RESUMEN

In fabricating functional layers, including thin-film transistors and conductive electrodes, using roll-to-roll (R2R) processing on polymer-based PET film, the instability of the slot-die coating meniscus under a high-speed web impedes functional layer formation with the desired thickness and width. The thickness profiles of the functional layers significantly impact the performance of the final products. In this study, we introduce an electrohydrodynamic (EHD)-based voltage application module to a slot-die coater to ensure the uniformity of the cross-machine direction (CMD) thickness profile within the functional layer and enable a stable, high-speed R2R process. The module can effectively control the spreadability of the meniscus by utilizing variations in the surface tension of the ink. The effectiveness of the EHD module was experimentally verified by applying a high voltage to a slot-die coater while keeping other process variables constant. As the applied voltage increases, the CMD thickness deviation reduces by 64.5%, and the production rate significantly increases (up to 300%), owing to the formation of a stable coated layer. The introduction of the EHD-based application module to the slot-die coater effectively controlled the spreadability of the meniscus, producing large-area functional layers.

RESUMEN

Morphological homogeneity and interfacial traps are essential issues to achieve high-efficiency and stable large-area organic solar cells (OSCs). Herein, by the investigation of three quinoxaline-based acceptors, i.e., PM6:Qx-1, PM6:Qx-2, and PM6:Qx-p-4Cl, the performance degradation in up-scaling OSCs is explored. The inhomogeneous morphology in PM6:Qx-2 induces a nonuniform spatial distribution of charge generation, showing a rapid decline in efficiency and stability in large-area OSCs. In comparison, the homogeneous morphology in PM6:Qx-1 and PM6:Qx-p-4Cl alleviates the stability drop. When utilizing 2-phenylethylmercaptan to fill the interfacial traps, the stability drop disappears for PM6:Qx-1 and PM6:Qx-p-4Cl, while it persists for PM6:Qx-2. The PM6:Qx-1 large-are device yields a high efficiency of 13.47% and superior thermal stability (T80 = 2888 h). Consequently, the interface modification dominates the performance degradation of large-area devices with homogeneous morphology, while it cannot eliminate the traps in inhomogeneous film. These results provide a clear understanding of degradation mechanisms in upscaling devices.

RESUMEN

Slot die coating is a widely used technique for the production of high accuracy films. One of the main challenges in slot die coating processes is determining the optimal range of operating parameters to prevent defects, such as bubbles, in high-viscosity films. In this study, both simulation and experimental methods were used to investigate the changes in the upstream meniscus under various coating parameters. Two types of air entrainment processes were considered, dominated by fluid inertia and viscous force. The formation of anticlockwise and clockwise vortex flows near the bottom of the upstream meniscus was found to alter the apparent dynamic contact angle of the upstream meniscus, leading to fluctuations in the apparent dynamic contact angle within a range of 70°-75° to 135°-140°. These fluctuations eventually resulted in air entrainment. This research is important for improving the quality and efficiency of slot die coating processes.

RESUMEN

Polymer thin films with a cross-web gradient structure is a burgeoning area of research, having received more attention in the last two decades, for improvements in the performance and material properties. Such patterned films have been fabricated using several techniques, but in practice these techniques are non-scalable, material-dependent, wasteful, and not highly efficient. Slot die coating, a well-known scalable manufacturing process, is used to fabricate gradient polymer thin films which will be investigated herein. By incorporating slot die with the custom roll-to-roll imaging system, gradient thin films are successfully fabricated by forcing two fluidic materials into the slot die simultaneously and by manipulating the viscous, diffusive, and inertial forces. The materials will be allowed to intermix, with the aim of having approximately a 50% mix along the centerline of any two contiguous stripes. Moreover, several characterizations such as FTIR, UV-vis spectroscopy, and SEM are performed to assess the quality of the gradient polymer thin films. The gradient structure fabricated using functional and nonfunctional materials has successfully improved the functional properties compared to fully blended two materials. This work will provide an understanding of the mechanisms to obtain gradient polymer thin-film structures that exhibit the desired geometric structure and performance.

RESUMEN

The performance of large-area perovskite solar cells (PSCs) has been assessed for typical compositions, such as methylammonium lead iodide (MAPbI3 ), using a blade coater, slot-die coater, solution shearing, ink-jet printing, and thermal evaporation. However, the fabrication of large-area all-inorganic perovskite films is not well developed. This study develops, for the first time, an eco-friendly solvent engineered all-inorganic perovskite ink of dimethyl sulfoxide (DMSO) as a main solvent with the addition of acetonitrile (ACN), 2-methoxyethanol (2-ME), or a mixture of ACN and 2-ME to fabricate large-area CsPbI2.77 Br0.23 films with slot-die coater at low temperatures (40-50 °C). The perovskite phase, morphology, defect density, and optoelectrical properties of prepared with different solvent ratios are thoroughly examined and they are correlated with their respective colloidal size distribution and solar cell performance. The optimized slot-die-coated CsPbI2.77 Br0.23 perovskite film, which is prepared from the eco-friendly binary solvents dimethyl sulfoxide:acetonitrile (0.8:0.2 v/v), demonstrates an impressive power conversion efficiency (PCE) of 19.05%. Moreover, the device maintains ≈91% of its original PCE after 1 month at 20% relative humidity in the dark. It is believed that this study will accelerate the reliable manufacturing of perovskite devices.

RESUMEN

We investigated triple-halide perovskite (THP) absorber layers with 5 mol % MAPbCl3 added to the double-halide perovskite (Cs0.22FA0.78)Pb(I0.85Br0.15)3. As a deposition method, a highly scalable printing technique, slot-die coating, with a subsequent annealing step was used. We found a strong power conversion efficiency (PCE) dependence of the corresponding solar cells on the annealing temperature. The device performance deteriorated when increasing the annealing temperature from 125 to 170 °C, mainly via losses in the open-circuit voltage (Voc) and in the fill factor (FF). To understand the mechanisms behind this performance loss, extensive characterizations were performed on both, the THP thin films and the completed solar-cell stacks, as a function of annealing temperature. Correlative scanning electron microscopy analyses, i.e., electron backscatter diffraction, energy-dispersive X-ray spectroscopy, and cathodoluminescence, in addition to X-ray diffraction and photoluminescence, confirmed the presence of PbI2 platelets on the surface of the THP thin films. Moreover, the area fraction of the PbI2 platelets on the film surface increased with increasing annealing temperature. The deteriorated device performance when the annealing temperature is increased from 125 to 170 °C is explained by the increased series resistance and increased interface recombination caused by the PbI2 platelets, leading to decreased Voc and FF values of the solar-cell devices. Thus, the correlative analyses provided insight into microscopic origins of the efficiency losses.

RESUMEN

A roll-to-roll manufacturing system performs printing and coating on webs to mass-produce large-area functional films. The functional film of a multilayered structure is composed of layers with different components for performance improvement. The roll-to-roll system is capable of controlling the geometries of the coating and printing layers using process variables. However, research on geometric control using process variables is limited to single-layer structures only. This study entails the development of a method to proactively control the geometry of the upper coated layer by using the lower-layer coating process variable in the manufacture of a double-coated layer. The correlation between the lower-layer coating process variable and upper coated layer geometry was examined by analyzing the lower-layer surface roughness and spreadability of the upper-layer coating ink. The correlation analysis results demonstrate that tension was the dominant variable in the upper coated layer surface roughness. Additionally, this study found that adjusting the process variable of the lower-layer coating in a double-layered coating process could improve the surface roughness of the upper coating layer by up to 14.9%.

RESUMEN

Energy shortage has become a global issue in the twenty-firt century, as energy consumption grows at an alarming rate as the fossil fuel supply exhausts. Perovskite solar cells (PSCs) are a promising photovoltaic technology that has grown quickly in recent years. Its power conversion efficiency (PCE) is comparable to that of traditional silicon-based solar cells, and scale-up costs can be substantially reduced due to its utilization of solution-processable fabrication. Nevertheless, most PSCs research uses hazardous solvents, such as dimethylformamide (DMF) and chlorobenzene (CB), which are not suitable for large-scale ambient operations and industrial production. In this study, we have successfully deposited all of the layers of PSCs, except the top metal electrode, under ambient conditions using a slot-die coating process and nontoxic solvents. The fully slot-die coated PSCs exhibited PCEs of 13.86% and 13.54% in a single device (0.09 cm2) and mini-module (0.75 cm2), respectively.

RESUMEN

Carbazole- and fluorene-substituted benzidine blocks have been functionalized with two different solubilizing pendant groups, in order to enhance the material's solubility in greener solvents. Preserving the optical and electrochemical properties, the aromatic function and substitution showed an important influence on the solvent affinity, achieving concentrations up to 150 mg/mL in o-xylenes for the glycol-containing materials and decent solubility in alcohols for the compounds functionalized with ionic chains. The latter solution proved to be ideal for the preparation of luminescence slot-die coating film on top of flexible-substrates up to 33 cm×2 cm. As a proof of concept, the materials have been implemented in different organic electronic devices, highlighting the low turn-on voltage (4 V) presented by organic light-emitting diodes (OLEDs), which is comparable with vacuum-processed devices. A structure-solubility relationship and a synthetic strategy are disentangled in this manuscript to tailor organic semiconductors and adapt their solubility towards the desired solvent and application.

RESUMEN

Homogeneous and pinhole-free large-area perovskite films are required to realize the commercialization of perovskite modules and panels. Various large-area perovskite coatings were developed; however, at their film coating and drying stages, many defects were formed on the perovskite surface. Consequently, not only the devices lost substantial performance but also their long-term stability deteriorated. Here, we fabricated a compact and uniform large-area MAPbI3-perovskite film by a slot-die coater at room temperature (T) and at high relative humidity (RH) up to 40%. The control slot-die-coated perovskite solar cell (PSC) produced 1.082 V open-circuit voltage (Voc), 24.09 mA cm-2 short current density (Jsc), 71.13% fill factor (FF), and a maximum power conversion efficiency (PCE) of 18.54%. We systematically employed a multi-functional artificial amino acid (F-LYS-S) to modify the perovskite defects. Such amino acids are more inclined to bind and adhere to the perovskite defects. The amino, carbonyl, and carboxy functional groups of F-LYS-S interacted with MAPbI3 through Lewis acid-base interaction and modified iodine vacancies significantly. Fourier transform infrared spectroscopy revealed that the C═O group of F-LYS-S interacted with the uncoordinated Pb2+ ions, and X-ray photoelectron spectroscopy revealed that the lone pair of -NH2 coordinated with the uncoordinated Pb2+ and consequently modified the I- vacancies remarkably. As a result, the F-LYS-S-modified device demonstrated more than three-fold charge recombination resistance, which is one of the primary requirements to fabricate high-performance PSCs. Therefore, the device fabricated employing F-LYS-S demonstrated remarkable PCE of 21.08% with superior photovoltaic parameters of 1.104 V Voc, 24.80 mA cm-2 Jsc, and 77.00%. FF. Concurrently, the long-term stability of the PSCs was improved by the F-LYS-S post-treatment, where the modified device retained ca. 89.6% of its initial efficiency after storing for 720 h in air (T ∼ 27 °C and RH ∼ 50-60%).

RESUMEN

The power conversion efficiency (PCE) of the state-of-the-art large-area slot-die-coated perovskite solar cells (PSCs) is now over 19%, but issues with their stability persist owing to significant intrinsic point defects and a mass of surface imperfections introduced during the fabrication process. Herein, the utilization of a hydrophobic all-organic salt is reported to modify the top surface of large-area slot-die-coated methylammonium (MA)-free halide perovskite layers. Bearing two molecules, each of which is endowed with anchoring groups capable of exhibiting secondary interactions with the perovskite surfaces, the organic salt acts as a molecular lock by effectively binding to both anion and cation vacancies, substantially enhancing the materials' intrinsic stability against different stimuli. It not only reduces the ingression of external species such as oxygen and moisture, but also suppresses the egress of volatile organic components during the thermal stability testing. The treated PSCs demonstrate efficiency of 19.28% (active area of 58.5 cm2 ) and 17.62% (aperture area of 64 cm2 ) for the corresponding mini-module. More importantly, unencapsulated slot-die-coated mini-modules incorporating the all-organic surface modifier show ≈80% efficiency retention after 7500 h (313 days) of storage under 30% relative humidity (RH). They also remarkably retain more than 90% of the initial efficiency for over 850 h while being measured continuously.

RESUMEN

Slot-die coating is recognized as the most compatible method for the roll-to-roll (R2R) processing of large-area flexible organic solar cells (OSCs). However, the photovoltaic performance of large-area flexible OSC lags significantly behind that of traditional spin-coating devices. In this work, two acceptors, Qx-1 and Qx-2, show quite different film-formation kinetics in the slot-die coating process. In situ absorption spectroscopy indicates that the excessive crystallinity of Qx-2 provides early phase separation and early aggregation, resulting in oversized crystal domains. Consequently, the PM6:Qx-1-based 1 cm2 flexible device exhibits an excellent power conversion efficiency (PCE) of 13.70%, which is the best performance among the slot-die-coated flexible devices; in contrast, the PM6:Qx-2 blend shows a pretty poor efficiency, which is lower than 1%. Moreover, the 30 cm2 modules based on PM6:Qx-1, containing six 5 cm2 sub-cells, exhibit a PCE of 12.20%. After being stored in a glove box for over 6000 h, the PCE remains at 103% of its initial values, indicating excellent shelf stability. Therefore, these results show a promising future strategy for the upscaling fabrication of flexible large-area OSCs.

RESUMEN

Sustainable processing solvents, photoactive materials, and scalable manufacturing will play a key role in commercializing printed organic photovoltaics (OPVs). The record-breaking pioneering OPV reports have done an outstanding job in accelerating the discovery of champion photoactive materials and device engineering practices; however, these works predominantly involve health-hazardous halogenated processing solvents/additives and non-scalable thin-film coating methods. Herein, large-area slot-die-manufactured OPV cells from eco-friendly halogen-free solvents and synthetically scalable materials are showcased. All the four layers; electron transport layer (SnO2), cathode interlayer (PDIN-H), bulk-heterojunction (BHJ, PTQ-10:BTP-4F-12), and hole transport layer [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate) (PEDOT:PSS] are slot-die-coated in air. A non-halogenated co-solvent mixture of toluene and 2-methyl tetrahydrofuran is presented as an optimal processing solvent to realize the high-quality thin films of PTQ10:BTP-4F-12. The unencapsulated champion solar cells characterized in ambient conditions (RH = 30%, T = 22 °C) exhibit power conversion efficiencies (PCEs) of 12.1 and 17.8% under 1 Sun (100 mW/cm2) and indoor light-emitting diode lighting (580 µW/cm2) conditions, respectively. Additionally, PEDOT:PSS is successfully slot-die-coated atop BHJ by mitigating wettability challenges with the aid of surface treatment. The all four-layer slot-die-coated OPVs exhibit a PCE of 9.55%.

RESUMEN

Upscaling large-area formamidinium (FA)-based perovskite solar cells (PSCs) has been considered as one of the most promising routes for the commercial applications of this rising photovoltaics technology. Here, a natural amino acid, phenylalanine (Phe), is introduced to regulate the nucleation and crystal growth process of the large-scale coating of FA-based perovskite films. Better film coverage and larger grain sizes are observed after adding Phe. Moreover, it is found that Phe can effectively passivate defects within perovskite films and suppress the nonradiative recombination due to the strong interaction with under-coordinated Pb2+ ions in the perovskite films. Rigid PSCs based on the blade-coated perovskite films containing Phe obtain a champion efficiency of 21.95%. The corresponding unencapsulated devices also exhibit excellent ambient stability, retaining 95% of their initial efficiencies after storage in the glovebox at 20 °C for 1000 h. Further, the strategy is applied to fabricate flexible PSCs and modules on polyethylene terephthalate/indium doped tin oxide substrates via slot-die coating. Phe modified flexible devices achieve outstanding efficiencies of 20.21%, 12.1%, and 11.2% with aperture areas of 0.10, 185, and 333 cm2 , respectively. The strategy here has paved a promising way for the large-scale production of flexible PSCs.

Asunto(s)

RESUMEN

Roll-to-roll coating of conventional organic photovoltaic architectures in air necessitates low work function, electron-harvesting interlayers as the top interface, termed cathode interlayers. Traditional materials based on metal oxides are often not compatible with coating in air and/or green solvents, require thermal annealing, and are limited in feasibility due to interactions with underlying layers. Alternatively, perylene diimide materials offer easily tunable redox properties, are amenable to air coating in green solvents, and are considered champion organic-based cathode interlayers. However, underlying mechanisms of the extraction of photogenerated electrons are less well understood. Herein, we demonstrate the utilization of two N-annulated perylene diimide materials, namely, PDIN-H and CN-PDIN-H, in air-processed conventional organic photovoltaic devices, using the now standard PM6:Y6 photoactive layer. The processing ink formulation using cesium carbonate as a processing agent to solubilize the perylene diimides in suitable green solvents (1-propanol and ethyl acetate) for uniform film formation using spin or slot-die coating on top of the photoactive layer is critical. Cesium carbonate remains in the film, creating hybrid organic/metal salt cathode interlayers. Best organic photovoltaic devices have power conversion efficiencies of 13.2% with a spin-coated interlayer and 13.1% with a slot-die-coated interlayer, superior to control devices using the classic conjugated polyelectrolyte PFN-Br as an interlayer (ca. 12.8%). The cathode interlayers were found to be semi-insulating in nature, and the device performance improvements were attributed to beneficial interfacial effects and electron tunneling through sufficiently thin layers. The efficiencies beyond 13% achieved in air-processed organic photovoltaic devices utilizing slot-die-coated cathode interlayers are among the highest reported so far, opening new opportunities for the fabrication of large-area solar cell modules.

RESUMEN

Cellulose and chitin are the two most abundant naturally produced biopolymers and are being extensively studied as candidates for renewable oxygen barrier films used in packaging. It has been shown that bilayers formed from cellulose nanocrystals (CNCs) and chitin nanofibers (ChNFs) exhibit oxygen barrier properties similar to polyethylene terephthalate (PET). However, this prior work explored only coating each layer individually in sequence through techniques such as spray coating. Here, we demonstrate the viability of dual-layer slot die coating of CNC/ChNF bilayers onto cellulose acetate (CA) substrates. The dual-layer slot die method enables significantly lower oxygen permeability versus spray coating while using a roll-to-roll system that applies the bilayer in a single pass. This work discusses suspension properties, wetting, and drying conditions required to achieve well-controlled ChNF/CNC bilayers. Spray-coated bilayer films were on average 25% thinner than the dual-layer bilayer film; however, the thickness-normalized oxygen permeability (OP) of the dual-layer-coated ChNF/CNC bilayer film on CA was 20 times better than that of the spray-coated bilayers. It has been shown that ChNF contributes to the wetting and barrier properties. Values of OP for the slot die-coated bilayers under optimized drying conditions were as low as 1.2 cm3·µm·m-2·d-1·kPa-1, corresponding to a normalized oxygen transmission rate of 0.32 cm3·m-2·d-1 at 23 °C and 50% relative humidity. It is also noted that the adhesive properties of the dual-layer coating are also improved when films are air-dried and that ChNF contributes to the wetting and barrier properties.

RESUMEN

The optimization of multicomponent emissive layer (EML) deposition by slot-die coating for organic light-emitting diodes (OLEDs) is presented. In the investigated EMLs, the yellow-green iridium complex (Ir) was doped in two types of host: a commonly used mixture of poly(N-vinylcarbazole) (PVK) with oxadiazole derivative (PBD) or PVK with thermally activated delayed fluorescence-assisted dopant (10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-10H-spiro[acridine-9,9'-fluorene], SpiroAC-TRZ). In this article, OLEDs with EML prepared in air by slot-die coating, facilitating industrial manufacturing, are confronted with those with spin-coated EML in nitrogen. OLEDs based on PVK:PBD + 2 wt.% Ir-dopant exhibit comparable performance: ~13 cd A-1, regardless of the used method. The highest current efficiency (21 cd A-1) is shown by OLEDs based on spin-coated PVK with 25 wt.% SpiroAC-TRZ and 2 wt.% Ir-dopant. It is three times higher than the efficiency of OLEDs with slot-die-coated EML in air. The performance reduction, connected with the adverse oxygen effect on the energy transfer from TADF to emitter molecules, is minimized by the rapid EML annealing in a nitrogen atmosphere. This post-treatment causes more than a doubling of the OLED efficiency, from 7 cd A-1 to over 15 cd A-1. Such an approach may be easily implemented in other printing techniques and result in a yield enhancement.

RESUMEN

Organic solar cells (OSCs) are promising candidates for next-generation photovoltaic technologies, with their power conversion efficiencies (PCEs) reaching 19%. However, the typically used spin-coating method, toxic halogenated processing solvents, and the conventional bulk-heterojunction (BHJ), which causes excessive charge recombination, hamper the commercialization and further efficiency promotion of OSCs. Here, a simple but effective dual-slot-die sequential processing (DSDS) strategy is proposed to address the above issues by achieving a continuous solution supply, avoiding the solubility limit of the nonhalogen solvents, and creating a graded-BHJ morphology. As a result, an excellent PCE of 17.07% is obtained with the device processed with o-xylene in an open-air environment with no post-treatment required, while a PCE of over 14% is preserved in a wide range of active-layer thickness. The unique film-formation mechanism is further identified during the DSDS processing, which suggests the formation of the graded-BHJ morphology by the mutual diffusion between the donor and acceptor and the subsequent progressive aggregation. The graded-BHJ structure leads to improved charge transport, inhibited charge recombination, and thus an excellent PCE. Therefore, the newly developed DSDS approach can effectively contribute to the realm of high-efficiency and eco-friendly OSCs, which can also possibly be generalized to other organic photoelectric devices.

RESUMEN

Highly flexible silver nanowire-based transparent conductive films (AgNWs TCFs) were large-scale fabricated by slot-die coating AgNWs inks on a flexible polyethylene terephthalate (PET) substrate, and further fabricated into a transparent film heater. Appropriate flow rate, coating speed, and AgNWs concentration allow the construction of the 15 cm × 15 cm AgNW TCFs with a sheet resistance (Rs) of less than 20 Ω/sq, a transmittance (T) at 550 nm higher than 95%, and a haze less than 3.5%. The resultant AgNW TCFs heater possesses high uniformity and superior mechanical stability and can reach a Joule heating temperature of 104 °C with a voltage of 12 V. The slot-die coating method has great potential for large-scale production of AgNW based film heaters promisingly used in window defrost and deicer systems.

RESUMEN

Recently, slot-die coating based on the roll-to-roll process has been actively used to fabricate nanoparticle-based electrolyte layers because it is advantageous for high-speed processes and mass production of uniformly thick electrolyte layers. In this process, the fabricated electrolyte layer is stored as a wound roll throughout the rewinding process. We analyzed the defects and geometric changes in an electrolyte layer, i.e., gadolinium-doped cerium oxide (GDC), due to the radial stress in the wound roll. We found that the thickness of the coated layer could be decreased by increasing the radial stress, i.e., cracks can be generated in the coated layer if excessively high radial stress is applied to the wound-coated layer. More thickness changes and crack defects were generated with time due to the residual stress in the wound roll. Finally, we analyzed the effects of taper tension profiles on the defects of the coated layer in the wound roll and determined the taper tension profile to minimize defects.