Two-coordinate, coinage metal carbene-metal-amide (cMa) emitters have garnered attention due to their near unity photoluminescence quantum yields, color tunability, and short radiative lifetimes. However, due to their intrinsically high energy HOMO and LUMO levels, there has been difficulty incorporating them into charge balanced organic light-emitting diodes (OLEDs). Here, four new cMa complexes were prepared where the HOMO was stabilized by using cyano or trifluoromethyl electron withdrawing groups on the donor moiety and the LUMO was stabilized using a carbene acceptor with a low reduction potential. These modifications resulted in cMa complexes with sky-blue emission, high quantum yields (ΦPL > 0.95), and short radiative lifetimes (τ = 225 ns). The resultant vacuum-deposited OLED devices based on Au Bim ( C F 3 ) 2 PAC ${\mathrm{Au}}_{{\mathrm{Bim}}{{{( {{\mathrm{C}}{{{\mathrm{F}}}_3}} )}}_2}}^{{\mathrm{PAC}}}$ with SiCzCz/SiTrzCz2 cohost system display blue electroluminescence at 470 nm and external quantum efficiency of 8%.

We demonstrate the scaling of air-bridge Si thermophotovoltaic (TPV) technology to a 38 cm2 mini-module consisting of 40 individual cells (0.68 cm2 each) arranged in a 10 × 4 series-parallel connected array. The individual cells achieve an open-circuit voltage (VOC) of 643 ± 2 mV, a short-circuit current (ISC) of 270 ± 6 mA (current density of 399 ± 8 mA/cm2), a fill factor (FF) of 0.57 ± 0.01, a maximum power output (Pmax) of 99 ± 2 mW (output power density of 146 ± 3 mW/cm2), and a power conversion efficiency (PCE) of 18.0% ± 0.3% at 1,990 K. For the 5.2 × 7.3 cm module, VOC = 4.5 ± 0.5 V, ISC = 0.45 ± 0.15 A, FF = 0.45 ± 0.09, Pmax = 930 ± 40 mW, and PCE = 11% ± 3% are recorded at 2,230 K. We discuss current limitations to Si TPV module efficiency and possible routes for improvement.

Charge injection, transport and recombination in thin-film organic electronic devices is predicted to be filamentary on the nanoscale owing to energetic disorder. However, direct experimental evidence of this phenomenon has remained elusive. Here we study small molecule organic light-emitting diodes using super-resolution microscopy and find that their electroluminescence is spatially non-uniform at submicrometre length scales. The local electroluminescence intensity varies by up to 30% relative to the mean and flickers stochastically on millisecond-to-second timescales. These inhomogeneities are neither observed in photoluminescence nor polycrystalline organic light-emitting diodes, and differ for the highest- and lowest-energy components of the electroluminescence spectrum. They are consistent with intrinsic nanoscale variation in the local recombination rate induced by static disorder in amorphous thin films and should be present in a range of organic light-emitting diodes and other organic optoelectronic devices. Our observations should lead to improved models of nanoscale charge transport that benefit the design and performance of organic optoelectronic devices.

Electrolyte-gated organic field-effect transistors (EGOFETs) are ideal for biosensing, as they operate at low voltages and directly transduce changes in aqueous biological media. In this work, we characterize dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) and C10-DNTT EGOFETs in a phosphate-buffered saline (PBS) solution, demonstrating an intrinsic mobility of at least 2.8 ± 0.4 × 10-2 cm2/(V s), and a contact resistance of 3.1 ± 0.1 kΩ-cm. Transistors are scaled to channel lengths as small as 2 μm, and scaling effects, such as mobility degradation, threshold voltage roll-off, and drain-induced barrier lowering (DIBL) are characterized. While contact resistance and DIBL both affect the performance of scaled EGOFETs, the concomitant increase in transconductance and transit frequency ensures that scaling is a path to high performance. Proteins and induced pluripotent stem-cell cardiomyocytes are applied to 2 μm C10-DNTT transistors that maintain their performance after 1 week of incubation. C10-DNTT EGOFETs therefore may be scalable, high-performance, and stable candidates for biosensing applications.

Thermophotovoltaic (TPV) systems are a promising technology for power generation from thermal sources. Understanding how the efficiency of emerging TPVs is reported and how it relates to expected performance under realistic operating conditions is important for deployment of this technology and can inform future progress in the field. This work provides an overview of the main efficiency characterization techniques used today, including full and partial TPV irradiance, and direct and indirect (optical) heat transfer measurements. The overall steps of each method are discussed, along with their respective advantages and shortcomings from the perspective of mimicking practical operation. By surveying current methodologies, this study highlights areas for improvement and seeks to guide in selecting and refining efficiency characterization methods for TPV systems.

Floquet engineering, where an oscillating electric field modifies quantum states, is a promising tool to manipulate quantum systems coherently. For example, the valley-selective A.C. Stark effect can break time-reversal symmetry in monolayer transition metal dichalcogenides by lifting valley degeneracy. However, Floquet engineering has often been limited by the requirement of an ultrashort optical pulse with a high enough pulse energy. Here, based on a cavity structure with monolayer WSe2, we demonstrate that cavity effects can enhance effective Floquet dressing power by orders of magnitude. The strong enhancement also enables us to build an efficient chirality all-optical switch by the Floquet effect. Our study opens up the possibility to exploit Floquet engineering and other nonlinear phenomena for efficient optical devices of low-dimension materials.

This chapter is focused on describing the essential methods used in fabricating OLEDs, organic solar cells, transistors, and other associated devices. The first section discusses materials purity and how to achieve it to ensure that the device performance is repeatable and is not affected by impurity reactions. Next, techniques for film deposition, and the control of morphology and interfaces are described. The next step in device fabrication is introducing patterning methods with precision ranging from micrometers to meters. Finally, a brief description of large-scale manufacturing methods is provided.

Exciton transport and charge transfer in donor-acceptor (D-A) heterojunctions are critical in governing the power conversion efficiency in organic photovoltaics (OPVs). Despite advances in organic photovoltaic materials, exciton transport is hindered by structural disorder that limits device efficiency. Exciton polaritons, formed through the strong coupling of cavity-coupled organic materials, exhibit delocalized states that enhance exciton transport and reduce the effects of disorder. Using transient absorption spectroscopy, we explore strong coupling in D-A heterojunctions integrated with a distributed Bragg reflector "open cavity." The delocalized hybrid polariton state slows charge transfer compared to non-cavity-coupled control samples. These findings underscore the role that polaritons play in exciton transport and charge transfer. Understanding and controlling this interaction, along with the optimization of photonic structures, may lead to increased performance of OPVs and polaritonic devices.

The chapter begins by clarifying what is meant by energy gap, energy bands, and energy bandwidth in the specific context of van der Waals bonded solids compared to chemically bonded conventional semiconductors. Conduction in organics occurs by either Ohmic or space charge limited transport. Disorder, which is a natural property of soft materials, limits both processes. One means to determine the conductivity mechanism is an analysis of the current–voltage characteristics of the film, which are the “Rosetta Stone” for interpreting the conduction process. The chapter ends with consideration of junctions—specifically metal–semiconductor junctions, and junctions between two dissimilar organic materials, known as heterojunctions. One interesting feature is that almost all junction devices, whether based on organic or inorganic semiconductors, have similar current–voltage characteristics. There is a simple reason why this is the case, which is discussed at the end of the chapter.

In this chapter, we consider the only exclusively electronic device pursued in organic electronics: the organic thin film transistor (OTFT). The discussion begins by describing the basic architectures and functionality of OTFTs, followed by considering their operating principles based on the gradual channel approximation that simulates the transfer characteristics of most OTFTs with reasonable accuracy. Essential operating characteristics beyond their transfer functions, including dynamic range, frequency response, and noise, conclude the discussion. Several common OTFT architectures such as back-gated, ambipolar, and complementary logic devices are introduced This is followed by a section on materials and morphologies used in p- and n-channel transistors with gate geometries as small as 1 μm. After a discussion of the stability of OTFTs, the chapter ends with a description of several potential applications such as in wearable electronics and medical devices whose ultrathin form factors are nearly imperceptible to the user. Furthermore, they can fulfill needs in the diverse and large sensor markets.

Long-range coherence of the part-matter, part-light exciton-polariton has potential applications in all-optical logic that combine the large nonlinearity of the matter component with the delocalization by the light component. A polariton condensate has been shown to have long-range coherence, although the formation of a condensate requires complex device fabrication and well-defined operation conditions. In this work, we demonstrate a Mach-Zehnder interferometer that exhibits room-temperature, long-range coherent propagation of Bloch surface wave polaritons (BSWPs) that does not depend on the formation of a condensate. Due to strong coupling of the organic exciton and the delocalized BSW supported by a distributed Bragg reflector (DBR), the hybrid light-matter states sustain coherence over distances of similar to 50 mu m, giving rise to wavelength-dependent interference patterns within the devices. Our results show that the BSWP represents a promising platform for room-temperature coherent polaritonic devices, thus enabling integrated photonic circuits that operate under ambient conditions.

We investigate the resilience of organic photovoltaic (OPV) cells to proton irradiation at doses equivalent to that experienced by spacecraft in low earth orbit. The OPVs, with their inherent flexibility, light weight, low temperature processing, and potential to achieve high specific power of 40 W/g, are promising candidates for energy production in space. However, their ability to withstand irradiation by high-energy incident radiation and subatomic particles characteristic of harsh space environments is yet unproven. We find that small-molecule OPVs grown by vacuum thermal evaporation are resistant to degradation by 30 keV proton irradiation, in contrast to polymer-based OPVs that suffer a 50% efficiency loss under similar conditions. Thermal annealing at low temperatures significantly restores the polymer-based OPV power conversion efficiency. The loss of efficiency is attributed to cleavage of pendant alkyl groups on the polymers, resulting in cross-linking and the subsequent formation of deep electronic traps.

This chapter focuses on the materials, structures, and applications of organic photovoltaic cells (OPVs). Since OPVs are a specialized type of photodiode optimized for converting solar into electrical energy, this chapter builds heavily on Chapter 7. We first calculate the thermodynamic limits to OPV power conversion efficiency for single junction and multijunction cells. Attention is paid to the unique aspects and applications of OPVs taking advantage of optical transparency in the visible, flexibility, and high reliability. Next, the optimal morphologies for bulk heterojunction active regions and the materials used in high efficiency cells are examined. The operational lifetime of a solar cell is of considerable importance. Thus, a comprehensive discussion is devoted to OPV reliability, and the various failure mechanisms that they undergo as they age. Finally, a discussion of the practical aspects to OPV implementation considers arrays of OPVs and the efficiency penalties incurred in modules.

This chapter describes a few of the most important unanswered questions concerning organic materials science and some of the major problems that still need solution for organic devices to meet their anticipated high performance. Some of the challenges that confront the field require the filling of gaps in our understanding of the physics and chemistry of disordered materials, and others are significant engineering challenges that require greater focus to achieve better solutions than are currently available. Beyond describing these fundamental challenges, the chapter also introduces a few device types that have not yet been realized but offer opportunities into which the field can grow over the next several decades. In short, this chapter is meant to inspire students and practitioners in organic electronics to seize on these challenges to exploit the nearly limitless opportunities waiting to be exploited.

The performance of organic photovoltaic (OPV) devices has improved steadily since their introduction in the 1980's. The introduction of the bulk heterojunction and fullerene based acceptors in the early 2000’s led to a large bump in efficiency that led to photoconversion efficiencies > 10%. The next big step was int eh introduction of nonfullerene acceptors (NFAs), which replaced fullerenes with acceptor-donor-acceptor (ada) acceptors. The ada accepts shifted the absorption bands deep into the red end of the spectrum and gave OPVs with high short circuit currents. These ada materials are organic materials comprised of a range of donor and acceptor groups with an emphasis on thiophene based materials. We are investigating a different approach to ada (and dad) materials, incorporating porphyrin and dipyrrin donors as well as dipyrrin acceptors in the ada and dad structures. This has allowed us to prepare materials with absorption band edges deep into the nearinfrared, with HOMO/LUMO energies close to those of conventional ada materials. In my talk I will discuss our design strategies and most recent results with NFA comprised of porphyrin and dipyrrin building blocks as well as our most recent OPV results with these materials.

This textbook provides the essential principles of organic electronics from its fundamental concepts through to describing archetype devices that exploit the unique properties of the immense materials family of organic semiconductors in use today. The book should give undergraduates, graduate students (at both the Masters and PhD levels), and practicing engineers a solid introduction and background to the field. While it is assumed that the reader has some familiarity with conventional semiconductors and devices, deep expertise is not needed as essential background material is provided in the text. Furthermore, a background in chemistry is not required. The first four chapters introduce the basic physics of organic semiconductors, starting with materials structure, then introducing the fundamentals of their optical and electronic properties. The ensuing chapters cover specific devices and how to make them, the challenges that yet remain to achieve even higher performance, and their potential applications. The device chapters cover organic light emitting diodes (OLEDs), photodetectors and solar cells, and thin film transistors. The book closes with a chapter on the challenges and opportunities that still confront this rapidly growing field.

An organic molecule is one that is carbon rich, or carbon based. Many of these molecules, when in the solid phase, are electronic materials. Organic materials are also “soft” materials: they are the substances of which plastics are composed, and their relatively weak intermolecular bonding forces make them exceptionally lightweight, malleable, bendable, and mouldable into a variety of shapes. Hence, while conventional semiconductor circuits are inherently two-dimensional, organics can take on any number of forms such as in foldable displays, “electronic fabrics,” and active sensors that conform to the skin. This chapter introduces many of the remarkable characteristics of organic semiconductors by highlighting their most useful applications in displays, lighting, solar cells, and sensors. The chapter then describes some of the important advances made over the years by providing a brief look at the history of organic electronics, starting with the “discovery” of organic semiconductors, and culminating with the current period of widespread adoption of organic semiconductor devices.

This chapter begins by informing the reader how to “decode” chemical formulas and introduces some of useful chemistry terminology. This discussion is targeted at those with little or no background in organic chemistry. Next, the terminology of crystal structure provides a second vocabulary that is useful in communicating concepts relating to the morphology of thin films that comprise organic devices. This leads to a discussion of how the organics are bonded in solids. There are four types of bonds to consider: covalent, ionic, electrostatic (into which the important class of dipolar van der Waals bonds fall), and hydrogen bonds. Following this chapter, the reader should be prepared for subsequent discussions on the optical and electronic properties of materials comprising modern, thin film organic electronic devices.

Organic light-emitting diodes (OLEDs) have wrought a revolution in the ways that humans and machines communicate and interact. This chapter focuses on their principles of operation, and the application space filled by OLEDs in displays and lighting. A key to understanding OLEDs is their connection to elements of vision and how color is perceived. Precise quantification of their performance then lays the foundation for comparison of results between laboratories as well as in helping to determine how individual devices will perform as components of lighting and display systems. The first part of the chapter describes these factors, then moves on to discuss the design of modern OLEDs, and how displays and lighting fixtures are made. The chapter concludes with a discussion of the means and standards used to quantify device reliability, and to project how long laboratory devices will last when used in realistic, everyday environments.