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The performance of both organic light-emitting diodes (OLEDs) and organic solar cells (OSC) depends on efficient coupling between optical far field modes and the emitting/absorbing region of the device. Current approaches towards OLEDs with efficient light-extraction often are limited to single-color emission or require expensive, non-standard substrates or top-down structuring, which reduces compatibility with large-area light sources. Here, we report on integrating solution-processed nano-particle based light-scattering films close to the active region of organic semiconductor devices. In OLEDs, these films efficiently extract light that would otherwise remain trapped in the device. Without additional external outcoupling structures, translucent white OLEDs containing these scattering films achieve luminous efficacies of 46 lm W-1 and external quantum efficiencies of 33% (both at 1000 cd m-2). These are by far the highest numbers ever reported for translucent white OLEDs and the best values in the open literature for any white device on a conventional substrate. By applying additional light-extraction structures, 62 lm W-1 and 46% EQE are reached. Besides universally enhancing light-extraction in various OLED configurations, including flexible, translucent, single-color, and white OLEDs, the nano-particle scattering film boosts the short-circuit current density in translucent organic solar cells by up to 70%. [ABSTRACT FROM AUTHOR]

Micro-structured organic photovoltaic (OPV) devices on polyethylene terephthalate substrates are produced using direct laser interference patterning (DLIP). The performance of organic solar cells on these substrates is improved by a factor of 1.16, and a power conversion efficiency of 7.70% is achieved. We show that a shorter spatial period of the pattern allows for a stronger light trapping effect in solar cell, as it leads to a longer light path. Moreover, since the patterned structures are located on the outside of the fully encapsulated OPV devices, there are no problems with the roughness induced shunts. [ABSTRACT FROM AUTHOR]

(Received 2 March 2016; accepted 15 June 2016; published online 24 June 2016) The performance of organic optoelectronic devices can be improved by employing a suitable optical cavity design beyond the standard plane layer approach, e.g., by the inclusion of periodically or randomly textured structures which increase light incoupling or extraction. One of the simplest approaches is to add an additional layer containing light scattering particles into the device stack. Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films are promising for replacing the brittle and expensive indium tin oxide transparent electrode. We use a blend of 100 nm TiO2 scattering particles in PEDOT:PSS solution to fabricate transparent electrode films which also functions as a scattering layer. When utilized in an organic photovoltaic device, a power conversion efficiency of 7.92% is achieved, which is an 8.6% relative improvement compared to a device with a neat PEDOT:PSS electrode without the nanoparticles. This improvement is caused by an increase in short-circuit current due to an improved photon harvesting in the 320 nm-700 nm spectral wavelength range. [ABSTRACT FROM AUTHOR]

The degradation of sexithiophene cascade organic solar cells is studied. Glass–glass encapsulated devices on indium tin oxide as transparent electrode show efficiencies of 6.6% and degrade within 500 h in illuminated 38 °C/50% RH climate. Fully flexible devices with silver nanowire electrode and alumina barrier achieve 5% efficiency and degrade within 30 h due to electrode failure. [ABSTRACT FROM AUTHOR]

We measure basic network parameters of silver nanowire (AgNW) networks commonly used as transparent conducting electrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistance RNW of a single nanowire shows a value of RNW = (4.9±60.18)Ω/µm. The junction resistance RJ differs for annealed and non-annealed NW networks, exhibiting values of RJ = (25.2±1.9)Ω (annealed) and RJ = (529±239)Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistance RS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20% (common RS 10Ω/sq). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries. [ABSTRACT FROM AUTHOR]

Thin, transparent silver films sandwiched between dielectric layers are a versatile and high performance transparent electrode technology. Using direct laser interference patterning (DLIP), we are able to structure thin metal films by direct ablation in a fast, single step process. To achieve beneficial pattern and ablation properties, different sublayers of MoOx, Au, Al, Cr, or organics below the silver film and different laser power densities and pulse numbers are investigated. The resulting hexagonally periodic array of apertures shows improved transmittance and sheet resistance. For the best parameter set, the silver network contains little superfluous material at the joints and benefits from partial recrystallization, improving the conductivity. The nanostructured thin-films have great potential to be combined with dielectric antireflection layers as transparent electrode for any thin-film optoelectronic devices. [ABSTRACT FROM AUTHOR]

Pulsed laser deposited gallium doped zinc oxide (ZnO:Ga) is reported as transparent top electrode for organic solar cells. In contrast to standard coating techniques, prone to harm organic sublayers and leading to strongly reduced device efficiencies, eclipse pulsed laser deposition (PLD) in argon atmosphere is identified as compatible, nonharmful deposition method for ZnO:Ga, even on top of sensitive organic material. Although PLD is not yet ready for mass production, the experiments reveal and solve crucial process limitations, e.g., droplet impacts, which might be useful also for high yield deposition methods. Optimized ZnO:Ga top electrodes achieve a high mean transparency in the visible spectral range of Tvis = 82.7% and a reasonable sheet resistance of RS = 83 Ω sq−1. The organic photovoltaic devices prepared with this electrode obtained an efficiency of η = 2.9%, almost equal to the efficiency of reference samples using a state-of-the-art metal top contact ( η = 3.0%). The investigations here demonstrate the successful deposition of transparent conductive oxides as top electrode for organic devices and open a new path towards the combination of metal oxides and organic semiconductors. [ABSTRACT FROM AUTHOR]

The article offers information on the use of hybrid electrodes with a combination of ultratransparent poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS) and an evaporated semitransparent silver (Ag) grid for small-molecule organic solar cells. Topics discussed include electrical and optical properties as well as excellent mechanical flexibility of indium-tin oxide (ITO), performance of Organic photovoltaic (OPV) cells and characteristics of various electrodes.

The article offers information on a study which examines ultratransparent poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)(PEDOT:PSS) and silver (Ag) grid hybrid electrodes for organic photovoltaic (OPV) cells. An oxygen plasma etching process was performed to prepare the PEDOT:PSS thin films. It shows the potential of hybrid electrodes for effective OPV cells.

Diffusion barrier stacks for the encapsulation of organic electronics made from inorganic nanolaminates of Al2O3 and TiO2 with aluminum alkoxide interlayers have been deposited by atomic layer deposition (ALD) and molecular layer deposition (MLD). As a part of the MLD process development, the deposition of aluminum alkoxide with low a density of about 1.7 g/cm³ was verified. The ALD/MLD diffusion barrier stack is meant to be deposited either on a polymer film, creating a flexible barrier substrate, or on top of a device on glass, creating a thin-film encapsulation. In order to measure the water vapor transmission rate (WVTR) through the barrier, the device is replaced by a calcium layer acting as a water sensor in an electrical calcium test. For the barrier stack applied as thin-film encapsulation on glass substrates, high resolution scanning electron microscopy investigations indicate that the inorganic nanolaminates without MLD interlayers are brittle as they crack easily upon the stress induced by the corroding calcium below. The introduction of up to three MLD interlayers of 12 nm each into the 48 nm barrier film laminate successfully mitigates stress issues and prevents the barrier from cracking. Using the three MLD interlayer configurations on glass, WVTRs of as low as 10-5 g/m²/d are measured at 38 °C and 32% relative humidity. On polymer barrier substrates, the calcium is evaporated onto the barrier stack and encapsulated with a cavity glass. In this configuration, the corroding calcium has space for expansion and gas release without affecting the underlying barrier film. In consequence, a WVTR of about 3 × 10-3 g/m²/d is measured for all samples independently of the number of MLD interlayers. In conclusion, a stabilization and preservation of the ALD barrier film against mechanical stress is achieved by the introduction of MLD interlayers into the inorganic nanolaminate. [ABSTRACT FROM AUTHOR]

Highly transparent electrodes are demonstrated based on thermally evaporated calcium:silver blend thin-films, which show unusually high transmission well above the expectations from bulk material properties and thin film optics. These electrodes exhibit a low sheet resistance of 27.3 Ω/, combined with an extraordinarily high mean transmittance of 93.0% in the visible spectral range (σdc/σopt = 186.7), superior to the commonly used inorganic electrodes made from indium tin oxide (ITO). Additionally, the metal blend electrode is flexible, showing a constant sheet resistance down to a bending radius of 10 mm and can be employed on top of organic devices without causing damage to the organic material. The spontaneously formed unique microstructure of a polycrystalline Ag network with randomly distributed nanoapertures, surrounded by a calcium shell, enables broadband transmittance enhancement due to amplified plasmonic coupling. Consequently, top-illuminated organic solar cells using such metal blend electrodes achieve a power conversion efficiency of 7.2% (which defines a new record for top illuminated organic solar cells) and even exceed the efficiency of similar bottom-illuminated reference solar cells (6.9%) employing common ITO electrodes. [ABSTRACT FROM AUTHOR]

Conventional planar organic light-emitting diodes (OLEDs) suffer from poor light extraction due to the total internal reflection at the waveguided interfaces. Therefore, the development of efficient light extraction structures is of great necessity and significance to realize practical applications in large area and cost-effective light sources. In this paper, a high-performance internal light outcoupling system for white OLEDs with spontaneously formed metal oxide nanostructures is developed. The fabrication process of the outcoupling system is simple and can be scaled to large area manufacturing. The enhancement of external quantum efficiency in white OLEDs comprising the outcoupling system reaches a factor of 1.7, and it is further increased to 2.9 when a hemispherical lens is employed. Together with the improvement of light extraction, excellent color stability over broad viewing angles is achieved. [ABSTRACT FROM AUTHOR]

The great potential of solution-processed metal nanowire networks utilized as a transparent electrode has attracted much attention in the last years. Typically, silver nanowires are applied, although their replacement by more abundant and cheaper materials is of interest. Here, a hydrazine-free synthesis route for high aspect ratio copper nanowires is used to prepare conductive networks showing an enhanced electrode performance. The network deposition is done with a scalable spray-coating process on glass and on polymer foils. By a pressing or an annealing step, highly conductive transparent electrodes are obtained, and they reveal transmittance-resistance values similar to indium tin oxide (ITO) and networks made of silver nanowires. The application potential of the copper nanowire electrodes is demonstrated by integrating them into an evaporated small-molecule organic solar cell with 3% efficiency. [ABSTRACT FROM AUTHOR]

Efficient transparent organic light-emitting diodes (OLEDs) with improved stability based on conductive, transparent poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes are reported. Based on optical simulations, the device structures are carefully optimized by tuning the thickness of doped transport layers and electrodes. As a result, the performance of PEDOT:PSS-based OLEDs reaches that of indium tin oxide (ITO)-based reference devices. The efficiency and the long-term stability of PEDOT:PSS-based OLEDs are significantly improved. The structure engineering demonstrated in this study greatly enhances the overall performances of ITO-free transparent OLEDs in terms of efficiency, lifetime, and transmittance. These results indicate that PEDOT:PSS-based OLEDs have a promising future for practical applications in low-cost and flexible device manufacturing. [ABSTRACT FROM AUTHOR]

High performance indium tin oxide (ITO)-free small molecule organic solar cells and organic light-emitting diodes (OLEDs) are demonstrated using optimized ZnO electrodes with alternative non-metallic co-dopants. The co-doping of hydrogen and fluorine reduces the metal content of ZnO thin films, resulting in a low absorption coefficient, a high transmittance, and a low refractive index as well as the high conductivity, which are needed for the application in organic solar cells and OLEDs. While the established metal-doped ZnO films have good electrical and optical properties, their application in organic devices is not as efficient as other alternative electrode approaches. The optimized ZnO electrodes presented here are employed in organic solar cells as well as OLEDs and allow not only the replacement of ITO, but also significantly improve the efficiency compared to lab-standard ITO. The enhanced performance is attributed to outstanding optical properties and spontaneously nanostructured surfaces of the ZnO films with non-metallic co-dopants and their straightforward integration with molecular doping technology, which avoids several common drawbacks of ZnO electrodes. The observations show that optimized ZnO films with non-metallic co-dopants are a promising and competitive electrode for low-cost and high performance organic solar cells and OLEDs. [ABSTRACT FROM AUTHOR]

The importance of O3 pulse duration for encapsulation of organic light emitting diodes (OLEDs) with ultra thin inorganic atomic layer deposited Al2O3 layers is demonstrated for deposition temperatures of 50 °C. X-ray reflectivity (XRR) measurements show that O3 pulse durations longer than 15 s produce dense and thin Al2O3 layers. Correspondingly, black spot growth is not observed in OLEDs encapsulated with such layers during 91 days of aging under ambient conditions. This implies that XRR can be used as a tool for process optimization of OLED encapsulation layers leading to devices with long lifetimes. [ABSTRACT FROM AUTHOR]

n‐Doped C60 is reported as a new electrode material for indium‐tin‐oxide‐free organic solar cells. All layers from the bottom to top electrode are prepared in one step in a vacuum chamber. The organic solar cells based on the n‐C60 electrodes assisted by a semitransparent metal grid exhibit efficiencies as high as 2.9%. [ABSTRACT FROM AUTHOR]

An innovative gold-silver top electrode with low sheet resistance and high transmittance is investigated for optical optimization of inverted top-emitting white OLEDs. Furthermore, a Molybdenum-oxide hole injection layer is applied, improving the electrical characteristics. We obtain highly efficient, angular stable, inverted white OLEDs with large tolerance to thickness variations. [ABSTRACT FROM AUTHOR]

We present highly transparent and conductive silver thin films in a thermally evaporated dielectric/metal/dielectric (DMD) multilayer architecture as top electrode for efficient small molecule organic solar cells. DMD electrodes are frequently used for optoelectronic devices and exhibit excellent optical and electrical properties. Here, we show that ultrathin seed layers such as calcium, aluminum, and gold of only 1 nm thickness strongly influence the morphology of the subsequently deposited silver layer used as electrode. The wetting of silver on the substrate is significantly improved with increasing surface energy of the seed material resulting in enhanced optical and electrical properties. Typically thermally evaporated silver on a dielectric material forms rough and granular layers which are not closed and not conductive below thicknesses of 10 nm. With gold acting as seed layer, the silver electrode forms a continuous, smooth, conductive layer down to a silver thickness of 3 nm. At 7 nm silver thickness such an electrode exhibits a sheet resistance of 19 Ω/□ and a peak transmittance of 83% at 580 nm wavelength, both superior compared to silver electrodes without seed layer and even to indium tin oxide (ITO). Top-illuminated solar cells using gold/silver double layer electrodes achieve power conversion efficiencies of 4.7%, which is equal to 4.6% observed in bottom-illuminated reference devices employing conventional ITO. The top electrodes investigated here exhibit promising properties for semitransparent solar cells or devices fabricated on opaque substrates. [ABSTRACT FROM AUTHOR]

Transparent conductive oxides and alternative transparent electrodes for organic photovoltaics and OLEDs Organic, photoactive devices, such as OLEDs or organic solar cells, currently use indium tin oxide (ITO) as transparent electrode. Whereas ITO is industry-proven for many years and shows very good electrical and optical properties, its application for lowcost and flexible devices might not be optimal. For such applications innovative technologies such as networkbased metal nanowire or carbon nanotube electrodes, graphene, conductive polymers, metal thin-films and alternative transparent conductive oxides emerge. Although some of these technologies are rather experimental and far from application, some of them have the potential to replace ITO in selected applications. [ABSTRACT FROM AUTHOR]

Abstract: We have developed semi-transparent n–i–p organic solar cells (OSC) with free-standing multi-wall carbon nanotube (f-CNT) sheets as transparent top electrodes. By a simple and damage-free room temperature orthogonal liquid solution assisted self-laminating process, f-CNT top electrodes are successfully deposited on top of ZnPc:C60 bulk heterojunction small molecule OSCs. The cells show high fill factors above 58% as well as efficiencies up to 1.5% and greater long-term stability compared to the device having a metal electrode. For the given cell structure with f-CNT semi-transparent electrodes, the influence of an optical spacer on light absorption is studied by a systematic variation of the hole transport layer thickness, supported by optical simulations. The results strongly indicate that OSCs with f-CNT top electrodes and optimized thin film stack are highly promising for semi-transparent OSCs, which can be used in tandem devices, in tinted smart windows, and similar applications by a simple and damage-free process in roll-to-roll configuration that can be scaled to large area manufacturing. [Copyright &y& Elsevier]

We demonstrate significant efficiency enhancement of ITO-free OLEDs by combining both the high-conductivity conducting polymer PEDOT: PSS as the transparent electrode and the solution-processed nano-composite scattering films as optical extraction layers. The external quantum efficiency (EQE) of ITO-free device can be significantly enhanced by a factor of 1.8 at 1000 cd/m2. [ABSTRACT FROM AUTHOR]

We report on efficient and stable ITO-free small molecule organic solar cells with conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes using a post-treatment process, causing selective removal of PSS. The solar cells with post-treated PEDOT:PSS electrodes show significantly improved short circuit current densities and efficiencies compared to untreated devices. Moreover, the removal of PSS by the post-treatment significantly improves the lifetime of devices, which are more resistant to loss of fill factor compared to untreated devices. [ABSTRACT FROM AUTHOR]

We demonstrate low-cost, efficient indium tin oxide (ITO)-free organic light-emitting diodes (OLEDs) with improved stability based on conductive, transparent poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes. The device structures are carefully optimized by tuning the thickness of doped transport layers and electrodes based on optical simulations. The performance of PEDOT:PSS-based OLEDs reaches that of ITO-based reference devices. Furthermore, we present efficient ITO-free white OLED based on internal light extraction system combined with the PEDOT:PSS electrodes. [ABSTRACT FROM AUTHOR]

A hybrid electrode with a combination of an ultratransparent conductive polymer (nearly 100% transparency) and a semitransparent silver grid is developed for organic photovoltaic cells. In article number 1401822, Yong Hyun Kim and co‐workers report that the hybrid electrode shows an improvement of the photovoltaic performance and a potential to reduce a significant resistive power loss in large‐area devices. These hybrid electrodes will contribute the development of low‐cost, efficient, large‐area organic photovoltaic cells. [ABSTRACT FROM AUTHOR]

The cover illustrates a flexible small molecule solar cell with three different semitransparent silverbased top electrodes using varying seed layers. With increasing surface energy of the seed layer, the wetting of subsequently deposited silver is significantly improved as indicated in the zoomed out SEM microscope images. For continuous and closed silver films, the transparency of the electrode, the optical field distribution inside the solar cell, and its power conversion efficiency are strongly increased. Further details can be found in the article by Sylvio Schubert and co‐workers on page 438. [ABSTRACT FROM AUTHOR]

Flexible aluminum moisture barrier films are shown to meet ultra-barrier requirements with water vapor transmission rates as low as 1*10 −4 g/m 2 /day at 38 °C and 90% R.H. These low transmission rates are achieved by lamination of two films that are independently processed on individual substrates. The integration in organic electronic devices like organic solar cells or OLEDs is particularly easy in a single lamination step, since an existing aluminum electrode can be utilized as one half of the moisture barrier. The resulting laminate maintains flexibility of the device and improves the barrier quality by an order of magnitude compared to conventional stacking of two barriers. Organic solar cells with this type of encapsulation are manufactured and aged in controlled climate. They do not exhibit significant extrinsic degradation. [ABSTRACT FROM AUTHOR]