End-capped engineering of Quinoxaline core-based non-fullerene acceptor materials with improved power conversion efficiency

Improving the light-harvesting efficiency and boosting open circuit voltage are crucial challenges for enhancing the efficiency of organic solar cells. This work introduces seven new molecules (SA1-SA7) to upgrade the optoelectronic and photovoltaic properties of Q-C-F molecule-based solar cells. All recently designed molecules have the same alkyl-substituted Quinoxaline core and CPDT donor but vary in the end-capped acceptor subunits. All the investigated molecules have revealed superior properties than the model (R) by having absorbance ranging from 681 nm to 782 nm in the gaseous medium while 726 nm-861 nm in chloroform solvent, with the lowest band gap ranging from 1.91 to 2.19 eV SA1 molecule demonstrated the highest λmax (861 nm) in chloroform solvent and the lowest band gap (1.91 eV). SA2 molecule has manifested highest dipole moment (4.5089 D), lower exciton binding energy in gaseous (0.33 eV) and chloroform solvent (0.47 eV), and lower charge mobility of hole (0.0077693) and electron (0.0042470). At the same time, SA7 showed the highest open circuit voltage (1.56 eV) and fill factor (0.9166) due to solid electron-pulling acceptor moieties. From these supportive outcomes, it is inferred that our computationally investigated molecules may be promising candidates to be used in advanced versions of OSCs in the upcoming period.

The Blue Problem: OLED Stability and Degradation Mechanisms

OLED technology has revolutionized the display industry and is promising for lighting. Despite its maturity, there remain outstanding device and materials challenges to address. Particularly, achieving stable and highly efficient blue OLEDs is still proving to be difficult; the vast array of degradation mechanisms at play, coupled with the precise balance of device parameters needed for blue high-performance OLEDs, creates a unique set of challenges in the quest for a suitably stable yet high-performance device. Here, we discuss recent progress in the understanding of device degradation pathways and provide an overview of possible strategies to increase device lifetimes without a significant efficiency trade-off. Only careful consideration of all variables that go into OLED development, from the choice of materials to a deep understanding of which degradation mechanisms need to be suppressed for the particular structure, can lead to a meaningful positive change toward commercializable blue devices.

Room-temperature magnetoresistance in Ni78Fe22/C8-BTBT/Ni78Fe22 nanojunctions fabricated from magnetic thin-film edges using a novel technique

Molecular spintronic devices are gaining popularity because the organic semiconductors with long spin relaxation times are expected to have long spin diffusion lengths. A typical molecular spintronic device consists of organic molecules sandwiched between two magnetic layers, which exhibits magnetoresistance (MR) effect. Nanosized devices are also expected to have a high spin polarization, leading to a large MR effect owing to effective orbital hybridization. However, most studies on nanosized molecular spintronic devices have investigated the MR effect at low temperatures because of the difficulty in observing the MR effect at room temperature. Here we focus on high-mobility molecules expected to show long spin diffusion lengths, which lead to the observation of the MR effect in nanoscale junctions at room temperature. In this study, we fabricate magnetic nanojunctions consisting of high-mobility molecules, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), sandwiched between two Ni78Fe22 thin films with crossed edges. Transmission electron microscopy (TEM) images reveal that C8-BTBT molecular layers with smooth and clear interfaces can be deposited on the Ni78Fe22 thin-film edges. Consequently, we observe a clear positive MR effect, that is, R P < R AP, where R P and R AP are the resistances in the parallel (P) and antiparallel (AP) configurations, respectively, of two magnetic electrodes in the Ni78Fe22/C8-BTBT/Ni78Fe22 nanojunctions at room temperature. The obtained results indicate that the spin signal through the C8-BTBT molecules can be successfully observed. The study presented herein provides a novel nanofabrication technique and opens up new opportunities for research in high-mobility molecular nano-spintronics.

Experimental and theoretical study of europium-doped organometal halide perovskite nanoplatelets for UV photodetection with high responsivity and fast response

Herein, we investigate the role of Eu³⁺ doping on CH₃NH₃PbBr₃ nanoplatelets (NPLs) in terms of their optoelectronic properties and photodetection application through a combined experimental and theoretical approach. The introduction of EuCl₃ in the CH₃NH₃PbBr₃ crystal structure by a facile solvothermal method enabled the tuning of the lateral and vertical dimensions of the NSs to form large-area NPLs and finally monolayer nanocrystals. The appearance of low-angle diffraction peaks with Eu doping, which are observed in layered perovskite structures, confirms the formation of quasi-2D NPLs. The bandgap of the Eu-doped mixed halide perovskite systematically increases from 2.39 eV to 2.94 eV with increasing doping concentration. Interestingly, 10 mol% EuCl₃ doping in the pure CH₃NH₃PbBr₃ crystal dramatically enhances its absorbance and photosensitivity, resulting in high-performance photodetection. Under 405 nm excitation, the CH₃NH₃Pb_0.9Eu_0.1Br_2.7Cl_0.3 photodetector exhibits self-biased behavior with an on/off ratio >10³, which is very significant. The planar device achieves a responsivity as high as 5.29 A W^- and a detectivity of 1.06 × 10¹² Jones under 405 nm with a power density of 0.14 mW cm^-2 at 5 V. In addition, the device exhibits very fast response time with a rise/fall time of 17.5/38.5 μs, which is ∼4 times faster than the pristine CH₃NH₃PbBr₃ counterpart. A linear relationship of photocurrent with light intensity in the CH₃NH₃Pb_0.9Eu_0.1Br_2.7Cl_0.3 photodetector signifies low recombination or charge trapping loss. High-performance photodetection in the Eu-doped device is ascribed to the elimination of trap states and the fast charge transfer process. To obtain better insight into the doped system, DFT analysis of the electronic structure of EuCl₃-doped CH₃NH₃PbBr₃ was performed and the results are fully consistent with the experimental findings. It was revealed that EuCl₃ doping increases the density of states near the conduction band along with a blue shift in the bandgap as compared to that of the pristine perovskite, which in turn increases the built-in potential of the fabricated device, resulting in self-biased photodetection. This work paves the way for deeper understanding of lanthanide doping in perovskites and self-biased photodetection applications of a new family of Eu-doped mixed halide perovskite nanostructures.

Unrevealing the interaction between O2 molecules and poly(3-hexylthiophene-2,5-diyl) (P3HT)

Stability of π-conjugated organic materials remains a critical issue for applications in which these materials and devices based on them are exposed to ambient conditions. Particularly, the initial steps of the reversible and irreversible degradation by molecular oxygen exposure are still not fully explored. Here we present a theoretical study using density functional theory (DFT) to investigate the oxygen effects on the electronic properties of poly(3-hexylthiophene-2,5-diyl) (P3HT). Our results show that trap-states are introduced in the energy gap between the highest occupied and the lowest unoccupied molecular orbitals by the O₂ molecule and both singlet and triplet states can be formed irrespectively of the existence of chain defects. A crossing between the potential energy surfaces of singlet and triplet states was observed for smaller distances of the oxygen molecule to the nearest thiophene ring, which was identified as being the first step towards irreversible degradation.

Stability of π-conjugated organic materials remains a critical issue for applications in which these materials and devices based on them are exposed to ambient conditions.

Axially Chiral Bis-Cycloplatinated Binaphthalenes and Octahydro-Binaphthalenes for Efficient Circularly Polarized Phosphorescence in Solution-Processed Organic Light-Emitting Diodes

A new series of axially chiral binuclear Pt(II) complexes with bridging ligands of binaphthalenes and octahydro-binaphthalenes and auxiliary ligands of β-diketones were designed and prepared. These complexes, identified by spectral and electrochemical methods and single-crystal X-ray diffraction, emit an orange-red phosphorescence with a quantum yield up to 21% and 70% in solution and solid, respectively, due to the effect of steric hindrance from bridging ligands and the 2,3-position extension of chiral axis planes. They can be used as emitters in solution-processed organic light-emitting diodes to achieve luminance efficiency, asymmetry factor, and external quantum efficiency up to 5.4 cd A^-1, 3.0 × 10^-3, and 3.1%, respectively. Moreover, the essential relationships between their chemical structures and luminescence quantum efficiency and asymmetry factor are discussed, which affords explicit insights for designing circularly polarized luminescent materials and devices.

Approaches for Long Lifetime Organic Light Emitting Diodes

Organic light emitting diodes (OLEDs) have been well known for their potential usage in the lighting and display industry. The device efficiency and lifetime have improved considerably in the last three decades. However, for commercial applications, operational lifetime still lies as one of the looming challenges. In this review paper, an in-depth description of the various factors which affect OLED lifetime, and the related solutions is attempted to be consolidated. Notably, all the known intrinsic and extrinsic degradation phenomena and failure mechanisms, which include the presence of dark spot, high heat during device operation, substrate fracture, downgrading luminance, moisture attack, oxidation, corrosion, electron induced migrations, photochemical degradation, electrochemical degradation, electric breakdown, thermomechanical failures, thermal breakdown/degradation, and presence of impurities within the materials and evaporator chamber are reviewed. Light is also shed on the materials and device structures which are developed in order to obtain along with developed materials and device structures to obtain stable devices. It is believed that the theme of this report, summarizing the knowledge of mechanisms allied with OLED degradation, would be contributory in developing better-quality OLED materials and, accordingly, longer lifespan devices.

Degradation of OLED performance by exposure to UV irradiation

Organic light-emitting diode (OLED) displays are highly susceptible to the harsh environmental conditions found outdoors, like exposure to direct sunlight as well as UV radiation and storage temperature, resulting in a loss of luminance and lifespan, pixel shrinkage, and permanent damage and/or malfunction of the panel. Here, we fabricated top emission OLEDs (TEOLEDs) using Yb : LiF (1 : 1, 2 nm)/Ag : Mg (10 : 1, 16 nm) and Mg : LiF (1 : 1, 2 nm)/Ag : Mg (10 : 1, 16 nm) cathode units and the performances of the devices were investigated by subjecting them to UV radiation. A fabricated red TEOLED (control device), employing a standard Mg : LiF (1 : 1, 2 nm) electron injection layer (EIL) and an Ag : Mg (16 nm) cathode, showed a rapid decrease in luminance and a fast increase in driving voltage at 10 mA cm⁻² over time after UV irradiation for 300 h. However, a cathode unit comprising a Yb : LiF (1 : 1, 2 nm) EIL and an Ag : Mg (10 : 1, 16 nm) cathode showed no loss of luminance or increase in driving voltage at 10 mA cm⁻² over time after UV irradiation for 300 h. Therefore, we investigated the changes occurring in both cathode units due to UV irradiation using the lift-out FIB-TEM technique and EDS mapping. With UV irradiation for 300 h, Ag atoms migrated toward the center of the cathode, Mg atoms migrated toward the CPL, and no Mg atoms were observed in the EIL area. In contrast, we observed (i) no substantial migration of Ag atoms and they were located at the center of the cathode, (ii) no migration of Mg atoms toward the CPL layer, and (iii) no movement of Yb atoms after UV irradiation. Furthermore, the UV irradiated red TEOLED with an Mg : LiF (1 : 1, 2 nm) EIL showed (i) deterioration in electron injection into the emissive layer (EML) and an increase in the EIL/metal interface resistance, and (ii) a remarkable shift of the J–V curve to the higher voltage side, while almost no such changes were observed in the TEOLD with a Yb : LiF (1 : 1, 2 nm) EIL. Also, an almost identical RGB pixel emitting area was noticed in the Yb : LiF (1 : 1, 2 nm) based devices after UV irradiation for 300 h. These results suggest that Yb could become a good candidate for the cathode unit, providing better device stability against harsh environmental conditions as well as excellent electron injection properties.

This paper reports the influence of UV radiation on the interface of a co-deposited EIL and Ag : Mg (10 : 1) cathode unit and pixel shrinkage.

Interlayers Self-Generated by Additive-Metal Interactions in Organic Electronic Devices

The fundamental structure of all organic electronic devices is a stack of thin layers sandwiched between electrodes, with precise intralayer morphology and interlayer interactions. Solution processing multilayers with little to no intermixing is, however, technically challenging and often incompatible with continuous roll-to-roll, high-speed manufacturing. Here, an overview of a recently developed methodology for self-generation of interlayers positioned between the active layer and metal contact is presented. The interlayer material is blended as an additive in the active layer and migrates to the organic/metal interface during metal deposition. The driving force for this migration is additive-metal interactions. The generated interlayer positions an interfacial dipole that reduces barriers for charge transfer across the organic/metal interface. This methodology is generic and, as reported here, the self-generated interlayers significantly improve the performance of many devices. Importantly, this approach is compatible with printing and reel-to-reel processing. Directives toward additive selection, processing conditions and integration in future applications are also discussed.

Versatile Exciplex-Forming Co-Host for Improving Efficiency and Lifetime of Fluorescent and Phosphorescent Organic Light-Emitting Diodes

We report a new efficient exciplex-forming system consisting of a biscarbazole donor and a triazine-based acceptor. The new exciplex was characterized with a high photoluminescence quantum yield up to 68% and effective thermally activated delayed fluorescence behavior. The BCzPh:3P-T2T (2:1, 30 nm) blend was examined not only as an emitting layer (device D1) but also a reliable co-host of fluorescent and phosphorescent emitters for giving highly efficient exciplex-based organic light-emitting diodes (OLEDs) with a high maximum external quantum efficiency of 15.5 and 29.7% for devices doped with 1 wt % C545T (device D2) and 8 wt % Ir(ppy)₂(acac) (device D4), respectively. More strikingly, a strongly enhanced lifetime ( T₇₅ = 16 927 min.) of the C545T-doped device was obtained. The transient electroluminescence measurement as well as capacitance-voltage and impedance-voltage correlations were utilized to explore the factors governing the high efficiency and stability. The obtained results clearly show that the energy transfer and charge transport is highly efficient; they also show the photoelectric semiconducting characteristics of exciplex-based OLEDs, which are significantly different from those of unipolar host-based reference devices D3 (Alq₃: 1 wt % C545T) and D5 (CBP: 8 wt % Ir(ppy)₂(acac)). Our works have established a systematic protocol to shed light on the mechanisms behind exciplex-based devices. The combined results also confirm the bright prospect of the exciplex-forming system as the co-host for highly efficient and stable OLEDs.

Fully Coated Semitransparent Organic Solar Cells with a Doctor-Blade-Coated Composite Anode Buffer Layer of Phosphomolybdic Acid and PEDOT:PSS and a Spray-Coated Silver Nanowire Top Electrode

In the aim to realize high performance semitransparent fully coated organic solar cells, printable electrode buffer layers and top electrodes are two important key technologies. An ideal ink for the preparation of the electrode buffer layer for printed top electrodes should have good wettability and negligible solvent corrosion to the underlying layer. This work reports a novel organic-inorganic composite of phosphomolybdic acid (PMA) and PEDOT:PSS that features excellent wettability with the active layer and printed top Ag nanowires and high resistibility to solvent corrosion. This composite buffer layer can be easily deposited on a polymer surface to form a smooth, homogeneous film via spin-coating or doctor-blade coating. Through the use of this composite anode buffer layer, fully coated semitransparent devices with doctor-blade-coated functional layers and spray-coated Ag nanowire top electrodes showed the highest power conversion efficiency (PCE) of 5.01% with an excellent average visible-light transmittance (AVT) of 50.3%, demonstrating superior overall characteristics with a comparable performance to and a much higher AVT than cells based on a thermally evaporated MoO₃/Ag/MoO₃ thin film electrode (with a PCE of 5.77% and AVT of 19.5%). The current work reports the fabrication of fully coated inverted organic solar cells by combining doctor-blade coating and spray coating and, more importantly, demonstrates that a nanocomposite of a polyoxometalate and conjugated polymer could be an excellent anode buffer layer for the fully coated polymer solar cells with favorable interfacial contact, hole extraction efficiency, and high comparability with full printing.

Toward Environmentally Robust Organic Electronics: Approaches and Applications

Recent interest in flexible electronics has led to a paradigm shift in consumer electronics, and the emergent development of stretchable and wearable electronics is opening a new spectrum of ubiquitous applications for electronics. Organic electronic materials, such as π-conjugated small molecules and polymers, are highly suitable for use in low-cost wearable electronic devices, and their charge-carrier mobilities have now exceeded that of amorphous silicon. However, their commercialization is minimal, mainly because of weaknesses in terms of operational stability, long-term stability under ambient conditions, and chemical stability related to fabrication processes. Recently, however, many attempts have been made to overcome such instabilities of organic electronic materials. Here, an overview is provided of the strategies developed for environmentally robust organic electronics to overcome the detrimental effects of various critical factors such as oxygen, water, chemicals, heat, and light. Additionally, molecular design approaches to π-conjugated small molecules and polymers that are highly stable under ambient and harsh conditions are explored; such materials will circumvent the need for encapsulation and provide a greater degree of freedom using simple solution-based device-fabrication techniques. Applications that are made possible through these strategies are highlighted.

High efficiency quantum dot light emitting diodes from positive aging

Colloidal quantum dot-polymer hybrid light emitting diodes (QLEDs) that exhibit external quantum efficiencies >12% for all three primary colors (21% from green) have been demonstrated. These high efficiencies result in part from a positive aging effect reported here for the first time, where positive aging means the efficiency of the QLED increased with time. We have achieved 470 h operational life time (T₉₀) at 2550 nits for red QLEDs. At longer times, negative aging phenomena lead to lower luminance and limit the lifetime of the QLEDs. It is concluded that we have reasonable control over the efficiency of QLEDs. The next challenge is to achieve lifetimes sufficiently long for all three primary colors for applications such as in television and illumination.

Regular Organic Solar Cells with Efficiency over 10% and Promoted Stability by Ligand- and Thermal Annealing-Free Al-Doped ZnO Cathode Interlayer

Landmark power conversion efficiency (PCE) over 10% has been accomplished in the past year for single-junction organic solar cell (OSCs), suggesting a promising potential application of this technology. However, most of the high efficient OSCs are based on inverted configuration. Regular structure OSCs with both high efficiency and good stability are still rarely reported to date. In this work, by utilizing a new designed ligand-free and non-thermal-annealing-treated Al-doped ZnO cathode interlayer, high efficiency and greatly improved stability are simultaneously realized in regular OSCs. The highest PCE of 10.14% is accomplished for single-junction regular OSCs with active blend of poly [[2,6'-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophenediyl]] (PTB7-Th):[6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM). Excellent device stability is confirmed as well, by keeping 90% of its initial PCE value after 135 d in N₂, and 80% of its initial PCE value after 15 d in ambient air, respectively. Furthermore, the applicability of the designed interlayer in regular OSCs is demonstrated by other active blend systems, including the nonfullerene material. This work highlights that high efficiency and good stability can be realized simultaneously in regular OSCs as well, and will provide referential strategy and methodology for this target.

Statistical Paradigm for Organic Optoelectronic Devices: Normal Force Testing for Adhesion of Organic Photovoltaics and Organic Light-Emitting Diodes

In this study, we assess the utility of a normal force (pull-test) approach to measuring adhesion in organic solar cells and organic light-emitting diodes. This approach is a simple and practical method of monitoring the impact of systematic changes in materials, processing conditions, or environmental exposure on interfacial strength and electrode delamination. The ease of measurement enables a statistical description with numerous samples, variant geometry, and minimal preparation. After examining over 70 samples, using the Weibull modulus and the characteristic breaking strength as metrics, we were able to successfully differentiate the adhesion values between 8-tris(hydroxyquinoline aluminum) (Alq₃) and poly(3-hexyl-thiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) interfaces with Al and between two annealing times for the bulk heterojunction polymer blends. Additionally, the Weibull modulus, a relative measure of the range of flaw sizes at the fracture plane, can be correlated with the roughness of the organic surface. Finite element modeling of the delamination process suggests that the out-of-plane elastic modulus for Alq₃ is lower than the reported in-plane elastic values. We suggest a statistical treatment of a large volume of tests be part of the standard protocol for investigating adhesion to accommodate the unavoidable variability in morphology and interfacial structure found in most organic devices.

Surface Energy and Work Function Control of AlOx/Al Surfaces by Fluorinated Benzylphosphonic Acids

The performance of organic electronic devices can be significantly improved by modifying metal electrodes with organic monolayers, which alter the physical and chemical nature of the interface between conductor and semiconductor. In this paper we examine a series of 12 phosphonic acid compounds deposited on the native oxide layer of aluminum (AlOx/Al), an electrode material with widespread applications in organic electronics. This series includes dodecylphosphonic acid as a reference and 11 benzylphosphonic acids, seven of which are fluorinated, including five newly synthesized derivatives. The monolayers are experimentally characterized by contact angle goniometry and by X-ray photoemission spectroscopy (XPS), and work function data obtained by low-intensity XPS are correlated with molecular dipoles obtained from DFT calculations. We find that monolayers are formed with molecular areas ranging from 17.7 to 42.9 Å(2)/molecule, and, by the choice of appropriate terminal groups, the surface energy can be tuned from 23.5 mJ/m(2) to 70.5 mJ/m(2). Depending on the number and position of fluorine substituents on the aromatic rings, a variation in the work function of AlOx/Al substrates over a range of 0.91 eV is achieved, and a renormalization procedure based on molecular density yields a surprising agreement of work function changes with interface dipoles as expected from Helmholtz' equation. The ability to adjust energetics and adhesion at organic semiconductor/AlOx interfaces has immediate applications in devices such as OLEDs, OTFTs, organic solar cells, and printed organic circuits.

Interplay between Interfacial Structures and Device Performance in Organic Solar Cells: A Case Study with the Low Work Function Metal, Calcium

A better understanding of how interfacial structure affects charge carrier recombination would benefit the development of highly efficient organic photovoltaic (OPV) devices. In this paper, transient photovoltage (TPV) and charge extraction (CE) measurements are used in combination with synchrotron radiation photoemission spectroscopy (SRPES) to gain insight into the correlation between interfacial properties and device performance. OPV devices based on PCDTBT/PC71BM with a Ca interlayer were studied as a reference system to investigate the interfacial effects on device performance. Devices with a Ca interlayer exhibit a lower recombination than devices with only an Al cathode at a given charge carrier density (n). In addition, the interfacial band structures indicate that the strong dipole moment produced by the Ca interlayer can facilitate the extraction of electrons and drive holes away from the cathode/polymer interface, resulting in beneficial reduction in interfacial recombination losses. These results help explain the higher efficiencies of devices made with Ca interlayers compared to that without the Ca interlayer.

The combined effect of mechanical strain and electric field cycling on the ferroelectric performance of P(VDF-TrFE) thin films on flexible substrates and underlying mechanisms

In this manuscript, we study the combined effect of mechanical strain and electric field cycling on the ferroelectric properties and polarization fatigue of P(VDF-TrFE) based flexible thin film capacitors from the perspective of flexible memory applications.

Quantum Chemical Insight into the LiF Interlayer Effects in Organic Electronics: Reactions between Al Atom and LiF Clusters

It is well known that the aluminum cathode performs dramatically better when a thin lithium fluoride (LiF) layer inserted in organic electronic devices. The doping effect induced by the librated Li atom via the chemical reactions producing AlF3 as byproduct was previously proposed as one of possible mechanisms. However, the underlying mechanism discussion is quite complicated and not fully understood so far, although the LiF interlayer is widely used. In this paper, we perform theoretical calculations to consider the reactions between an aluminum atom and distinct LiF clusters. The reaction pathways of the Al-(LiF)n (n = 2, 4, 16) systems were discovered and the energetics were theoretically evaluated. The release of Li atom and the formation of AlF3 were found in two different chemical reaction routes. The undissociated Al-(LiF)n systems have chances to change to some structures with loosely bound electrons. Our findings about the interacted Al-(LiF)n systems reveal new insights into the LiF interlayer effects in organic electronics applications.

Reversible degradation in ITO-containing organic photovoltaics under concentrated sunlight

Stabilities of ITO-containing and ITO-free organic solar cells were investigated under simulated AM 1.5G illumination and under concentrated natural sunlight.

Hybrid integrated label-free chemical and biological sensors

Label-free sensors based on electrical, mechanical and optical transduction methods have potential applications in numerous areas of society, ranging from healthcare to environmental monitoring. Initial research in the field focused on the development and optimization of various sensor platforms fabricated from a single material system, such as fiber-based optical sensors and silicon nanowire-based electrical sensors. However, more recent research efforts have explored designing sensors fabricated from multiple materials. For example, synthetic materials and/or biomaterials can also be added to the sensor to improve its response toward analytes of interest. By leveraging the properties of the different material systems, these hybrid sensing devices can have significantly improved performance over their single-material counterparts (better sensitivity, specificity, signal to noise, and/or detection limits). This review will briefly discuss some of the methods for creating these multi-material sensor platforms and the advances enabled by this design approach.

Band-bending in organic semiconductors: the role of alkali-halide interlayers

Band-bending in organic semiconductors, occurring at metal/alkali-halide cathodes in organic-electronic devices, is experimentally revealed and electrostatically modeled. Metal-to-organic charge transfer through the insulator, rather than doping of the organic by alkali-metal ions, is identified as the origin of the observed band-bending, which is in contrast to the localized interface dipole occurring without the insulating buffer layer.