Biomaterials‐based organic electronic devices

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.

Organic electronics has made great progress in the past decades, which is inseparable from the innovative development of organic electronic devices and the diversity of organic semiconductor materials. It is worth mentioning that both of these great advances are inextricably linked to the development of organic high-performance semiconductor materials, especially the representative n-type organic small-molecule semiconductor materials with high electron mobilities. The n-type organic small molecules have the advantages of simple synthesis process, strong intermolecular stacking, tunable molecular structure, and easy to functionalize structures. Furthermore, the n-type semiconductor is a remarkable and important component for constructing complementary logic circuits and p-n heterojunction structures. Therefore, n-type organic semiconductors play an extremely important role in the field of organic electronic materials and are the basis for the industrialization of organic electronic functional devices. This review focuses on the modification strategies of organic small molecules with high electron mobility at molecular level, and discusses in detail the applications of n-type small-molecule semiconductor materials with high mobility in organic field-effect transistors, organic light-emitting transistors, organic photodetectors, and gas sensors.

Conventionally, P–N junctions have played an important role as a key unit in most semiconductor electronic devices. P–N junctions based on organic semiconductors have also been researched widely, but it is difficult to develop solution‐processing‐based organic semiconductor P–N junctions because of their similar solubility in common organic solvents. For this reason, most organic planar heterojunctions have been based on deposition by thermal evaporation or transfer film via additional complicated processing. In this study, using p‐type and n‐type conjugated polymers with selection of their orthogonal solvents, a conjugated polymer bilayer P–N heterojunction structure is developed via simple solution processing. The developed structure is then used in novel organic electronic applications, such as organic rectifier diodes, organic field‐effect transistors with highly balanced ambipolar charge transport properties, integrated circuits, and even organic phototransistors that display a photoresponse from the visible to the near‐infrared (NIR) range with the generation of a photocurrent at the P–N heterointerface in the channel region. The polymeric P–N junction structure can be applied in various organic electronic devices via a simple printing process, which can contribute to the development of new functionalized organic electronics systems.

Background: Organic field effect transistors (OFETs), used in the fabrication of nanosensors, are one of the most promising devices in organic electronics because of their lightweight, flexibility, and low fabrication cost. However, the optimization of such OFETs is still in an early stage due to the minimal analytical and numerical models presented in the literature. Objective: This research presses to demonstrate a numerical carrier transport model based on the finite element method (FEM) to investigate the I-V characteristic of OFETs. Methods: Two various organic semiconductor materials have been included in the study, polyaniline and pentacene, where micro-scale, as well as nano-scale models have been presented. OFETs regarding channel length, dielectric thickness, and doping level impact have been studied. We nominated the threshold voltage, the on/off current ratio, the sub-threshold swing, and the field effect mobilities as the primary output evaluating parameters. Results: The numerical model has shown the criticality of the doping effect on tuning the device flowing drain current to exceed 300 μA saturation current, along with a threshold voltage of -0.1 V under a channel length of 30 nm. Conclusion: The study highlights the effectiveness of polyaniline over pentacene as nano-channel length OFET due to the boosted conductivity of polyaniline concerning pentacene.

Synthesis of n‐type organic semiconductors with high electron mobilities, good environmental stability, and good processability is an urgent task in current organic electronics. This is because most of π‐conjugated materials are p‐type and prefer to transport positive hole carriers. In this article, a series of new dicarboxylic imide‐substituted poly(p‐phenylene vinylenes) (DI‐PPVs) were first synthesized. They exhibited a high electron affinity of 3.60 eV and thus are able to transport electrons. The polymers showed tunable solubility in common organic solvents and high chemical and thermal stability. They remain rigidity of the PPV backbone, and strong interchain π‐stacking was observed in thin films by X‐ray diffraction measurement. All these suggested that these polymers could serve as good candidates as n‐type semiconductors in organic electronic devices such as n‐channel field‐effect transistors and all polymer‐based solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 186–194, 2010

Much effort is being dedicated to develop small organic molecules for their use in organic electronic devices, for which a key parameter is the mobility of charge within the active organic layers. Important advances achieved in this field have been therefore connected to the enhancement of the charge carrier mobility of organic semiconductors. In this communication we present a new family of stable high-mobility organic p-type semiconductors based on the electronrich 10,15-dihydro- 5H -diindolo[3,2-a:3',2'-c]carbazole (triindole) platform. We show how it is possible to tune their electronic properties as well as their supramolecular organization through chemical functionalization.

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.

Organic molecular semiconductors have been paid great attention due to their advantages of low-temperature processability, low fabrication cost, good flexibility, and excellent electronic properties. As a typical example of five-ring-fused organic semiconductors, a single crystal of pentacene shows a high mobility of up to 40 cm2 V-1 s-1, indicating its potential application in organic electronics. However, the photo- and optical instabilities of pentacene make it unsuitable for commercial applications. But, molecular engineering, for both the five-ring-fused building block and side chains, has been performed to improve the stability of materials as well as maintain high mobility. Here, several groups (thiophenes, pyrroles, furans, etc.) are introduced to design and replace one or more benzene rings of pentacene and construct novel five-ring-fused organic semiconductors. In this review article, ∼500 five-ring-fused organic prototype molecules and their derivatives are summarized to provide a general understanding of this catalogue material for application in organic field-effect transistors. The results indicate that many five-ring-fused organic semiconductors can achieve high mobilities of more than 1 cm2 V-1 s-1, and a hole mobility of up to 18.9 cm2 V-1 s-1 can be obtained, while an electron mobility of 27.8 cm2 V-1 s-1 can be achieved in five-ring-fused organic semiconductors. The HOMO-LUMO levels, the synthesis process, the molecular packing, and the side-chain engineering of five-ring-fused organic semiconductors are analyzed. The current problems, conclusions, and perspectives are also provided.

Molecular doping is an effective tool to enhance bulk conductivity, increase carrier injection and de-activate electron or hole traps in organic molecular and polymer semiconductors. Considerable effort has been directed toward the synthesis of powerful and stable p-type and n-type molecular dopants over the past decade.[1,2] This talk reviews a range of molecular redox agents used in organic electronics, with focus on strong reductants and oxidants for organic semiconductors with low electron affinity (EA) and large ionization energy (IE), respectively. In particular, we look at air-stable dimers, e.g. [RuCp*Mes]2, formed of 19-electron organometallic sandwich compounds able to reduce organic semiconductors with EA well below 3 eV.[3] We review powerful single-electron molecular oxidants, e.g. F6-TCNNQ and CN6-CP, which can introduce holes in organic semiconductors with IE larger than 5.6 eV. Applications of these n- and p-dopants to improve the conductivity of carrier injection layers and create large gap semiconductor p-i-n structures are described.[4] The last part of the talk focuses on recent work on adduct-based p-doping of organic semiconductors, applicable to a range of hole transport materials.[5][1]S. Barlow, S.R. Marder, X. Lin, F. Zhang and A. Kahn, Electrical Doping of Organic Semiconductors with Molecular Oxidants and Reductants, Handbook of Conducting Polymers (2019)[2] G. Song, S.B. Kim,S. Mohapatra, Y. Qi, T. Sajoto, A. Kahn, S.R. Marder, S. Barlow, n-Doping of Organic Electronic Materials Using Air-Stable Organometallics, Adv. Mat. 24, 699 (2012)[3] X. Lin, B. Wegner, K. M. Lee, M. A. Fusella, F. Zhang, K. Moudgil, B. P. Rand, S. Barlow, S. R. Marder, N. Kochand A. Kahn, Beating the Thermodynamic Limit: Photo-Activation of n-Doping in Organic Semiconductors, Nature Materials 16, 1209 (2017)[4] H. L. Smith, J. T. Dull, S. Mohapatra, S. Barlow, S. Marder, B. P. Rand, and A. Kahn, Powerful organic molecular oxidant and reductant enable a large gap, blue light-emitting organic homojunction diode, ACS Appl. Mat. Int. 14, 2381 (2022)[5] N. Sakai, R. Warren, F. Zhang, S. Nayak, S. V. Kesava, Y.-H. Lin, H. S. Biswal, X. Lin, A. Kahn, M. Riede, P. K. Nayak and H. J. Snaith, Adduct-based p-doping of Organic Semiconductors, Nature Materials, 20, 1248 (2021)

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 semiconductors are poised to transform the world of circuit and display technology. Major electronics firms such as Philips and Pioneer, and smaller companies such as Cambridge Display Technology, Universal Display, and Uniax, are betting that the future holds tremendous opportunity for the low cost and sometimes surprisingly high performance offered by organic electronic and optoelectronic devices. Using organic light-emitting devices (OLEDs), organic full-color displays may eventually replace liquid-crystal displays (LCDs) for use with laptop and even desktop computers. Such displays can be deposited on flexible plastic foils, eliminating the fragile and heavy glass substrates used in LCDs, and can emit bright light without the pronounced directionality inherent in LCD viewing, all with efficiencies higher than can be obtained with incandescent light bulbs.

Organic spintronics can be divided into two major topics: magnetic field effect and spin injection. It has been shown that external magnetic field can significantly change photoluminescence, injection current, electroluminescence and photocurrent in organic semiconducting materials, which corresponds to magnetic field effect in organic semiconducting materials. In recent years, magnetic field effects in non-magnetic organic semiconducting materials have attracted intensive attention and research interest. They have emerged as powerful experimental tools to study useful and unuseful processes in charge-transport and excited states in organic electronic, optic and optoelectronic devices, providing effective approaches to tackle bottle-neck problems in charge-transport and excited states processes and offering scientific principles for muti-functional integration of magnetic, optical and electronic properties. In addition, magnetic field effects open new avenues to enhance energy conversion efficiency, frequency range and sensitivity in optoelectronic detecting or sensing devices. Furthermore, spin injection and its tuning on charge-transport and excited states processes based on ferromagnetic electrodes in organic semiconducting materials and devices can be used to develop novel functional spin-optoelectronic devices. This paper reviews the fundamental processes involved in the effects of magnetic field and spin injection on optoelectronic functions in organic semiconducting materials and devices.

The charge transport characteristics of organic semiconductors are one of the key attributes that impacts the performance of organic electronic and optoelectronic devices in which they are utilized. For improved performance in organic photovoltaic cells, light‐emitting diodes, and field‐effect transistors (FETs), efficient transport of the charge carriers within the organic semiconductor is especially critical. Characterization of charge transport in these organic semiconductors is important both from scientific and technological perspectives. In this review, we shall mainly discuss the techniques for measuring the charge carrier mobility and not the theoretical underpinnings of the mechanism of charge transport. Mobility measurements in organic semiconductors and particularly in conjugated polymers, using space‐charge‐limited current, time of flight, carrier extraction by linearly increasing voltage, double injection, FETs, and impedance spectroscopy are discussed. The relative merits, as well as limitations for each of these techniques are reviewed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

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.

In organic electronics, conductivity doping is used primarily to eliminate charge injection barriers in organic light‐emitting diodes, organic photovoltaics and other electronic devices. Therefore, research on conductivity doping is primarily focused on understanding and enhancing the properties of these doped layers. In contrast, this work shifts the focus from optimizing doped layers to leveraging the doping process as a tool for investigating fundamental material properties. Specifically, the dopant is used as an “agent” to enable the measurement of three critical parameters‐ ionization potential (IP), electron affinity (EA), and Coulomb interaction energy (VC) – that govern dopant ionization and play central roles in organic electronic devices in general. While these parameters can be measured experimentally, conventional approaches often involve intricate or indirect methods, such as spectral deconvolution, which may introduce ambiguities or fail to represent bulk properties. Here it is shown how consolidating the experimental data and simulations on the dopant ionization fraction and doped‐induced conductivity can be used to estimate the mean IP or EA of the embedded organic molecule, and VC of the embedded charge‐transfer complex. These results illustrate how measuring and simulating doped materials can provide access to the fundamental design parameters of organic electronic devices.