Particulate Coatings with Optimized Haze Properties

The haze factor, which describes the fraction of light that is scattered when passing through a transparent material, is of general importance for any optical device, from milk glass shielding visibility while providing ambient lighting to solar cells that are optimized by sophisticated light management layers. Often, such active layers are fabricated from particulate materials that are deposited as thin films on a substrate. Here, the effect of structural arrangement, position, and orientation of particles on the resulting haze factor is investigated. A mathematical optimization model that iteratively alters the particle layer structure to maximize or minimize the haze factor for a range of optimization scenarios is designed. Colloidal self‐assembly techniques are then used to replicate typical particle structures found in the optimized designs and correlate the macroscopically measured haze values to the predictions of the optimization. The results indicate general design rules that control the haze value in particle layers. Non close‐packed structures with distributed scatterers and high degrees of order provide minimal haze values while chain‐like arrangements and small clusters maximize the haze of a particle layer. Finally, the findings are transferred to metal nanohole films as model transparent electrodes with controlled haze values.     

Titanium Nitride Modified Photoluminescence from Single Semiconductor Nanoplatelets

Titanium nitride (TiN) is an alternative plasmonic material that has the potential for visible and near‐infrared optical applications due to its distinct properties. Here, coupling effects between TiN nanohole array films and nearby excitonic emitters, semiconductor nanoplatelets (NPLs), are investigated using single particle spectroscopy. At the emission wavelength of the NPLs, the local field enhancement close to the surface of the TiN nanohole array films induces an increase in the radiative decay rates of the emitters by a factor of up to 2. This effect diminishes quickly as the distance between the TiN nanohole array films and emitters increases. At short wavelengths where the NPLs are excited, the TiN nanohole array films exhibit lossy dielectric characteristics. Local field modification at these wavelengths leads to a reduced local density of electromagnetic states, and hence the photoluminescence intensity of the emitters. This study shows the potential of TiN as an alternative plasmonic material for optoelectronic and photonic applications, especially in the long wavelength ranges.     

Tailoring of microstructure and optoelectronic properties of Aluminum doped Zinc Oxide changing gun tilt

The influence of gun tilt on microstructure and optoelectronic properties of ZnO:Al thin films deposited by magnetron sputtering onto transparent glass substrates was studied. The structural and morphological film properties were investigated according to the cathode angle that placed in confocal geometry configuration inside sputtering system. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) were used, respectively. Film microstructure was analyzed by high resolution transmission electron microscopy (HR-TEM). Results showed relevant changes in AZO film properties depending on gun tilt, fact that can affect the device performance. Rougher AZO surfaces with lower average transparency values in visible range and worse electrical properties were observed when gun tilt decreased. These strong dependences can be considered as important aspects when design suitable electrodes for optoelectronic devices. In this sense, the ability of tuning AZO film properties as function of geometrical deposition system configuration was evaluated. This approach would allow fabricating coatings based on the same raw material but different optoelectronic properties.     

Trilayer Nanomesh Films with Tunable Wettability as Highly Transparent,Flexible, and Recyclable Electrodes

Metallic mesh materials are promising candidates to replace traditional transparent conductive oxides such as indium tin oxide (ITO) that is restricted by the limited indium resource and its brittle nature. The challenge of metal based transparent conductive networks is to achieve high transmittance, low sheet resistance, and small perforation size simultaneously, all of which significantly relate to device performances in optoelectronics. In this work, trilayer dielectric/metal/dielectric (D/M/D) nanomesh electrodes are reported with precisely controlled perforation size, wire width, and uniform hole distribution employing the nanosphere lithography technique. TiO₂/Au/TiO₂ nanomesh films with small hole diameter (≤700 nm) and low thickness (≤50 nm) are shown to yield high transmittance (>90%), low sheet resistance (≤70 Ω sq^?1), as well as outstanding flexural endurance and feasibility for large area patterning. Further, by tuning the surface wettability, these films are applied as easily recyclable flexible electrodes for electrochromic devices. The simple and cost‐effective fabrication of diverse D/M/D nanomesh transparent conductive films with tunable optoelectronic properties paves a way for the design and realization of specialized transparent electrodes in optoelectronics.     

Optically Transparent,Ultrathin Pt Films as Versatile Metal Substrates for Molecular Optoelectronics

This contribution reports a simple, straightforward method (cool sputtering) of fabricating robust, homogeneous, conductive, and optically transparent ultrathin Pt films. Their morphological, structural, mechanical, electrical, and optical properties are reported. The morphology and structure of these Pt films are investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X‐ray diffraction. The ultrathin Pt films, approximately 20 nm thick, are characterized by a homogenous, polycrystalline structure, with a tendency to adopt a (111) texture upon the thermal treatment. Moreover, thermal treatment (annealing or flaming) of the as‐prepared films also substantially improves their chemical and mechanical robustness. F films behave as bulk Pt in terms of electrical resistivity and suitability as working electrodes in cyclic voltammetry experiments. Overall, the unique combination of these excellent features: homogeneity, robustness, and conductivity, in addition to the high optical transparency in the 300–800 nm range of the electromagnetic spectrum, make ultrathin Pt films appropriate for a variety of applications in the field of molecular optoelectronics. The formation of functional molecular self‐assembled monolayers (SAMs) on these transparent, conductive films allows their optical monitoring using transmission optical spectroscopy, as well as the probing of their electrical properties. The potential of such Pt films as suitable metal substrates in opto‐ and nanoelectronics is proven by representative applications, including switching of prototypical photochromic and electrochromic species in SAMs and molecule–metal junctions.     

Mechanical integrity of hybrid indium-free electrodes for flexible devices

Maintaining electrical conductivity, optical transparency, and mechanical integrity against bending and stretching are key requirements for flexible transparent electrodes. Transparent conducting oxides (TCOs) are widely used thin film electrodes in optoelectronic devices. However, these materials are brittle and reducing film thickness to improve their mechanical integrity compromises their electrical performance. Here we combine TCO thin films with metal grids embedded in a polymer substrate to create hybrid electrodes with low sheet resistance and high resilience to bending. Amorphous zinc tin oxide (ZTO) and aluminum-doped zinc oxide (AZO) films sputtered onto polyethylene-terephthalate (PET) substrates with and without embedded metal grids are studied. The hybrid electrodes have an optical absorptance below 5% in the visible range and their electrical sheet resistance is less than 1 Ω/sq. The critical strain for tensile failure is analyzed through a combination of electrical measurements and in-situ observations of crack initiation and propagation during tensile loading. The mean critical strain for failure of the AZO/metal grid is 8.5% and that of the ZTO/metal grid is as high as 10%. The AZO and ZTO films alone present critical strain values around 0.6% and 1% respectively, demonstrating that the addition of the metal grid considerably improves the resistance onset strain of the electrodes far beyond these critical strain limits.     

带有矩形孔阵列的Au-介质-Au多层膜的透射特性

周期性亚波长孔阵列的异常透射性质在亚波长光电器件设计中具有重要意义。两层或更多膜层上周期孔阵列结构,由于层之间电磁场的相互作用可以导致新的光学性质。利用时域有限差分方法理论研究了带有矩形孔阵列的Au-介质-Au多层膜的透射特性。结果表明:该结构在近红外波段的透射谱存在多个透射峰,并且透射峰的数量、位置和强度可以通过改变结构的几何参数和介质膜的材料进行调控。详细分析了介质膜的厚度和折射率、孔阵列的周期、矩形孔的边长等因素对多层膜矩形孔阵列透射谱的影响,为利用多个表面等离子共振设计多波长控制器件提供了一定的参考。     

Role of Polymeric Metal Nucleation Inducers in Fabricating Large‐Area,Flexible, and Transparent Electrodes for Printable Electronics

The advent of special types of transparent electrodes, known as “ultrathin metal electrodes,” opens a new avenue for flexible and printable electronics based on their excellent optical transparency in the visible range while maintaining their intrinsic high electrical conductivity and mechanical flexibility. In this new electrode architecture, introducing metal nucleation inducers (MNIs) on flexible plastic substrates is a key concept to form high‐quality ultrathin metal films (thickness ≈ 10 nm) with smooth and continuous morphology. Herein, this paper explores the role of “polymeric” MNIs in fabricating ultrathin metal films by employing various polymers with different surface energies and functional groups. Moreover, a scalable approach is demonstrated using the ionic self‐assembly on typical plastic substrates, yielding large‐area electrodes (21 × 29.7 cm²) with high optical transmittance (>95%), low sheet resistance (<10 Ω sq^?1), and extreme mechanical flexibility. The results demonstrate that this new class of flexible and transparent electrodes enables the fabrication of efficient polymer light‐emitting diodes.     

Large-Area Smooth Conductive Films Enabled by Scalable Slot-Die Coating of Ti3C2Tx MXene Aqueous Inks

Large-area flexible transparent conductive electrodes (TCEs) featuring excellent optoelectronic properties (low sheet resistance, R_s, at high transparency, T) are vital for integration in transparent wearable electronics (i.e., antennas, sensors, supercapacitors, etc.). Solution processing (i.e., printing and coating) of conductive inks yields highly uniform TCEs at low cost, holding great promise for commercially manufacturing of transparent electronics. However, to formulate such conductive inks as well as to realize continuous conductive films in the absence of percolation issue are quite challenging. Herein, the scalable slot-die coating of Ti₃C₂T_x MXene aqueous inks is reported for the first time to yield large-area uniform TCEs with outstanding optoelectronic performance, that is, average DC conductivity of 13 000 ± 500 S cm⁻¹. The conductive MXene nanosheets are forced to orientate horizontally as the inks are passing through the moving slot, leading to the rapid manufacturing of highly aligned MXene TCEs without notorious percolation problems. Moreover, through tuning the ink formulations, such conductive MXene films can be easily adjusted from transparent to opaque as required, demonstrating very low surface roughness and even mirror effects. These high-quality, slot-die-coated MXene TCEs also demonstrate excellent electrochemical charge storage properties when assembled into supercapacitors.     

掺钛氧化锌透明导电薄膜的制备及特性研究

利用直流磁控溅射法在室温水冷玻璃衬底上成功地制备出了掺钛氧化锌(ZnO:Ti)透明导电薄膜.研究了靶衬间距对ZnO:Ti薄膜结构、形貌和光电性能的影响.研究结果表明,靶衬间距对ZnO:Ti薄膜的结构和电阻率有显著影响.X射线衍射(XRD)表明,ZnO:Ti薄膜为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向.在靶衬间距为4.6 cm时,实验获得的ZnO:Ti薄膜电阻率具有最小值4.18×10-4Ω·cm.实验制备的ZnO:Ti薄膜具有良好的附着性能,可见光区平均透过率超过92%.ZnO:Ti薄膜可以用作薄膜太阳能电池和液晶显示器的透明电极.     

Structures for organic diode lasers and optical properties oforganic semiconductors under intense optical and electrical excitations

The challenges to realizing diode lasers based on thin films of organic semiconductors are primarily related to low charge carrier mobility in these materials. This not only limits the thickness of organic films to ⩽100 nm in electrically pumped devices, but it also leads to changes in the optical properties of organic films induced by the large number of carriers trapped in the materials subjected to an intense electrical excitation. We describe organic waveguide laser structures composed of thin organic films and transparent indium-tin-oxide electrodes. These waveguides allow for efficient injection of an electrical current into the organic layers and provide for low optical losses required in a laser. The changes in the optical properties of organic thin films induced by electrical excitation are studied using electroluminescence and pump and probe spectroscopy. Induced transparency and absorption observed in the organic materials may be related to triplet excitons or trapped charge carriers. Pump-induced absorption is also observed in organic films under quasi-CW optical excitation. These effects must be taken into account both in the design of organic diode laser structures and in the selection of charge transporting materials     

Room-Temperature Preparation of High-Transparency Low-Resistivity ITO Films by Ion Beam Sputtering

Low-temperature preparation of transparent conducting electrodes is essential for flexible optoelectronic devices. Tin-doped In₂O₃ films with high transparency and low electrical resistance were prepared at room temperature using a radiofrequency ion beam sputtering system. Specimens with a low sheet resistivity of 10⁻⁴ Ω cm and a high visible-light transmittance of 85% to 90% were obtained. Hall measurements were used to determine mobility and carrier concentration, and the effects on resistivity are discussed.     

Reduced Graphene Oxide Micromesh Electrodes for Large Area,Flexible, Organic Photovoltaic Devices

A laser‐based patterning technique—compatible with flexible, temperature‐sensitive substrates—for the production of large area reduced graphene oxide micromesh (rGOMM) electrodes is presented. The mesh patterning can be accurately controlled in order to significantly enhance the electrode transparency, with a subsequent slight increase in the sheet resistance, and therefore improve the tradeoff between transparency and conductivity of reduced graphene oxide (rGO) layers. In particular, rGO films with an initial transparency of ≈20% are patterned, resulting in rGOMMs films with a ≈59% transmittance and a sheet resistance of ≈565 Ω sq^?1, that is significantly lower than the resistance of ≈780 Ω sq^?1, exhibited by the pristine rGO films at the same transparency. As a proof‐of‐concept application, rGOMMs are used as the transparent electrodes in flexible organic photovoltaic (OPV) devices, achieving power conversion efficiency of 3.05%, the highest ever reported for flexible OPV devices incorporating solution‐processed graphene‐based electrodes. The controllable and highly reproducible laser‐induced patterning of rGO hold enormous promise for both rigid and flexible large‐scale organic electronic devices, eliminating the lag between graphene‐based and indium–tin oxide electrodes, while providing conductivity and transparency tunability for next generation flexible electronics.     

Built‐In Haze Glass‐Fabric Reinforced Siloxane Hybrid Film for Efficient Organic Light‐Emitting Diodes (OLEDs)

Substrates with high transmittance and high haze are desired for increasing the light outcoupling efficiency of organic light‐emitting diodes (OLEDs). However, most of the polymer films used as substrate have high transmittance and low haze. Herein, a facile route to fabricate a built‐in haze glass‐fabric reinforced siloxane hybrid (GFRH) film having high total transmittance (≈89%) and high haze (≈89%) is reported using the scattering effect induced by refractive index contrast between the glass fabric and the siloxane hybrid (hybrimer). The hybrimer exhibiting large refractive index contrast with the glass fabric is synthesized by removing the phenyl substituents. Besides its optical properties, the hazy GFRH films exhibit smooth surface (R_sq = 0.2 nm), low thermal expansion (13 ppm °C⁻¹), high chemical stability, and dimensional stability. Owing to the outstanding properties of the GFRH film, OLED is successfully fabricated onto the film exhibiting 74% external quantum efficiency enhancement. The hazy GFRH's unique optical properties, excellent thermal stability, outstanding dimensional stability, and the ability to perform as a transparent electrode enable them as a wide ranging substrate for the flexible optoelectronic devices.     

Controllable Fabrication of Transparent Macroporous Graphene Thin Films and Versatile Applications as a Conducting Platform

Graphene sheets have been demonstrated to be the building blocks for various assembly structures, which eventually determine the macroscopic properties of graphene materials. As a new assembly structure, transparent macroporous graphene thin films (MGTFs) are not readily prepared due to the restacking tendency of graphene sheets during processing. Here, an ice crystal‐induced phase separation process is proposed for preparation of transparent MGTFs. The ice crystal‐induced phase separation process exhibits several unique features, including efficient prevention of graphene oxide restacking, easy control on the transparency of the MGTFs, and wide applicability to substrates. It is shown that the MGTFs can be used as porous scaffold with high conductivity for electrochemical deposition of various semiconductors and rare metal nanoparticles such as CdSe, ZnO, and Pt, as well as successive deposition of different materials. Notably, the macroporous structures bestow the MGTFs and the nanoparticle‐decorated MGTFs (i.e., Pt@MGTF and CdSe@MGTF) enhanced performance as electrode for oxygen reduction reaction and photoelectrochemical H₂ generation.     

Microstructure and optoelectronic properties of gallium- titanium-zinc oxide thin films deposited by magnetron sputtering

Gallium-titanium-zinc oxide(GTZO) transparent conducting oxide(TCO) thin films were deposited on glass substrates by radio frequency magnetron sputtering. The dependences of the microstructure and optoelectronic properties of GTZO thin films on Ar gas pressure were observed. The X-ray diffraction(XRD) and scanning electron microscopy(SEM) results show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. With the increment of Ar gas pressure, the microstructure and optoelectronic properties of GTZO thin films will be changed. When Ar gas pressure is 0.4 Pa, the deposited films possess the best crystal quality and optoelectronic properties.     

High‐Performance Hazy Silver Nanowire Transparent Electrodes through Diameter Tailoring for Semitransparent Photovoltaics

Solution‐processed metal nanowire networks have attracted substantial attention as clear transparent conductive electrodes (TCEs) to replace metal oxides for low‐cost and flexible touch panels and displays. While targeting photovoltaic applications, TCEs are expected to be more hazy for enhancing light absorption in the active layer, but are still required to retain high transmittance and low sheet resistance. Balancing these properties (haze, transmittance, and conductivity) in TCEs to realize high performance but high haze simultaneously is a challenge because they are mutually influenced. Here, by precisely tailoring the diameter of thick–long silver nanowires using rapid radial electrochemical etching, high hazy flexible TCEs are fabricated with high figure of merit of up to 741 (4 Ω sq^?1 at 88.4% transmittance with haze of 13.3%), surpassing those of commercialized brittle hazy metal oxides and exhibiting superiority for photovoltaic applications. Laminating such TCEs onto the perovskite solar cells as top electrodes, the obtained semitransparent devices exhibit power efficiencies up to 16.03% and 11.12% when illuminated from the bottom and top sides, respectively, outperforming reported results based on similar device architecture. This study provides a simple strategy for flexible and hazy TCEs fabrication, which is compatible with mild solution‐processed photovoltaic devices, especially those containing heat‐sensitive or chemical‐sensitive materials.     

Enhanced flexibility and stability of PEDOT:PSS electrodes through interfacial crosslinking for flexible organic light-emitting diodes

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films have drawn extensive attention as one of the most promising flexible transparent conductive electrodes to replace traditional indium tin oxide. However, some critical issues, such as weak adhesion, vulnerability to moisture and detrimental acidic property, need to be addressed before the practical application and industrialization. Here, we propose a facile and effective strategy of interfacial crosslinking to further improve the flexibility and stability of PEDOT:PSS electrodes with high transparency and conductivity by introducing polyethyleneimine ethoxylated (PEIE) on the surface. The flexibility and stability of PEDOT:PSS electrodes with PEIE overcoating layer are significantly improved, which can be attributed to the interfacial crosslinking reaction between PEIE and PSS. Finally, flexible organic light-emitting didoes (OLEDs) are constructed based on the PEDOT:PSS electrodes modified by PEIE, and current efficiency is enhanced from 20.5 to 76.4 cd/A with a 2.7-fold enhancement, owning to the improved carrier balance. This study confirms that PEIE is effective in protecting the PEDOT:PSS films from mechanical damage and moisture attack, while maintaining the high conductive and transmittance, and illustrates a promising future in low-cost flexible optoelectronic devices employing PEDOT:PSS electrodes.     

Transparent metal oxide electrode CID imager

The use of metal oxide transparent conductive electrodes in a charge-injection device (CID) imaging array has resulted in a quantum efficiency of approximately 70 percent, uniform throughout the visible, with useful array response out to 3500 /spl Aring/. The advantages of using highly transparent metal oxide electrodes for the fabrication of frontside illuminated arrays is described. A new high density CID cell is described, which does not require any contact windows or diffused regions. This cell structure is simply composed of two crossed rows and column electrodes and is easily fabricated. Because no contacts are required, it can be reduced in size for large high density arrays. The results for a 32/spl times/32 self-scanned array are presented.     

Transparent metal oxide electrode CID imager

The use of metal oxide transparent conductive electrodes in a charge-injection device (CID) imaging array has resulted in a quantum efficiency of approximately 70 percent, uniform throughout the visible, with useful array response out to 3500 Å. The advantages of using highly transparent metal oxide electrodes for the fabrication of frontside illuminated arrays is described. A new high density CID cell is described, which does not require any contact windows or diffused regions. This cell structure is simply composed of two crossed rows and column electrodes and is easily fabricated. Because no contacts are required, it can be reduced in size for large high density arrays. The results for a 32 × 32 self-scanned array are presented.