Performance Of Organic Field-effect Transistors Research Articles

Evaluating the performance of p-type organic field-effect transistor using different source–drain electrodes

Evaluating the performance of p-type organic field-effect transistor using different source–drain electrodes

Detailed Investigation of Plasticized PMMA Dielectric for Improved Performance of Organic Field-Effect Transistors

Detailed Investigation of Plasticized PMMA Dielectric for Improved Performance of Organic Field-Effect Transistors

Enhanced N-type Semiconducting Performance of Asymmetric Monochlorinated Isoindigo-based Semiregioregular Polymers under Dynamic Forces.

The asymmetric monochlorination strategy not only effectively addresses the steric issues in conventional dichlorination but also enables the development of promising acceptor units and semiregioregular polymers. Herein, monochlorinated isoindigo (1CIID) is successfully designed and synthesized by selectively introducing single chlorine (Cl) atoms. Furthermore, the 1CIID copolymerizes with two donor counterparts, centrosymmetric 2,2'-bithiophene (2T) and axisymmetric 4,7-di(thiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT), forming two polymers, P1CIID-2T and P1CIID-DTBT. These polymers exhibit notable differences in backbone linearity and dipole moments, influenced by the symmetry of their donor counterparts. In particular, P1CIID-2T, which contains a centrosymmetric 2T unit, demonstrates a linear backbone and a significant dipole moment of 10.20 D. These properties contribute to the favorable film morphology of P1CIID-2T, characterized by highly ordered crystallinity in the presence of fifth-order (500) X-ray diffraction peaks. Notably, P1CIID-2T exhibits a significant improvement in molecular alignment under dynamic force, resulting in over 8-fold improvement in the performance of organic field-effect transistor (OFET) devices, with superior electron mobility up to 1.22 cm2 V-1 s-1. This study represents the first synthesis of asymmetric monochlorinated isoindigo-based conjugated polymers, highlighting the potential of asymmetric monochlorination for developing n-type semiconducting polymers. Moreover, our findings provide valuable insights into the relationship between the molecular structure and properties.

Hole Mobility Enhancement in Benzo[1,2-b:4,5-b']Dithiophene-Based Conjugated Polymer Transistors through Directional Alignment, Perovskite Functionalization and Solid-State Electrolyte Gating.

Tunability in electronic and optical properties has been intensively explored for developing conjugated polymers and their applications in organic and perovskite-based electronics. Particularly, the charge carrier mobility of conjugatedpolymer semiconductors has been deemed to be a vital figure-of-merit for achieving high-performance organic field-effect transistors (OFETs). In this study, the systematic hole carrier mobility improvement of benzo[1,2-b:4,5-b']dithiophene-based conjugated polymer in perovskite-functionalized organic transistors is demonstrated. In conventional OFETs with a poly(methyl methacrylate) (PMMA)gate dielectric, improvements in hole mobility of 0.019cm2V-1s-1 are measured using an off-center spin-coating technique, which exceeds those of on-center counterparts (0.22 ± 0.07 × 10-2cm2V-1s-1). Furthermore, the mobility drastically increases by adopting solid-state electrolyte gating, corresponding to 2.99 ± 1.03cm2V-1s-1 for the control, and the best hole mobility is 8.03cm2V-1s-1 (average ≈ 6.94 ± 0.59cm2V-1s-1) for perovskite-functionalized OFETs with a high current on/off ratio of >106. The achieved device performance would be attributed to the enhanced film crystallinity and charge carrier density in the hybrid perovskite-functionalized organic transistor channel, resulting from the high-capacitance electrolyte dielectric.

Solution-processable quinoidal compounds containing heterocycle for air-stable n‑type organic field-effect transistors and gas sensors

Organic field effect transistors (OFETs) have potential applications in gas sensing area, but the performance and diversity of n-type OFETs are still far behind that of p-type OFETs due to the poor stability in air atmosphere. Herein, a series of novel dicyanomethylene-terminated quinoids compounds were synthesized and characterized by using electron withdrawing aromatic heterocycles as the core structural units. The introduction of alkyl branch chain greatly improves the solubility, which is helpful to the preparation of thin film OFETs devices by low-cost solution method. These OFETs show typical n-channel FET characteristics with mobility ranging from 10−3∼10−1 cm2V−1s−1. Among them, the 3-T-TZCN based OFETs exhibit the best stability, in which the mobility decreased no more than 18 % after 90 days stored in air atmosphere, this is an outstanding performance compared with the previous researches. We further investigated the dimethyl methylphosphonate (DMMP, which is a substitute for detecting sarin) gas sensing performance of each material, the experimental results indicated that the sensitivity, recovery and stability of 3-T-TZCN are better than other materials, and the limit of detection can be lower to 10 ppb level. This general approach could offer new solution for constructing n-type OFET-based gas sensors with good stability in air atmosphere.

Diselenophene-Dithioalkylthiophene Based Quinoidal Small Molecules for Ambipolar Organic Field Effect Transistors.

This work presents a series of novel quinoidal organic semiconductors based on diselenophene-dithioalkylthiophene (DSpDST) conjugated cores with various side-chain lengths (-thiohexyl, -thiodecyl, and -thiotetradecyl, designated DSpDSTQ-6, DSpDSTQ-10, and DSpDSTQ-14, respectively). The purpose of this research is to develop solution-processable organic semiconductors using dicyanomethylene end-capped organic small molecules for organic field effect transistors (OFETs) application. The physical, electrochemical, and electrical properties of these new DSpDSTQs are systematically studied, along with their performance in OFETs and thin film morphologies. Additionally, the molecular structures of DSpDSTQ are determined through density functional theory (DFT) calculations and single-crystal X-ray diffraction analysis. The results reveal the presence of intramolecular S (alkyl)···Se (selenophene) interactions, which result in a planar SR-containing DSpDSTQ core, thereby promoting extended π-orbital interactions and efficient charge transport in the OFETs. Moreover, the influence of thioalkyl side chain length on surface morphologies and microstructures is investigated. Remarkably, the compound with the shortest thioalkyl chain, DSpDSTQ-6, demonstrates ambipolar carrier transport with the highest electron and hole mobilities of 0.334 and 0.463 cm2 V-1 s-1 , respectively. These findings highlight the excellence of ambipolar characteristics of solution-processable OFETs based on DSpDSTQs even under ambient conditions.

Advancing organic electronics: Achieving reliable synthesis of conjugated polymers with various carrier polarities using a continuous flow reactor

Donor-acceptor (D-A) conjugated polymers often exhibit excellent performance in electronic and photonic applications, however, their synthesis remains a hurdle to achieving their wide-spread commercialization. While scalable and reproducible flow syntheses have emerged as promising candidates to address this issue, they have only been applied to a narrow scope of polymer types. In this study, we explore the synthesis of six different D-A conjugated polymers in a continuous flow reactor to determine how reaction and polymer parameters influence the degree of polymerization (DP) and quality of the resulting polymers. We found that we could successfully synthesize p-type, n-type, and ambipolar D-A conjugated polymers with a single set of reaction parameters. Only the reaction time required optimization to achieve high-DPs. Importantly, we found that we could achieve comparable DPs to batch reactions, but with higher yields and much shorter reaction times. High-quality polymers were also obtained, which was confirmed with optical and electrochemical properties measurements and by their performance in organic field-effect transistors. We expect this work to further establish flow synthesis as an ideal method to make D-A conjugated polymers, which may help facilitate their commercialization in high-performing organic devices.

Towards sustainable, solution-processed organic field-effect transistors using cashew gum as the gate dielectric

To realize low-cost, environmentally friendly electronic devices and circuits, there is currently a strong trend to explore plant-based dielectric materials because they can be responsibly sourced from agricultural or forest vegetation, are generally water-soluble, and possess good electrical insulator properties. In this contribution, organic field-effect transistors (OFETs) using a biopolymer dielectric obtained from exudates of Anacardium occidentale Linn. trees, namely, cashew gum (CG), are reported. To characterise the physical and dielectric properties of the gum, thin films and metal-insulator-metal (MIM) capacitors were prepared and characterized. To evaluate the material’s performance in OFETs, bottom-gate top-contact (BGTC) p-channel poly [3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo (3,4-c)pyrrole-1,4-dione) thieno (3,2-b) thiophene]:polymethyl methacrylate (DPPTTT:PMMA) transistors were engineered and studied. The fabricated MIM capacitors display a comparatively high areal capacitance of 260 nF/cm2 at 1 kHz for 130 nm thick films. As a result, the solution-processed DPPTTT:PMMA OFETs favourably operate at 3 V with the average saturation field-effect mobility equal to 0.20 cm2/Vs., threshold voltage around −1.4 V, subthreshold swing in the region of 250 mV/dec, and ON/OFF current ratio well above 103. As such, cashew gum emerges as a promising dielectric for sustainable manufacturing of solution-processed organic FETs.

Enhancing Gating Performance in Organic Molecular Field-Effect Transistors by Introducing Polar Azulene Components.

Organic molecular field-effect transistors (FETs) are promising building components for future electronic circuits. Efficient control of charge transport properties is one key issue in the design of organic molecular FETs. In this study, we propose a redesign of a naphthalene-based FET by introducing two azulene components in opposite dipole moment directions. Using density functional theory combined with non-equilibrium Green's function, the simulated electronic transport characteristics reveal that the introduction of polar azulene components effectively narrows the frontier molecular orbitals gap, leading to an increase in the ON-state current. Meanwhile, the OFF-state current is significantly suppressed by highly localizing the dominant electronic transport channel. As a result, improved gate controllability is achieved with a higher ON-OFF current ratio, which is nearly seven times higher than that of the naphthalene-based FET device. These findings provide theoretical directions for future design of organic molecular FET devices with enhanced gating regulation efficiency.

Molecular Design Concept for Enhancement Charge Carrier Mobility in OFETs: A Review.

In the last two decades, organic field-effect transistors (OFETs) have garnered increasing attention from the scientific and industrial communities. The performance of OFETs can be evaluated based on three factors: the charge transport mobility (μ), threshold voltage (Vth), and current on/off ratio (Ion/off). To enhance μ, numerous studies have concentrated on optimizing charge transport within the semiconductor layer. These efforts include: (i) extending π-conjugation, enhancing molecular planarity, and optimizing donor-acceptor structures to improve charge transport within individual molecules; and (ii) promoting strong aggregation, achieving well-ordered structures, and reducing molecular distances to enhance charge transport between molecules. In order to obtain a high charge transport mobility, the charge injection from the electrodes into the semiconductor layer is also important. Since a suitable frontier molecular orbitals' level could align with the work function of the electrodes, in turn forming an Ohmic contact at the interface. OFETs are classified into p-type (hole transport), n-type (electron transport), and ambipolar-type (both hole and electron transport) based on their charge transport characteristics. As of now, the majority of reported conjugated materials are of the p-type semiconductor category, with research on n-type or ambipolar conjugated materials lagging significantly behind. This review introduces the molecular design concept for enhancing charge carrier mobility, addressing both within the semiconductor layer and charge injection aspects. Additionally, the process of designing or converting the semiconductor type is summarized. Lastly, this review discusses potential trends in evolution and challenges and provides an outlook; the ultimate objective is to outline a theoretical framework for designing high-performance organic semiconductors that can advance the development of OFET applications.

Improving the mobility of D-A polymer PTB7-Th thin film field-effect transistors through organic salt doping

Organic salt doping is an effective method to control the electrical properties of organic semiconductor materials, while its underlying mechanism remains to be studied. In this work, we report the improvement of organic field-effect transistor (OFET) performance by doping the D-A polymer semiconductor PTB7-Th with organic salts. The underlying mechanism of PTB7-Th's organic salt doping in OFETs has been explored to fill the existing research gap. The doping of organic salts can improve the hole mobility of the device and change the threshold voltage. In addition, at low doping ratios, the on-off ratio of the device is not sacrificed but remains unchanged. Finally, we have made a series of characterizations of the properties of doped polymers through absorption, EPR, and UPS, which provide specific guidelines for modifying D-A polymer devices.

Novel Frequency Dependent OFET Attenuator Using ClInPc with Al2O3 Embedded Nanoparticles in Nylon 11 for Flexible Electronics

The Organic field-effect transistors (OFETs) have been largely investigated due to their low-cost manufacturing, flexibility, and lightweight, as well as their optical and electrical characteristics. That allow its application in sensors, amplifiers, attenuators signal filtering, and high-frequency response devices, like biosensing, wearable electronics, optoelectronics, telecommunications, and other potential applications. Throughout this investigation, a ClInPc flexible OFET with Al2O3 embedded particles in nylon 11, was manufactured and characterized to evaluate the optoelectronic and morphological properties. For the manufacturing, a high-vacuum thermal evaporation deposition technique was used, and UV-vis spectroscopy analysis and scanning electron microscopy were conducted to evaluate the optoelectronic and morphological properties. Also, a study regarding the electrical characteristics for different time-dependent wavefunction input signals, changing the input voltage and frequency, has been conducted. The latter was driven to determine the time-response characteristics, gains, phase shift and to determine whether the device function as an attenuator or an amplifier with the selected configuration. The device has been modelled to obtain the OFET operation parameters. A resulting capacitance of 567 pF was calculated. Uniform and continuous films where obtained, which guarantees an efficient charge transport. For all signals the output voltage is lower than that of the input voltage. Also, for the higher frequency the output voltage is decreased compared to lower frequencies. Gains decreasing variation of up to 0.05 indicate the operating application as an attenuator. Phase variation of up to 100 °, resulted while varying the input frequency. The model resulted on a gate capacitance value between 500 and 1180 pF, and gate-drain capacitance value between 50 and 500 pF. All of this could give evidence that state of the art ClInPc flexible OFET device with Al2O3 embedded nanoparticles in nylon 11 could be used toward current high-performance frequency-dependent flexible applications.

(Invited) Making Stacks of Nitrogenated Polycyclic Aromatic Hydrocarbons with Hydrogen Bonds

Architectures constituted of stacked aromatics play a crucial role in the development of function in biomacromolecules. Recreating this feature on synthetic systems would not only allow understanding and reproducing biological functions but also developing new functions. For instance, the performance of organic field-effect transistors, light-emitting diodes, and solar cells critically depends on the charge transport efficiency of stacks of organic semiconductors. Among different packing configurations, lamellar π-stacking has been identified as an optimal configuration for electronic transport, because of the efficient intermolecular electronic coupling.Nitrogenated polycyclic aromatic hydrocarbons and nanographenes have attracted considerable attention in recent years. Besides the effect of nitrogen doping on the electronic structure, sp2 nitrogens can be engaged in hydrogen bonding interactions as acceptors. We have developed the synthesis of novel architectures constituted of stacked nitrogenated polycyclic aromatic hydrocarbons held together by hydrogen bonds, which include new families of pseudorotaxanes, rotaxanes, foldamers and supramolecular polymers. The synthesis and self-assembling properties of these systems will be discussed together with their charge transporting properties.

Simulation study of various factors affecting the performance of vertical organic field-effect transistors

Abstract Vertical organic field-effect transistors (VOFETs) can offer a short channel architecture that can further enhance the performance at low operating voltages, which makes it more viable for organic electronics applications. VOFETs can be prepared using low-cost techniques that reduce the high processing costs and can operate at high current densities and relatively high fRequencies. To further improve the performance, high current density, and operating frequency, the physics of charge carrier transport should be understood well with the simulation. The main problem with VOFET is the high off-current which is inevitable due to conduction from the source to the drain contact. Many efforts have been made to reduce the off-state current by the addition of an insulating layer on top of the source electrode, which further increases the processing complexity and cost of fabrication. Simulations based on device geometry, contact barriers, and organic semiconductor parameters are carried out to study the charge carrier transport in VOFET. The simulation results show that the most important factor, to enhance the performance is the device geometry or architecture, which requires a specific fill factor, a ratio of the exposed gate dielectric width to the total width of the device with the source electrode. The simulation results also show a different type of working physics of the basic VOFET architecture where the On/Off ratio and subthreshold swing are largely dependent on the initial negative gate field instead of the accumulated charge carriers at positive gate fields. Optimized VOFET architecture is then simulated for variation in contact barrier and semiconductor properties, which show further enhancement in performance.

Solution-Processable Indenofluorenes on Polymer Brush Interlayer: Remarkable N-Channel Field-Effect Transistor Characteristics under Ambient Conditions.

The development of solution-processable n-type molecular semiconductors that exhibit high electron mobility (μe ≥ 0.5 cm2/(V·s)) under ambient conditions, along with high current modulation (Ion/Ioff ≥ 106-107) and near-zero turn on voltage (Von) characteristics, has lagged behind that of other semiconductors in organic field-effect transistors (OFETs). Here, we report the design, synthesis, physicochemical and optoelectronic characterizations, and OFET performances of a library of solution-processable, low-LUMO (-4.20 eV) 2,2'-(2,8-bis(3-alkylthiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile small molecules, β,β'-Cn-TIFDMTs, having varied alkyl chain lengths (n = 8, 12, 16). An intriguing correlation is identified between the solid-isotropic liquid transition enthalpies and the solubilities, indicating that cohesive energetics, which are tuned by alkyl chains, play a pivotal role in determining solubility. The semiconductors were spin-coated under ambient conditions on densely packed (grafting densities of 0.19-0.45 chains/nm2) ultrathin (∼3.6-6.6 nm) polystyrene-brush surfaces. It is demonstrated that, on this polymer interlayer, thermally induced dispersive interactions occurring over a large number of methylene units between flexible alkyl chains (i.e., zipper effect) are critical to achieve a favorable thin-film crystallization with a proper microstructure and morphology for efficient charge transport. While C8 and C16 chains show a minimal zipper effect upon thermal annealing, C12 chains undergo an extended interdigitation involving ∼6 methylene units. This results in the formation of large crystallites having lamellar stacking ((100) coherence length ∼30 nm) in the out-of-plane direction and highly favorable in-plane π-interactions in a slipped-stacked arrangement. Uninterrupted microstructural integrity (i.e., no face-on (010)-oriented crystallites) was found to be critical to achieving high mobilities. The excellent crystallinity of the C12-substituted semiconductor thin film was also evident in the observed crystal lattice vibrations (phonons) at 58 cm-1 in low-frequency Raman scattering. Two-dimensional micrometer-sized (∼1-3 μm), sharp-edged plate-like grains lying parallel with the substrate plane were observed. OFETs fabricated by the current small molecules showed excellent n-channel behavior in ambient with μe values reaching ∼0.9 cm2/(V·s), Ion/Ioff ∼ 107-108, and Von ≈ 0 V. Our study not only demonstrates one of the highest performing n-channel OFET devices reported under ambient conditions via solution processing but also elucidates significant relationships among chemical structures, molecular properties, self-assembly from solution into a thin film, and semiconducting thin-film properties. The design rationales presented herein may open up new avenues for the development of high-electron-mobility novel electron-deficient indenofluorene and short-axis substituted donor-acceptor π-architectures via alkyl chain engineering and interface engineering.

High Frequency Solution‐Processed Organic Field‐Effect Transistors with High‐Resolution Printed Short Channels

AbstractOrganic electronics is an emerging technology that enables the fabrication of devices with low‐cost and simple solution‐based processes at room temperature. In particular, it is an ideal candidate for the Internet of Things since devices can be easily integrated in everyday objects, potentially creating a distributed network of wireless communicating electronics. Recent efforts allowed to boost operational frequency of organic field‐effect transistors (OFETs), required to achieve efficient wireless communication. However, in the majority of cases, in order to increase the dynamic performances of OFETs, masks based lithographic techniques are used to reduce device critical dimensions, such as channel and overlap lengths. This study reports the successful integration of direct written metal contacts defining a 1.4 µm short channel, printed with ultra‐precise deposition technique (UPD), in fully solution fabricated n‐type OFETs. An average transition frequency as high as 25.5 MHz is achieved at 25 V. This result demonstrates the potential of additive, high‐resolution direct‐writing techniques for the fabrication of organic electronics operating in the high‐frequency regime.

Side chain engineering of fluorinated benzothiadiazole‐based polymers: Improving the charge transport in organic field‐effect transistors

AbstractThree donor‐acceptor (D‐A) polymers P1–P3 are designed and synthesized, with 4,7‐dibromo‐5,6‐difluorobenzo[c][1,2,5]thiadiazole (FBT) as A and thiophene derivatives as D. All polymers show good thermal stability. The UV–vis absorption spectra show that P1 has too strong aggregation in solution, and it has no obvious temperature‐dependent aggregation (TDA) performance, which is also revealed in the variable temperature UV–vis absorption spectra. P2 film shows the same aggregation as in solution, P3 film shows stronger aggregation than that in solution. Polymers P1 and P2 both have strong TDA properties. Organic field effect transistors (OFETs) are prepared based on polymers P1, P2, and P3. OFETs devices prepared with high molecular weight polymers have better performance, and the polymer with 2‐nonyltridecyl side chain leads to the highest hole mobility around 0.252 cm2 V−1 s−1. The results show that the application of high molecular weight polymers and the selection of appropriate side chains are very important for the charge transport performance of OFETs.

Corona Poling Induced Phase Transition to Highly Polar Phase in P(VDF-TrFE-CFE) Dielectric and Charge Transport of Organic Field-Effect Transistors.

Increasing the number of charge carriers flowing through the charge transport channel to improve the electrical performance of organic field-effect transistors (OFETs) is important because it leads to a low driving voltage and a high drain current value. This paper proposes a new strategy, the corona poling process, to enhance the electrical performance of OFETs using an external electric field when forming a dielectric film using a PVDF-based high-k dielectric terpolymer, P(VDF-TrFE-CFE). A corona poling process was applied to align the dipoles with high-k dielectric molecules and improve the capacitance, thereby increasing the number of charge carriers. Through this process, by observing the phase transition of a PVDF dielectric through a corona poling process in the GIWAXS data, the phase transition through an external electric field was thoroughly revealed for the first time. As a result, the capacitance of high-k dielectric films can be improved, and the amount of charge carriers can be increased by a simple corona poling process. In addition, to reduce the effect of deep trap sites caused by the dipole alignment, a thin low-k dielectric, polystyrene (PS), was introduced between the active and high-k dielectric layers to provide trap site passivation, thereby increasing the electrical performance of the OFET. Therefore, through this strategy, using a diketopyrrolopyrrole (DPP)-based donor-acceptor (D-A) copolymer as an active material of OFET, the average saturation region hole mobility was improved from 0.34 to 0.60 cm2/Vs. Thus, the electrical performances of the OFETs were improved by enhancing the capacitance through the corona poling process and reducing the charge carrier trap sites introduced by the high-k and low-k bi-layer dielectric layer. Importantly, this work offers a new strategy for the post-treatment to improve electrical performance of organic devices.

Enhancement of Stability in n-Channel OFETs by Modulating Polymeric Dielectric.

In this study, a high-K material, aluminum oxide (AlOx), as the dielectric of organic field-effect transistors (OFETs) was used to reduce the threshold and operating voltages, while focusing on achieving high-electrical-stability OFETs and retention in OFET-based memory devices. To achieve this, we modified the gate dielectric of OFETs using polyimide (PI) with different solid contents to tune the properties and reduce the trap state density of the gate dielectric, leading to controllable stability in the N, N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13)-based OFETs. Thus, gate field-induced stress can be compensated for by the carriers accumulated due to the dipole field created by electric dipoles within the PI layer, thereby improving the OFET's performance and stability. Moreover, if the OFET is modified by PI with different solid contents, it can operate more stably under fixed gate bias stress over time than the device with AlOx as the dielectric layer only can. Furthermore, the OFET-based memory devices with PI film showed good memory retention and durability. In summary, we successfully fabricated a low-voltage operating and stable OFET and an organic memory device in which the memory window has potential for industrial production.

Organic Semiconductor Single Crystal Arrays: Preparation and Applications

The study of organic semiconductor single crystal (OSSC) arrays has recently attracted considerable interest given their potential applications in flexible displays, smart wearable devices, biochemical sensors, etc. Patterning of OSSCs is the prerequisite for the realization of organic integrated circuits. Patterned OSSCs can not only decrease the crosstalk between adjacent organic field-effect transistors (OFETs), but also can be conveniently integrated with other device elements which facilitate circuits application. Tremendous efforts have been devoted in the controllable preparation of OSSC arrays, and great progress has been achieved. In this review, the general strategies for patterning OSSCs are summarized, along with the discussion of the advantages and limitations of different patterning methods. Given the identical thickness of monolayer molecular crystals (MMCs) which is beneficial to achieve super uniformity of OSSC arrays and devices, patterning of MMCs is also emphasized. Then, OFET performance is summarized with comparison of the mobility and coefficient of variation based on the OSSC arrays prepared by different methods. Furthermore, advances of OSSC array-based circuits and flexible devices of different functions are highlighted. Finally, the challenges that need to be tackled in the future are presented.