibited by the majority of these materials. This insight is completely opposite to the previously reported carrier trapping and can clarify some previously unexplained organic electronics phenomena. Furthermore, the de-doping results in the disappearance of p-type behaviors and significant increase of n-type properties, while re-doping (under light irradiation in O2) can controllably reverse the process. Benefiting from this, the key electronic characteristics (e.g., polarity, conductivity, threshold voltage, and mobility) can be precisely modulated in a nondestructive way, expanding the explorable property space for all known OSC materials.

Frequency-Dependent Multistep Ferroelectric Polarization Switching Mechanism in P(VDF-TrFE)-Based Capacitors Induced by Polystyrene Electret-like Modulation.

In this work, we investigate multistep ferroelectric polarization switching dynamics of a series of poly(vinylidene fluoride-trifluoroethylene)/polystyrene, P(VDF-TrFE)/PS, as active layers in ferroelectric capacitors with variable P(VDF-TrFE)/PS thickness ratios and a wide range of driving voltage frequencies (1-1000 Hz). The PS electret-like modulation effects on the depolarized field fluctuation are proven to be responsible for this multistep ferroelectric polarization switching process. To be specific, the switching current density peak splits into two peaks in both positive and negative voltage ranges according to the stimulus-response (S-R) data from the metal-ferroelectric-electret-metal capacitor driven by a periodic triangular voltage wave. The double-peak current trough appears when the transitorily suppressed ferroelectric polarization switching occurs while the discharge and recharge of the PS electret by external voltage brings a specific dynamic change in the electric field across ferroelectric (EFE). We also propose a theoretical model to simulate the ferroelectric polarization switching process at a current trough zone. This phenomenon provides new concepts on the electret-modulated multistep ferroelectric switching dynamics, and such switching mechanisms are critical for realizing reliable nonvolatile memory applications in flexible electronics.

High Mobility Emissive Excimer Organic Semiconductor Towards Color-Tunable Light-Emitting Transistors.

Organic light-emitting transistors (OLETs) are highly integrated and minimized optoelectronic devices with significant potential superiority in smart displays and optical communications. To realize these various applications, it is urgently needed for color-tunable emission in OLETs, but remains a great challenge as a result of the difficulty for designing organic semiconductors simultaneously integrating high carrier mobility, strong solid-state emission, and the ability for potential tunable colors. Herein, a high mobility emissive excimer organic semiconductor, 2,7-di(2-anthryl)-9H-fluorene (2,7-DAF) was reasonably designed by introducing a rotatable carbon-carbon single bond connecting two anthracene groups at the 2,7-sites of fluorene, and the small torsion angles simultaneously guarantee effective conjugation and suppress fluorescence quenching. Indeed, the unique stable dimer arrangement and herringbone packing mode of 2,7-DAF single crystal enables its superior integrated optoelectronic properties with high carrier mobility of 2.16 cm2 ⋅ V-1 ⋅ s-1 , and strong excimer emission with absolute photoluminescence quantum yield (PLQY) of 47.4 %. Furthermore, the voltage-dependent electrically induced color-tunable emission from orange to blue was also demonstrated for an individual 2,7-DAF single crystal based OLETs for the first time. This work opens the door for a new class of high mobility emissive excimer organic semiconductors, and provides a good platform for the study of color-tunable OLETs.