Highly Conductive and Transparent PEDOT:PSS Films with a Fluorosurfactant for Stretchable and Flexible Transparent Electrodes

Highly conductive and transparent poly‐(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) films, incorporating a fluorosurfactant as an additive, have been prepared for stretchable and transparent electrodes. The fluorosurfactant‐treated PEDOT:PSS films show a 35% improvement in sheet resistance (R_s) compared to untreated films. In addition, the fluorosurfactant renders PEDOT:PSS solutions amenable for deposition on hydrophobic surfaces, including pre‐deposited, annealed films of PEDOT:PSS (enabling the deposition of thick, highly conductive, multilayer films) and stretchable poly(dimethylsiloxane) (PDMS) substrates (enabling stretchable electronics). Four‐layer PEDOT:PSS films have an R_s of 46 Ω per square with 82% transmittance (at 550 nm). These films, deposited on a pre‐strained PDMS substrate and buckled, are shown to be reversibly stretchable, with no change to R_s, during the course of over 5000 cycles of 0 to 10% strain. Using the multilayer PEDOT:PSS films as anodes, indium tin oxide (ITO)‐free organic photovoltaics are prepared and shown to have power conversion efficiencies comparable to that of devices with ITO as the anode. These results show that these highly conductive PEDOT:PSS films can not only be used as transparent electrodes in novel devices (where ITO cannot be used), such as stretchable OPVs, but also have the potential to replace ITO in conventional devices.     

A Universal Method of Producing Transparent Electrodes Using Wide‐Bandgap Materials

A UV light‐emitting diode (LED) is an eco‐friendly optical source with diverse applications. However, currently, the external quantum efficiency (EQE) of AlGaN‐based UV LEDs, particularly in the UV‐C band (<280 nm), is very low (<11%) mainly due to a large optical absorption via p‐GaN contact layers. A direct Ohmic contact to p‐AlGaN layers should be obtained using UV‐transparent conductive electrodes (TCEs) to solve this problem. A universal method is presented here to make such contact using electrical breakdown, with wide‐bandgap materials, to form conductive filaments (CFs), providing a current path between the TCEs and the p‐(Al)GaN layers. The contact resistance between the TCEs and the p‐GaN layers (or p‐AlGaN) is found to be on the order of 10^?5 Ω cm² (or 10^?3 Ω cm²), while optical transmittance is maintained up to 95% for AlN‐based TCEs at 250 nm. These findings could be a critical turning point delivering a breakthrough in UV LED technologies.     

Achieving High Efficiency and Improved Stability in ITO‐Free Transparent Organic Light‐Emitting Diodes with Conductive Polymer Electrodes

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.     

透明导电氧化物薄膜的新进展

透明导电氧化物（TCO）薄膜In2O3:Sn和SnO2:F都已经发展成熟，分别大规模应用于平板显示器和建筑两大领域。最近几年，TCO薄膜的研究又进入了一次复兴时期，研究和开发出几类具有明显特色的新型TCO薄膜。ZnO基TCO薄膜有替代In2o3:Sn薄膜的趋势；多元TCO薄膜材料可以调整其性能来满足某些特殊应用的需求；具有高载流子迁移率的In2O3：Mo薄膜为进一步提高TCO薄膜的性能打开了一条新路；真正的p型TCO薄膜为制造透明电子元器件迈出了第一步。     

Highly Robust Indium‐Free Transparent Conductive Electrodes Based on Composites of Silver Nanowires and Conductive Metal Oxides

A hybrid approach for the realization of In‐free transparent conductive layers based on a composite of a mesh of silver nanowires (NWs) and a conductive metal‐oxide is demonstrated. As metal‐oxide room‐temperature‐processed sol–gel SnO_x or Al:ZnO prepared by low‐temperature (100 °C) atomic layer deposition is used, respectively. In this concept, the metal‐oxide is intended to fuse the wires together and also to “glue” them to the substrate. As a result, a low sheet resistance down to 5.2 Ω sq^‐1 is achieved with a concomitant average transmission of 87%. The adhesion of the NWs to the substrate is significantly improved and the resulting composites withstand adhesion tests without loss in conductivity. Owing to the low processing temperatures, this concept allows highly robust, highly conductive, and transparent coatings even on top of temperature sensitive objects, for example, polymer foils, organic devices. These Indium‐ and PEDOT:PSS‐free hybrid layers are successfully implemented as transparent top‐electrodes in efficient all‐solution‐processed semitransparent organic solar cells. It is obvious that this approach is not limited to organic solar cells but will generally be applicable in devices which require transparent electrodes.     

Highly Conductive and Environmentally Stable Organic Transparent Electrodes Laminated with Graphene

Improving the lifetime and the operational and thermal stability of organic thin‐film materials while maintaining high conductivity and mechanical flexibility is critical for flexible electronics applications. Here, it is reported that highly conductive and environmentally stable organic transparent electrodes (TEs) can be fabricated by mechanically laminating poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) films containing dimethylsulfoxide and Zonyl fluorosurfactant (PDZ films) with a monolayer graphene barrier. The proposed lamination process allows graphene to be coated onto the PDZ films uniformly and conformally with tight interfacial binding, free of wrinkles and air gaps. The laminated films exhibit an outstanding room‐temperature hole mobility of ≈85.1 cm² V^?1 s^?1 since the graphene can serve as an effective bypass for charge carriers. The significantly improved stability of the graphene‐laminated TEs against high mechanical/thermal stress, humidity, and ultraviolet irradiation is particularly promising. Furthermore, the incorporation of the graphene barrier increases the expected lifetime of the TEs by more than two orders of magnitude.     

Stretchable and Transparent Conductive PEDOT:PSS‐Based Electrodes for Organic Photovoltaics and Strain Sensors Applications

The development of transparent, conducting, and stretchable poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐based electrodes using a combination of a polyethylene oxide (PEO) polymer network and the surfactant Zonyl is reported. The latter improves the ductility of PEDOT:PSS and enables its deposition on hydrophobic surfaces such as polydimethylsiloxane (PDMS) elastomers, while the presence of a 3D matrix offers high electrical conductivity, elasticity, and mechanical recoverability. The resulting electrode exhibits attractive properties such as high electrical conductivity of up to 1230 S cm^?1 while maintaining high transparency of 95% at 550 nm. The potential of the electrode technology is demonstrated in indium‐tin‐oxide (ITO)‐free solar cells using the PBDB‐T‐2F:IT‐4F blend with a power conversion efficiency of 12.5%. The impact of repeated stretch‐and‐release cycles on the electrical resistance is also examined in the effort to evaluate the properties of the electrodes. The interpenetrated morphology of the PEDOT:PSS and polyethylene oxide network is found to exhibit beneficial synergetic effects resulting in excellent mechanical stretchability and high electrical conductivity. By carefully tuning the amount of additives, the ability to detect small changes in electrical resistance as a function of mechanical deformation is demonstrated, which enables the demonstration of stretchable and resilient on‐skin strain sensors capable of detecting small motions of the finger.     

Ultrathin Metal films for Transparent Electrodes of Flexible Optoelectronic Devices

The need for the development of transparent conductive electrodes (TCEs) supported on flexible polymer substrates has explosively increased in response to flexible polymer‐based photovoltaic and display technologies; these TCEs replace conventional indium tin oxide (ITO) that exhibits poor performance on heat‐sensitive polymers. An efficient, flexible TCE is required to exhibit high electrical conductance and high optical transmittance, as well as excellent mechanical flexibility and long‐term stability, simultaneously. Recent advances in technologies utilizing an ultrathin noble‐metal film in a dielectric/metal/dielectric structure, or its derivatives, have attracted attention as promising alternatives that can satisfy the requirements of flexible TCEs. This review will survey the background knowledge and recent updates of synthetic strategies and design rules toward highly efficient, flexible TCEs based on ultrathin metal films, with a special focus on the principal features and available methodologies involved in the fabrication of highly transparent, conductive, ultrathin noble‐metal films. This survey will also cover the practical applications of TCEs to flexible organic solar cells and light‐emitting diodes.     

离子辅助沉积掺铝氧化锌透明导电膜的研究

报道了采用离子辅助电子枪蒸发技术制备优质氧化锌透明导电膜的工艺和结果,分析了源掺杂,镀膜气氛,衬底温度等参数与膜的电导率及透光特性的关系,作出了电阻率低达2×10     

采用不同透明电极的非晶铟镓锌氧化物薄膜晶体管

采用透明材料ITO和AZO为源漏电极,在室温下利用射频磁控溅射方法制作了底栅结构的非晶铟镓锌氧化物薄膜晶体管。实验发现,制备的薄膜晶体管均表现出了良好的开关特性。其中采用AZO为电极的薄膜晶体管的场效应迁移率为1.95cm2/V.s,开关比为4.53×105,在正向偏压应力测试下,阈值电压的漂移量为4.49V。     

ZnSnO/AgNW双层透明电极的制备及性能研究

利用旋涂银纳米线和磁控溅射ZnSnO薄膜相结合的方法,实现了高性能ZnSnO/AgNW双层透明电极的制备。采用X射线衍射仪和扫描电子显微镜对电极的结构和形貌进行了表征分析,利用紫外可见分光光度计和四探针测试仪分别对ZnSnO/AgNW双层透明电极的电学和光学性能进行了表征。结果表明,制备的ZnSnO/AgNW双层透明电极具有优异的电学和光学性能,在透过率为88.1%时,其方阻为12.3Ω/□,品质因子高达231。在5.0 mm的曲率半径下,对ZnSnO/AgNW双层透明电极进行了1 000次弯曲测试,其电阻仅增加了13%,表明ZnSnO/AgNW双层透明电极具有优异的柔性性能。此外,ZnSnO/AgNW双层透明电极经过20次胶带粘附测试和高温高湿测试后,方阻都基本保持不变,这说明ZnSnO/AgNW双层透明电极具有优异的粘附性以及抗氧化性。     

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.     

高价态差掺杂氧化物透明导电薄膜的研究

在实用的透明导电氧化物 (TCO)薄膜中 ,载流子迁移率主要是受电子与掺杂离子之间散射的限制。如果掺杂离子与氧化物中被替代离子的化合价相差较大 ,每个掺杂离子可以提供较多的自由载流子 ,则使用较少的掺杂量就可以获得足够多的自由载流子 ,而且可以获得较高的载流子迁移率和减少薄膜对可见光的吸收 ,是提高 TCO薄膜性能的一条捷径。采用反应蒸发法制备的掺钼氧化铟(In2 O3:Mo,简称 IMO)薄膜中 ,Mo6 +与 In3+的化合价态相差 3,远大于广泛研究和应用的 TCO薄膜材料 In2 O3:Sn、Sn O2 :F和 Zn O:Al中的价态差。IMO薄膜的电阻率可以低至 1.7× 10 - 4 Ω· cm,对 4μm以上波长红外线的反射率和可见光区域的平均透射率 (含 1.2 mm厚玻璃基底 )都高于 80 % ;载流子迁移率高达 80～ 130cm2 V- 1 s- 1 ,远超过其它掺杂 TCO薄膜 ;但是自由载流子浓度只有 2 .5× 10 2 0～ 3.5× 10 2 0 cm- 3,还有很大的发展空间可以进一步提高性能     

透明导电薄膜对太阳能平板集热器性能的影响

在介绍透明导电薄膜光学性质的基础上,分别讨论了不同情况下,太阳能平板集热器盖板采用镀有透明导电薄膜的玻璃对集热器的光热转换效率和保温性能的影响。结果表明,当集热器吸热板表面没有覆盖选择性吸收涂层,在盖板玻璃下表面镀有透明导电薄膜可以在一定温度范围内提高集热器的转换效率和保温性能,而当吸热板已覆盖有选择性吸收涂层时,盖板玻璃再镀透明导电薄膜,集热器辐射热损则减少很少,甚至不足以补偿由于玻璃透过率降低而增加的光反射损失,在这种情况下,盖板不宜再采用镀有透明导电薄膜的玻璃。     

Patterned Transparent Conductive Au Films through Direct Reduction of Gold Thiocyanate

Construction of structurally defined, patterned metal films is a fundamental objective in the emerging and active field of bottom‐up nanotechnology. A new strategy for constructing macroscopically organized Au nanostructured films is presented. The approach is based upon a novel phenomenon in which incubation of water‐soluble Au(SCN)₄^1? complex with amine‐displaying surfaces gives rise to spontaneous crystallization and concurrent reduction, resulting in the formation of patterned metallic gold films. The Au films exhibit unique nanoribbon morphology, likely corresponding to aurophilic interactions between the complex moieties anchored to the amine groups through electrostatic attraction. Critically, no external reducing agents are needed to initiate or promote formation of the metallic Au films. In essence, the thiocyanate ligands provide the means for surface targeting of the complex, guide the Au crystallization process and, importantly, donate the reducing electrons. It is shown that the Au films exhibit electrical conductivity and high transparency over a wide spectral range, lending the new approach to possible applications in optoelectronics, catalysis, and sensing. In a broader context, a new gold chemistry route is presented in which ligand‐enabled crystallization/reduction could open the way to a wealth of innovative reaction pathways and applications.     

Optically Transparent and Mechanically Robust Ionic Hydrogel Electrodes for Bright Electroluminescent Devices Achieving High Stretchability Over 1400%

To realize wearable displays and interactive soft robots, significant research efforts are focused on developing highly deformable alternating-current electroluminescent (ACEL) devices. Although soft emission layers are well developed, designing stretchable, conductive, and transparent soft electrodes remains challenging. In this study, ionic hydrogels are prepared comprising a double network (DN) of poly(N-hydroxyethylacrylamide-co-acrylamide)/crosslinked chitosan swollen in aqueous lithium bis(trifluoromethanesulfonyl) imide. Owing to the finely tuned DN structure of the polymeric crosslinker and transparent electrolyte, the developed ionic hydrogels exhibit remarkable stretchability (1400%), excellent optical transmittance (>99%), and high conductivity (1.95 × 10⁻² Sm⁻¹). Based on the high performance of the ionic hydrogels, ACEL devices are fabricated with an emission layer containing phosphor microparticles and demonstrate stable, high luminance under extreme deformation, and ultra-high elongation. The excellent transparency of the ionic hydrogel further enables the fabrication of novel soft ACEL devices with tandem structures by stacking several emission and electrode layers, in which each emission layer is independently controlled with a switch circuit.     

Electrohydrodynamic NanoDrip Printing of High Aspect Ratio Metal Grid Transparent Electrodes

The transparent conducting electrode is an essential component in many contemporary and future devices, ranging from displays to solar cells. Fabricating transparent electrodes requires a balancing act between sufficient electrical conductivity and high light transmittance, both affected by the involved materials, fabrication methodology, and design. While metal films possess the highest conductivity at room temperature, a decent optical transmittance can only be achieved with ultrathin films. Structuring the metal into optically invisible nanowires has been shown to be promising to complement or even substitute transparent conductive oxides as dominant transparent electrode material. Here the out‐of‐plane fabrication capability of the recently developed method of electrohydrodynamic NanoDrip printing to pattern gold and silver nanogrids with line widths from 80 to 500 nm is demonstrated. This fully additive process enables the printing of high aspect ratio nanowalls and by that significantly improves the electrical performance, while maintaining the optical transmittance at a high level. Metal grid transparent electrodes optimized for low sheet resistances (8 Ω sq^?1 at a relative transmittance of 94%) as well as optimized for high transmittance (97% at a sheet resistance of 20 Ω sq^?1) are reported, which can be tailored on demand for the use in various applications.