Transparent Electrodes Research Articles

Flexible Short-Wave Infrared Transparent Electrode Based on Broadband Induced Transmission Mechanism

Flexible Short-Wave Infrared Transparent Electrode Based on Broadband Induced Transmission Mechanism

Recent Advances in Carbon Nanotube Utilization in Perovskite Solar Cells: A Review

Due to their exceptional optoelectronic properties, halide perovskites have emerged as prominent materials for the light-absorbing layer in various optoelectronic devices. However, to increase device performance for wider adoption, it is essential to find innovative solutions. One promising solution is incorporating carbon nanotubes (CNTs), which have shown remarkable versatility and efficacy. In these devices, CNTs serve multiple functions, including providing conducting substrates and electrodes and improving charge extraction and transport. The next iteration of photovoltaic devices, metal halide perovskite solar cells (PSCs), holds immense promise. Despite significant progress, achieving optimal efficiency, stability, and affordability simultaneously remains a challenge, and overcoming these obstacles requires the development of novel materials known as CNTs, which, owing to their remarkable electrical, optical, and mechanical properties, have garnered considerable attention as potential materials for highly efficient PSCs. Incorporating CNTs into perovskite solar cells offers versatility, enabling improvements in device performance and longevity while catering to diverse applications. This article provides an in-depth exploration of recent advancements in carbon nanotube technology and its integration into perovskite solar cells, serving as transparent conductive electrodes, charge transporters, interlayers, hole-transporting materials, and back electrodes. Additionally, we highlighted key challenges and offered insights for future enhancements in perovskite solar cells leveraging CNTs.

Ecofriendly cellulose substrate based flexible transparent electrode for flexible organic solar cells with efficiency over 18%

Flexibility is a key advantage of organic solar cells (OSCs), and the power conversion efficiencies (PCEs) of flexible OSCs (FOSCs) are primarily constrained by flexible transparent electrodes (FTEs). While much attention has been devoted to the study of conductive layers on FTEs, the importance of flexible substrates in influencing the properties of FTEs and the performance of FOSCs is often overlooked. In this study, we have developed an FTE using an eco‐friendly ethyl cellulose (EC) substrate and silver nanowires (AgNWs) as the conductive electrode. The FTE exhibits a high transmittance of up to 88% at 550 nm and a low sheet resistance of 17.65 Ω/□. Consequently, FOSCs based on the EC/PI FTEs achieved a remarkable PCE of 18.05%, comparable to that on the rigid ITO substrate. The flexible devices also demonstrated excellent bending and peeling durability even under extreme bending conditions.This article is protected by copyright. All rights reserved.

Interface Reactive Sputtering of Transparent Electrode for High-Performance Monolithic and Stacked Perovskite Tandem Solar Cells.

Sputtered indium tin oxide (ITO) fulfills the requirements of the top transparent electrodes (TTEs) in semitransparent perovskite solar cells (PSCs) and stacked tandem solar cells (TSCs) as well as the recombination layers in monolithic TSCs. However, the high-energy ITO particles will cause damage to the devices and reduce the photovoltaic performance. Herein, the interface reactive sputtering strategy has been proposed and implemented to construct cost-effective TTEs with high transmittance and excellent carrier transporting ability, aiming to realize high-performance semitransparent and tandem PSCs. Polyethylenimine (PEI) was chosen as the interface reactant, of which abundant amino groups on PEI can react with sputtered ITO nanoparticles so that coordination compounds can be formed during the ITO deposition process, facilitating the carrier transport at the interface of C60/PEI/ITO. Besides, the impact force of energetic ITO particles is greatly alleviated, and the intactness of the underlying C60 layer and perovskite layer is guaranteed. Thus, the prepared semitransparent subcells achieve a significantly enhanced power conversion efficiency (PCE) of 19.17%, surpassing those based on C60/ITO (11.64%). Moreover, the PEI-based devices demonstrate excellent storage stability, which maintains 98% of their original PCEs after 2000 hours. On the strength of the interface reactive sputtering ITO electrode, we successfully fabricated a stacked all-perovskite TSC with a PCE of 26.89% and a monolithic perovskite-organic TSC with a PCE of 24.33%. This work has provided a facile and instrumental solution for rendering TTEs function well in semitransparent and tandem PSCs. This article is protected by copyright. All rights reserved.

All‐Printed Electrically Driven Lighting via Electrochemiluminescence

AbstractElectrochemiluminescence (ECL) has attracted significant attention as a promising light‐emitting technology owing to its simple configuration and solution processability. ECL has wide applications in biological and chemical sensors, lighting, and displays. ECL lighting devices are fabricated as sandwiched structures with a transparent electrode on top, which limits their widespread adoption. Intricate structures with high precision and customizable designs can be directly fabricated using 3D printing. However, 3D printing of ECL devices is challenging because of poor printability and structural integrity of ECL luminophore inks. Here, all‐printed electrically driven lighting is demonstrated using the direct ink writing method. The ECL reactive layer and electrodes are directly printed using a side‐by‐side electrode configuration. A 3D printable ECL ink is developed by incorporating silica nanoparticles as rheological modifiers to realize well‐defined patterns with high structural integrity. Graphene is introduced on Ag multilayer electrodes to embrace both the electrical conductivity and electrochemical stability for efficient ECL operation. This all‐printing approach allows the fabrication of ECL devices with complex designs, such as combs and spirals. Moreover, it facilitates seamless printing on various substrate materials, making this technology an asset in the fields of biology, chemistry, and electronics.

Research Progress of Semi-Transparent Perovskite and Four-Terminal Perovskite/Silicon Tandem Solar Cells

Perovskite/silicon tandem solar cells are of great interest due to their potential for breaking the Shockley-Queisser limit of single-junction silicon solar cells. Perovskite solar cells are widely used as the top subcells in perovskite/silicon tandem solar cells due to their high efficiency and lower fabrication cost. Herein, we review the semi-transparent perovskite solar cell in terms of the mechanisms of their translucent structure, transparent electrodes, charge transport layer, and component modification. In addition, recent progress in the research and development of 4T perovskite/silicon tandem solar cells is summarized, with emphasis on the influence of perovskite structure and silicon cells on the progress of tandem solar cells. Finally, we discuss the challenges associated with 4T perovskite/silicon tandem solar cells and suggest directions for the development of perovskite/silicon commercialization.

Recent Progress in Semitransparent Organic Solar Cells: Photoabsorbent Materials and Design Strategies

The increasing energy demands of the global community can be met with solar energy. Solution-processed organic solar cells have seen great progress in power conversion efficiencies (PCEs). Semitransparent organic solar cells (ST-OSCs) have made enormous progress in recent years and have been considered one of the most promising solar cell technologies for applications in building-integrated windows, agricultural greenhouses, and wearable energy resources. Therefore, through the synergistic efforts of transparent electrodes, engineering in near-infrared photoabsorbent materials, and device engineering, high-performance ST-OSCs have developed, and PCE and average visible transmittance reach over 10% and 40%, respectively. In this review, we present the recent progress in photoabsorbent material engineering and strategies for enhancing the performance of ST-OSCs to help researchers gain a better understanding of structure–property–performance relationships. To conclude, new design concepts in material engineering and outlook are proposed to facilitate the further development of high-performance ST-OSCs.

A comprehensive study on transparent conducting oxides in compact microbial fuel cells: Integrated spectroscopic and electrochemical analyses for monitoring biofilm growth

Microbial fuel cells (MFCs) are an emerging technology that holds promise for renewable energy production and the mitigation of environmental challenges. This research paper introduces a single-compartment MFC reactor that utilizes transparent conducting oxides (TCOs), such as fluorine-doped tin oxide (FTO) and indium tin oxides (ITO), as the working electrodes. The effectiveness of MFCs based on FTO and ITO was evaluated by characterizing the transparent electrode and examining its performance during biofilm cultivation. Additionally, the optical properties of the biofilm grown directly on these electrodes were investigated using LEDs as a light source. The impressive average current density of 200 μA cm−2 over 100 days demonstrates the efficiency of the see-through electrodes in bioenergy extraction. The correlation between spectroscopic and microscopic analyses substantiates the feasibility of employing transparent electrodes for accurate quantification of biofilm thickness, with an initial accuracy of ±10 μm in the initial cycle, ±22 μm in the subsequent cycle, and a maximum of ±31 μm after seven days of growth. This innovative approach holds great potential for advancing our understanding of MFCs and their application in environmentally friendly energy generation and optical-based monitoring.

Empowering Zero‐Energy Buildings with Cutting‐Edge Self‐Powered Electrochromic Smart Window Technology

The development of energy‐efficient window technology is crucial for zero‐energy building approaches, as windows play a pivotal role in minimizing heat loss, optimizing natural light utilization, and contributing to overall energy conservation. In this study, a self‐powered electrochromic smart window is presented together and its application as a self‐charging battery is showcased. The self‐powered system is composed of a WOx electrochromic working electrode, an Al counter electrode, and an AlCl3 liquid electrolyte similar to a voltaic cell. This device generates an open circuit voltage of around 0.95 V. When two electrodes are connected, this voltage is applied as an external voltage and changes the color of the transparent WOx electrode into a blue state with approximately 62% transmittance modulation. However, if the two electrodes are connected via an light‐emitting diode (LED), the LED lights up for up to 4 h.

The Role of Device Architecture and Interfacial Layer on Performance of Semitransparent Organic Solar Cells

Semitransparent organic solar cells (ST‐OSCs) generally suffer from voltage loss in comparison to their opaque counterparts. Herein, ST‐OSCs constructed with conventional and inverted structures have been explored. The voltage losses of the inverted ST‐OSCs are lower than that of the conventional architectures when the thicknesses of the top transparent electrodes approach the percolation threshold, which is attributed to the larger surface energy of the bottom seeding layers, higher built‐in electric fields, and lower recombination losses. Moreover, ST‐OSCs with conventional architectures based on four commonly used electrode transporting layers (ETLs) PDINN, PDINO, PNDIT‐F3N, and PFN‐Br are employed to distinguish the Voc variation when capping with 10 nm top electrodes. It is revealed that ETL with larger surface energy and a stronger ability to reduce the cathode work function is more beneficial for reducing the voltage loss for ST‐OSCs. This work demonstrates the crucial role of device structure and interfacial layers in optimizing the ST‐OSC device performance.

Overcoming Challenges in OLED Technology for Lighting Solutions

In academic research, OLEDs have exhibited rapid evolution thanks to the development of innovative materials, new device architectures, and optimized fabrication methods, achieving high performance in recent years. The numerous advantages that increasingly distinguish them from traditional light sources, such as a large and customizable emission area, color tunability, flexibility, and transparency, have positioned them as a promising candidate for various applications in the lighting market, including the residential, automotive, industrial, and agricultural sectors. However, despite these promising attributes, the widespread industrial production of OLEDs encounters significant challenges. Key considerations center around efficiency and lifetime. In the present review, after introducing the theoretical basis of OLEDs and summarizing the main performance developments in the industrial field, three crucial aspects enabling OLEDs to establish a competitive advantage in terms of performance and versatility are critically discussed: the quality and stability of the emitted light, with a specific focus on white light and its tunability; the transparency of both electrodes for the development of fully transparent and integrable devices; and the uniformity of emission over a large area.

Graphene films grown by chemical vapor deposition and their applications

In this article we provide the results of the synthesis of graphene films and discuss their potential applications in electronic structures. Graphene films were synthesized on copper foil using the CVD method at 1050 °C. During the initial stage of synthesis, graphene domains with hexagonal shapes and an average size of 10 μm were formed. The orientation and size of the graphene domains are based on the synthesis parameters and the copper foil. As the synthesis time increases, domain cross-linking occurs, resulting in polycrystalline continuous graphene film formation. Graphene films have areas up to 100 cm2 and thicknesses ~ 1 nm to 5 nm. To measure the Raman spectra, graphene films were transferred to SiO2/Si substrates. Graphene films exhibit an intense 2D peak that significantly exceeds the G peak of crystalline graphite. Flexible transparent conductive touch panels were created on the basis of the grown graphene films. A lamination method has been used to create graphene films that can be transferred from copper foil to polymer substrates. A laboratory touch screen with a graphene film acting as a capacitive touch sensor was constructed on the basis of the transferred film, and transparent electrodes for molybdenum disulfide-based photosensitive elements were also created. Resistive humidity sensors based on graphene films were developed and transferred to SiO2/Si and epoxy/Si substrates. The graphene humidity sensor has a low response, high temperature stability, and is highly reliable.

A New Method for Evaluating the Influence of Coatings on the Strength and Fatigue Behavior of Flexible Glass

AbstractFlexible glass is an interesting substrate for a variety of displays, especially bendable or foldable ones, as it shows excellent surface properties and appealing haptics. With the necessary skill, flexible glass can be coated with thin films of different functionality, such as electrical or optical thin films, using plasma processes. In displays, thin film coatings such as transparent conductive electrodes and/or antireflective layer stacks are of major importance. Despite its attractive surface properties, however, flexible glass is still brittle, and its strength must be examined and monitored during any functionalization process, especially with regard to the fatigue behaviour. Currently, specific setups for cyclic fatigue testing of coated flexible glass are not available. Therefore, a new test method is presented herein for easy-to-handle rapid strength and fatigue testing using an endurance testing machine. This method overcomes two issues with the commonly used two-point bending test: the correct insertion of specimens is much easier, and both strength and fatigue testing using the same setup are now possible. Finite element method (FEM) simulation outcomes and first experimental simple fracture tests show that results comparable to those with a two-point bending test setup can be achieved with less effort. This makes it possible to analyze the fracture behaviour of flexible glass under cyclic loading and to evaluate the influence of thin film stress and other coating properties on its performance. Graphical Abstract

Synergistic Enhancement of Efficient Perovskite/Quantum Dot Tandem Solar Cells Based on Transparent Electrode and Band Alignment Engineering

AbstractPerovskite‐based tandem solar cells have demonstrated high potential for overcoming the Shockley–Queisser limit. Routine bandgap (RBG, ≈1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite‐based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four‐terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near‐infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum‐doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, ≈0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi‐transparent perovskite solar cells, the four‐terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics.

Controlled Fabrication of Composite Transparent Electrodes for Semitransparent Perovskite Solar Cells with above 84% Fill Factor

In the quest to develop efficient semitransparent perovskite solar cells (ST‐PSCs), the primary challenge lies in transparent electrode fabrication. n–i–p‐type ST‐PSCs often suffer from low fill factors (FF) and power conversion efficiency (PCE), attributed to the undesirable buffer layer/transparent conductive oxide combination of the transparent electrode. In this context, this study proposes an efficient composite transparent electrode (CTE) system comprising an ultrathin MoO3 buffer layer (5 nm) and low‐power sputtered indium zinc oxide (45 W–220 nm). The electrode demonstrates excellent compatibility with Spiro‐OMeTAD‐based devices, effectively addressing the low FF and PCE challenges of ST‐PSCs. Employing the new CTE, the best‐performing ST‐PSCs with the absorption edge at 1.57 eV achieve a remarkable PCE of 21.96% with an FF of up to 83.80%. More transparent ST‐PSCs with thickness‐modulated absorbers and average transmittance of 50.77% at 600–1200 nm wavelength result in a PCE of up to 20.91% with the highest known FF of 84.02%. This study presents a general and viable approach for fabricating efficient ST‐PSCs.

High-performance composite transparent electrode composed of ultra-long silver nanowires and antimony-doped tin oxide nanoparticles

Abstract Composite transparent conductive electrodes (TCEs) consisting of silver nanowires (AgNWs) and conductive metal oxides are very promising for flexible optoelectronic devices due to their smooth surface morphology and high chemical stability. However, it is still challenging to ensure high optoelectronic performance and long-term stability in practical applications. Here, we solved these problems by coating antimony-doped tin oxide (ATO) nanoparticles dispersion on ultra-long AgNWs network using waterborne polyurethane (WPU) binder. Ultra-long nanowires occupy less wire-wire junctions and space than short nanowires, thus increasing the optoelectronic performance and flexibility of the composite TCE. WPU improves the adhesion and stability of ATO nanoparticles to the substrate and AgNWs network. The fabricated composite TCE showed a low sheet resistance of 11.9 Ω/sq, good optical transmittance of 83% at 550 nm and a figure of merit (FOM) of 162 compared to PET/ITO electrode. It also showed excellent mechanical flexibility, adhesion to the substrate and solvent stability. Furthermore, the long-term conductivity was maintained under ambient conditions for 60 days.

Silver Nanowires (AgNWs) Post-Treatment Effect in Application of Flexible Transparent and Conductive Electrodes: A Mini Review

Transparent flexible electrodes (TFEs) are extremely crucial for expanding flexible and wearable electronic devices. Silver nanowires (AgNWs) have been extensively investigated as an alternative to replace Indium Tin Oxide (ITO) as a commercial TFE due to their high conductivity, transparency, and flexibility. AgNWs have replaced ITO-based electrodes as the preferred approach in flexible, transparent, and conductive electrodes (FTCE). AgNWs outperform other materials, such as Reduced Graphene Oxide (RGO), ceramic material, Carbon Nanotubes (CNT), and conductive polymers, in terms of electrical conductivity, transmittance, flexibility, and low sheet resistance. Numerous techniques, including as electrospinning, spray coating, spin coating, and doctor blades, are used to use AgNWs as flexible substrates. Seed-based growth and template-assisted synthesis are two fundamental synthesis techniques that could be used to generate AgNWs. However, poor adhesiveness, and thermal and electrical stability, begin to be bottlenecks for AgNWs as high deployment in a variety of devices. So AgNWs synthesis process began to shift to other methods, such as wet chemical and polyol. In this paper, short and clear summary of various advances including post-treatment methods such as UV radiation, microwave, sonication, quenching, and so on is conducted to be one step forward to test mechanical properties and to improve AgNWs performance.

A novel dual-functional flexible dimming film for smart window applications: Energy saving and self-cleaning performance

Polymer dispersed liquid crystal (PDLC) is a promising candidate for electrically controlled smart window applications because of its energy efficiency, convenience and other advantages. However, its flexibility and heat management capabilities are not effectively evaluated. Herein, a flexible dual-functional intelligent window based on PDLC composite is designed for this purpose, which integrates Ag nanowires as a transparent conductive electrode (TCE) and Tm3+/Yb3+-CsxWO3 (Tm3+/Yb3+-CWO) as a near-infrared shielding and air purification layer. Specifically, the as-made smart window can control the transmission of both visible and near-infrared light. Furtherly, it also possesses self-cleaning capability. A series of characterization has been carried out. The resistance of the Ag nanowire layer is measured to be 22.47 Ω/sq and the transmittance reaches 78.8 %. Flexibility test shows that when the bending radius is 4 mm, the resistance value of the TCE changes only 6 % after 500 repetitions, indicating good flexibility and stability. The spectrum examination reveals that the near-infrared light shielding efficiency achieves 80 % and the average transmittance of visible light is 76.7 %. The degradation of Rhodamine B (RhB) is used to evaluate the purification performance and result shows that the degradation percentage reaches 70 % in 120 min. Heat-regulation simulation test discloses that the indoor temperature can be decreased by 10 °C. Compared to traditional PDLC windows, the designed flexible window has broader application prospects in areas of architecture, vehicle glass, military stealth materials and so on.

Single‐ and Double‐Layer Embedded Metal Meshes for Flexible, Highly Transparent Electromagnetic Interference Shielding

AbstractSimulation and experimental studies are carried out on single‐layer and double‐layer embedded metal meshes (SLEMM and DLEMM) to assess their performance as transparent electromagnetic interference (EMI) shielding. The structures consist of silver meshes embedded in polyethylene terephthalate (PET). As a transparent electrode, SLEMMs exhibit a transparency of 82.7% and a sheet resistance of 0.61 Ωsq−1 as well as 91.0% and 1.49 Ωsq−1. This performance corresponds to figures of merit of 3101 and 2620, respectively. The SLEMMs achieve 48.0 dB EMI shielding efficiency (SE) in the frequency range of 8–18 GHz (X‐ and Ku‐bands) with 91% visible transmission and 56.2 dB EMI SE with 82.7% visible transmission. Samples exhibit stable performance after 1000 bending cycles with a radius of curvature of 4 mm and 60 tape test cycles. DLEMMs consist of fabricating SLEMM on opposite sides of the substrate where the distance can be varied using a spacer. Simulations are performed to investigate how varying spacer distance between two layers of metal meshes influences the EMI SE. DLEMMs are fabricated and achieved an EMI SE of 77.7 dB with 81.7% visible transmission. SLEMMs and DLEMMs may have a wide variety of applications in aerospace, medical, and military applications.

High Aspect Ratio Silver Nanogrids by Bottom-Up Electrochemical Growth as Transparent Electrode.

A scalable selective-area electrochemical method is reported for the fabrication of interconnected metal nanostructures. In this work, the fabrication of silver nanowire grids for the application of transparent electrodes is explored. The presented method is based on a through-the-mask electrodeposition method, where the mask is made by using substrate conformal imprint lithography. We find that the nucleation density of the silver nanoparticles is the key parameter for successful homogeneous void-free filling of the template. We independently controlled the density of the silver nuclei and their growth by using a double potential pulse. The silver nanowire grids show high transmission (95.9%) and low sheet resistance (as low as 3.7 Ω/sq), resulting in a superior figure of merit (FoM). Due to the bottom-up nature of this technique, arbitrarily high aspect ratio nanowires can be achieved, therefore decreasing the sheet resistance without affecting transmittance and carrier collection. The presented method can be generalized to the large-area nanofabrication of any well-defined nanostructure design of any metal transparent electrode for multiple applications.