Photocrosslinker‐Based Direct Microlithography for Organic Electronic Devices: From Patterning Capability to Multifunctionality

P-Type Chemical Doping-Induced High Bipolar Electrical Conductivities in a Thermoelectric Donor–Acceptor Copolymer

Increasing demand for portable and flexible electronic devices requires seamless integration of the energy storage system with other electronic components. This ever-growing area has urged on the rapid development of new electroactive materials that not only possess excellent electrochemical properties but hold capabilities to be fabricated to desired shapes. Ideally, these new materials should have minimal impact on the environment at the end of their life. Nitroxide radical polymers (NRPs) with their remarkable electrochemical and physical properties stand out from diverse organic redox systems and have attracted tremendous attention for their identified applications in plastic energy storage and organic devices. In this review, we present a comprehensive summary of NRPs with respect to the fundamental electrochemical properties, design principles and fabrication methods for different types of energy storage systems and organic electronic devices. While highlighting some exciting progress on charge transfer theory and emerging applications, we end up with a discussion on the challenges and opportunities regarding the future directions of this field.

Development in the field of organic electronics has hinged upon structural and fundamental advancements in the field of conjugated polymers owing to their potential advantages over inorganic and small molecule organic semiconductors. Conjugated polymers allow for the manufacture of low-cost, light-weight, flexible, organic electronic devices with outstanding applications in organic photovoltaics, organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), polymer solar cells (PSCs), and polymer light emitting diodes. Chemists can design and synthesize a large number of conjugated polymers with different architectures and functional moieties to fulfill the requirements of such organic devices. This chapter focuses on different conjugated polymer systems with 1D and 2D topological structures and summarizes the performances of the different types of conjugated polymers in devices such as OLEDs, OFETs, and PSCs. Finally, future research opportunities in this exciting research field are discussed.

The implementation of flexible Organic Electronic (OE) devices in a large variety of consumer applications (generation of electricity, visualization of information, lighting, sensing, etc.) will significantly improve our everyday life. The typical OE device (e.g. a organic photovoltaic cell—OPV) consists of multilayered structures (30–200 nm thick each) fabricated onto rigid (e.g. glass) and/or flexible substrates (as PET, PEN) from transparent and electrically active organic nanolayers. The OE device core is the active or the organic semiconducting (polymer or small molecules) layer, that absorbs photons and generates electric charges, sandwiched between the device electrodes. Finally, the device is encapsulated by barrier layers for the protection of the photoactive layers against degradation and corrosion due to atmospheric gas penetration inside the device. The understanding of the correlation between the polymer blend structure and its optical and electrical properties, and the achievement of the desirable morphology at nanometer scale, is a prerequisite in order to optimize the device performance and stability. Spectroscopic Ellipsometry (SE) from the infrared to the visible and far ultraviolet spectral region has been widely used to provide significant insights on the optical properties, blend morphology, and composition of the polymer blends that are used as active layers in OE devices. In this chapter, we summarize on the latest advances in the implementation of SE from the infrared to the visible and ultraviolet spectral region, for the investigation of the optical and electronic properties, composition profile and structure of polymer nanomaterials that are used as organic semiconductors and transparent electrodes for OE devices, and we discuss the effect of their nanoscale structure on their properties and functionality.

Designing π-conjugated polymers for organic electronics

Understanding the morphology and electronic properties of poly(fullerene)s is crucial for the development of new organic devices. This work addresses the fabrication and characterization of Langmuir–Schaefer (LS) films of poly(fullerene)s based on C60 with short (HSS8) and long (HSS16) sidechains, solubilized in chloroform or xylene. In addition, density functional theory (DFT) calculations are used to optimize the molecular geometries, determine energies, and investigate the influence of solvent applied. Depending on the organic solvent, floating material isotherms indicate the formation of disordered aggregates in the aqueous subphase. The influence of solvent in LS films is also evidenced by way of atomic force microscopy (AFM), UV‐vis, and cyclic voltammetry (CV) measurements. From DFT calculations, the arms of the poly(fullerene)s start to extend from an initial position of surrounding the fullerene sphere. In AFM measurements, depending on the organic solvent, the roughness significantly reduces, while the homogeneity is much higher. In UV‐vis and CV measurements, the propensity to form aggregates depends mainly on the polarization of the solvent and is directly related to the maximum absorption, oxidation, and reduction peaks. From the optical bandgap energy values, the poly(fullerene)s studied here present high potential for application in organic electronic devices.

Organic electronic devices (OEDs) are quite suitable for use in flexible devices due to their ruggedness and flexibility. A number of researchers have studied the use of OEDs on flexible substrates in transparent, flexible devices in the near future. However, water and oxygen can permeate through the flexible substrates and can reduce the longevity of OEDs made from organic materials, which are weak to moisture and oxygen. In order to prevent the degradation of the OEDs, researchers have applied an encapsulation layer to the flexible substrates. In this study, Al2O3/plasma polymer film/Al2O3 multi-layers were deposited on polyethylene-naphthalate substrates through a combination of atomic layer deposition and plasma-enhanced chemical vapor deposition (PECVD). The plasma polymer film, which is located between the Al2O3 films, is deposited via PECVD with the use of a tetrakis(trimethylsilyloxy)silane precursor. The power of the plasma deposition varied from 10 to 50 W. The hydrophobicity of the plasma polymer film surfaces was investigated by measuring the water contact angle. The chemical structures of the plasma polymer films were measured via ex-situ Fourier transform infrared analysis. The permeation curves of the various films were analyzed by performing a calcium (Ca)-test.

This review highlights selected examples, published in the last three to four years, of recent advance in the design, synthesis, properties, and device performance of quinoidal π-conjugated materials. A particular emphasis is placed on emerging materials, such as indophenine dyes that have the potential to enable high-performance devices. We specifically discuss the recent advances and design guidelines of π-conjugated quinoidal molecules from a chemical standpoint. To the best of the authors’ knowledge, this review is the first compilation of literature on indophenine-based semiconducting materials covering their scope, limitations, and applications. In the first section, we briefly introduce some of the organic electronic devices that are the basic building blocks for certain applications involving organic semiconductors (OSCs). We introduce the definition of key performance parameters of three organic devices: organic field effect transistors (OFET), organic photovoltaics (OPV), and organic thermoelectric generators (TE). In section two, we review recent progress towards the synthesis of quinoidal semiconducting materials. Our focus will be on indophenine family that has never been reviewed. We discuss the relationship between structural properties and energy levels in this family of molecules. The last section reports the effect of structural modifications on the performance of devices: OFET, OPV and TE. In this review, we provide a general insight into the association between the molecular structure and electronic properties in quinoidal materials, encompassing both small molecules and polymers. We also believe that this review offers benefits to the organic electronics and photovoltaic communities, by shedding light on current trends in the synthesis and progression of promising novel building blocks. This can provide guidance for synthesizing new generations of quinoidal or diradical materials with tunable optoelectronic properties and more outstanding charge carrier mobility.

Nanospheres lithography (NSL) is an economical technique, which makes use of highly monodispersed nanospheres such as deposition or etch masks for generating patterns with nanoscale features. Embedding nanostructures into organic electronic devices can endow them with unique capabilities and enhanced performance, which have greatly advanced the development of organic electronics. In this review, a brief summary of the methods for the preparation of monodispersed nanospheres is presented. Afterward, the authors highlight the recent advances of a wide variety of applications of nanospheres lithography in organic electronic devices. Finally, the challenges in this field are pointed out, and the future development of this field is discussed.

Organic electronic devices have demonstrated tremendous versatility in a wide range of applications including consumer electronics, photovoltaics, and biotechnology. The traditional interface of organic electronics with biology, biotechnology, and medicine occurs in the general field of sensing biological phenomena. For example, the fabrication of hybrid electronic structures using both organic semiconductors and bioactive molecules has led to enhancements in sensitivity and specificity within biosensing platforms, which in turn has a potentially wide range of clinical applications. However, the interface of biomolecules and organic semiconductors has also recently explored the potential use of natural and synthetic biomaterials as structural components of electronic devices. The fabrication of electronically active systems using biomaterials-based components has the potential to realize a large set of unique devices including environmentally biodegradable systems and bioresorbable temporary medical devices. This article reviews recent advances in the implementation of biomaterials as structural components in organic electronic devices with a focus on potential applications in biotechnology and medicine.

Organic electronic devices will play an important role in future technical applications because of their easy production and low costs. Besides intrinsic material properties, the performance of organic solar cells, light emitting diods and thin-film transistors depends strongly on the morphology, the occurring hetero-junctions, as well as on achieving an appropriate alignment of transport levels. To optimize the efficiency of organic devices it is, therefore, important to understand what limits their performance. The paper supports this concern by providing a general model for simulating the exciton and charge carrier transport in such building blocks. Due to the complex internal structure and the large aspect ratios of the active device regions, the procedure is based on drift-diffusion equa- tions. All of the necessary source, generation and recombination terms are included in the developed model. The applied numerics is based on finite difference approaches and especially on the Scharfetter-Gummel algorithm. Three examples, which prove the appli- cability of the established formalism to enhance the performance of organic devices are given. The performed simulations reveal interesting particularities of the carrier transport in these devices.

Kinetic Monte Carlo (KMC) simulations have emerged as an important tool to help improve the efficiency of organic electronic devices by providing a better understanding of their device physics. In the KMC simulation of an organic device, the reliability of the results depends critically on the accuracy of the chosen charge-transfer rates, which are themselves strongly influenced by the site-energy differences. These site-energy differences include components coming from the electrostatic forces present in the system, which are often evaluated through electric potentials described by the Poisson equation. Here we show that the charge-carrier self-interaction errors that appear when evaluating the site-energy differences can lead to unreliable simulation results. To eliminate these errors, we propose two approaches that are also found to reduce the impact of finite-size effects. As a consequence, reliable results can be obtained at reduced computational costs. The proposed methodologies can be extended to other device simulation techniques as well.

Materials Interface Engineering In their Review Article (10.1002/adfm.202515507), Shern-Long Lee and co-workers critically examine the impact of interfacial molecular orientation on organic electronic devices. By modulating the alignment of organic semiconductors at interfaces, fundamental properties such as electrode work function and charge transport pathways can be rationally engineered, thereby optimizing device efficiency and stability. The review provides a holistic perspective, demonstrating that the synergy between experimental synthesis, characterization, and simulation is essential for designing the next generation of high-performance organic electronics.

Promising applications of organic materials in next-generation electronic and optoelectronic devices have driven extensive efforts to form various composites. Electronic and optoelectronic devices fabricated utilizing organic materials, such as organic thin film transistors, organic light-emitting diodes, and organic solar cells, have been extensively studied. However, relatively little work has been done on organic memory devices fabricated utilizing hybrid composites. Among the various kinds of composites, hybrid composites based on fullerene C60 and poly(N-vinylcarbazole) (PVK) organic materials have become particularly attractive because of their potential applications in organic electronic devices. Even though some works concerning the organic memory devices consisting of organic/metal/organic structures formed by using evaporation methods, very few studies concerning the memory effect of the organic/inorganic hybrid structures fabricated by using spin-coating techniques have been reported. This paper reports data for the memory effects of the effect of C60 existence on the flat-band voltage shift of nonvolatile polymer memory devices with the PVK and the C60 nanocomposites active layers was described.

This article reviews the recent advances in organic electronics based on polymer blends with one-dimensional (1D) nanowires (NWs) of π-conjugated polymers. Self-assembled polymer semiconducting NWs are fascinating building blocks for their directional extension of inter- and intramolecular π-conjugation. This extensive conjugation provides unique electrical and optical properties that benefit applications in organic electronic devices. Outstanding performances are particularly expected from blending these NWs with insulating polymers or semiconducting molecules. Several representative reports describing NWs prepared from semiconducting/insulating polymer blends, conjugated block copolymers, or electrospinning for use as high-performance organic thin-film transistors (OTFTs) are discussed. The concepts of phase-separation behavior and the growth of crystalline NWs from multi-phase blend solutions are also illustrated. Research into the solubility-induced formation of NWs from semiconducting polymer/n-type small molecule blends for high-efficiency organic photovoltaic solar cells (OPVs) is introduced. In addition, the effects of the chemical properties of conjugated polymers on the optical and electrical properties of NWs and the use of ordered NW structures in OPVs are summarized. This critical review provides insights and a new perspective on the optimization of blend morphologies, which consequently enhances the performance of organic electronic devices.