Fabricating Silver Nanowire–IZO Composite Transparent Conducting Electrodes at Roll-to-Roll Speed for Perovskite Solar Cells

Article “Green” Fabrication of High-performance Transparent Conducting Electrodes by Blade Coating and Photonic Curing on PET for Perovskite Solar Cells Justin C. Bonner 1,†, Robert T. Piper 1,†, Bishal Bhandari 2, Cody R. Allen 2, Cynthia T. Bowers 3,4, Melinda A. Ostendorf 3,4, Matthew Davis 5, Marisol Valdez 6, Mark Lee 2 and Julia W. P. Hsu 1,∗ 1 Department of Materials Science and Engineering, University of Texas at Dallas, 800 W Campbell Road, RL-10, Richardson, TX 75080, USA 2 Department of Physics, University of Texas at Dallas, 800 W Campbell Road, Richardson, TX 75080, USA 3 Materials Characterization Facility at the Air Force Research Laboratory, 2941 Hobson Way, WPAFB, OH 45433, USA 4 UES, Inc., a BlueHalo Company, 4401 Dayton-Xenia Rd, Dayton, OH 45432, USA 5 Energy Materials Corporation, 1999 Lake Ave B82 Ste B304, Rochester, NY 14650, USA 6 Department of Chemistry, University of Texas at Dallas, 800 W Campbell Road, Richardson, TX 75080, USA * Correspondence: jwhsu@utdallas.edu † These authors contributed equally to this work. Received: 30 September 2024; Revised: 25 October 2024; Accepted: 30 October 2024; Published: 5 November 2024 Abstract: This study presents an innovative material processing approach to fabricate transparent conducting electrodes (TCEs) on polyethylene terephthalate (PET) substrates using blade coating and photonic curing. The hybrid TCEs consist of a multiscale Ag network, combining silver metal bus lines and nanowires, overcoated by an indium zinc oxide layer, and then photonically cured. Blade coating ensures film uniformity and thickness control over large areas. Photonic curing, a non-thermal processing method with significantly lower carbon emissions, enhances the conductivity and transparency of the coated layers. Our hybrid TCEs achieve an average transmittance of (81 ± 0.4)% referenced to air ((90 ± 0.4)% referenced to the PET substrate) in the visible range, an average sheet resistance of (11 ± 0.5) Ω sq−1, and an average surface roughness of (4.3 ± 0.4) nm. We benchmark these values against commercial PET/TCE substrates. Mechanical durability tests demonstrate <3% change in resistance after 2000 bending cycles at a 1 in radius. The scalable potential of the hybrid TCE fabrication method is demonstrated by high uniformity and excellent properties in 7 in × 8 in large-area samples and by performing the photonic curing process at 11 m min−1. Furthermore, halide perovskite solar cells fabricated on these hybrid TCEs achieve average and champion power conversion efficiencies of (10.5 ± 1.0) % and 12.2%, respectively, and significantly outperform devices made on commercial PET/TCEs. This work showcases our approach as a viable pathway for high-speed “green” manufacturing of high-performance TCEs on PET substrates for flexible optoelectronic devices.

Flexible transparent conducting electrodes (TCEs) are critically important for next-generation optoelectronics, attracting significant interest across diverse research fields. This study presents a clear and timely advance in their manufacturing by demonstrating a scalable, hybrid TCE. The authors combine blade-coated silver nanowires (AgNWs) with flexographically printed metal bus lines (MBLs), cap the structure with an indium zinc oxide (IZO) overcoat, and subsequently fuse the stack using intense pulsed light (IPL) photonic curing. This approach yields a multiscale conductor on polyethylene terephthalate (PET) substrates that simultaneously achieves low sheet resistance, high transparency across the visible and near-infrared spectrum, and low surface roughness. The work is explicitly framed around “green” manufacturing principles, emphasizing a low thermal budget, inherent compatibility with roll-to-roll (R2R) processing, and impressive line speeds of up to 11 m·min−1 in stitching mode. Moving beyond fundamental materials metrics, the authors underscore the device-level relevance of their TCE by fabricating p-i-n perovskite solar cells (PSCs). These devices achieved champion power conversion efficiencies (PCEs) of up to 12.2% (averaging ~10.5%), outperforming commercial PET/ITO-based controls by approximately 50%. In this commentary, we first recognize the study’s substantive contributions to scalable TCE fabrication. We then propose practical refinements that could further strengthen the scientific rigor and translational potential of the technology. Finally, we conclude with a constructive critique of several unresolved questions; addressing these would undoubtedly represent a significant advance for the field.

Patterned flexible Silver Nanowire/2D MXene transparent conducting electrode for organic light-emitting diodes

The flexible and highly stable graphene oxide (GO)/silver nanowires (AgNWs) hybrid transparent conductive electrode (TCE) was fabricated by coating AgNWs and GO inks on the surface of polyethylene terephthalate (PET) using a Meyer rod. The as-prepared GO/AgNWs hybrid TCE with a GO concentration of 0.75 mg·ml−1 exhibits excellent optoelectronic performances with a sheet resistance of 25 Ω·sq−1, a transmittance of 87.6% at 550 nm, and a lower surface roughness with a root mean square (RMS) roughness value of 4.86 nm. The existence of protective GO layer endows excellent thermal oxidation resistance and outperforming mechanical stabilities for GO/AgNWs hybrid TCE even at the conditions of temperature 80 °C, relative humidity (RH) 75% for 16 days, at room temperature in ambient air for 3 months, and mechanical bending of 2200 times, respectively. The GO/AgNWs hybrid TCE is a promising candidate for ITO used in optical devices such as organic light-emitting diodes (OLEDs), solar cells and flat panel displays.

Silver nanowires (AgNWs) and new-type two-dimensional material MXene have shown great prospects for applications in new-generation flexible electronic devices due to their brilliant properties. In this work, high-performance silver nanowire/MXene hybrid transparent conductive electrodes (TCEs) were prepared by a solution method. It studied the influence of AgNW concentration on the photoelectric properties of TCEs. Then, several-layer or even single-layer MXene were obtained by a delamination process and were added to the AgNW networks to prepared flexible hybrid electrodes on polyethylene naphtholate (PEN) substrates. The hybrid TCEs showed a low sheet resistance of 24.4 Ω/sq with the transmittance of 90.6% at 550nm. Moreover, the MXene sheets covered on the surface could improve the conductivity of the film and block the oxidation of silver nanowires. The results mean that the novel AgNW/MXene TCEs have great potential for the practical applications of high-performance flexible electronic devices.

A hydrothermal method for synthesizing ultralong and thin copper nanowires (CuNWs) with average diameter of 35 nm and average length of 100 μm is demonstrated in this paper. The concerning raw materials include copric (II) chloride dihydrate (CuCl2·2H2O), octadecylamine (ODA), and ascorbic acid, which are all very cheap and nontoxic. The effect of different reaction time and different molar ratios to the reaction products were researched. The CuNWs prepared by the hydrothermal method were applied to fabricate CuNW transparent conductive electrode (TCE), which exhibited excellent conductivity-transmittance performance with low sheet resistance of 26.23 Omega /square and high transparency at 550 nm of 89.06% (excluding Polyethylene terephthalate (PET) substrate). The electrode fabrication process was carried out at room temperature, and there was no need for post-treatment. In order to decrease roughness and protect CuNW TCEs against being oxidized, we fabricated CuNW/poly(methyl methacrylate) (PMMA) hybrid TCEs (HTCEs) using PMMA solution. The CuNW/PMMA HTCEs exhibited low surface roughness and chemical stability as compared with CuNW TCEs.

In this paper, hybrid transparent conductive electrodes (TCEs) consisting of oblique-angle deposited indium tin oxide (OAD ITO) and silver nanowires (Ag NWs) were developed forGaN-based light-emitting diodes (LEDs). The 100-nm thick OAD ITO acted as an Ohmic contact to p-GaN with negligible light absorption having optical transmittance as high as approximately 99% at 450 nm, and Ag NWs acted as a favorable current spreader with sheet resistance as low as $19.9~\Omega $ /sq. Consequently, the hybrid TCEs consisting of OAD ITO and Ag NWs yielded an optical transmittance of 93% at 450 nm, a sheet resistance of 18.9 $\Omega $ /sq, and a specific contact resistance of ${2.1} \times {10}^{-2} \Omega \cdot $ cm2. LEDs fabricated with hybrid TCEs demonstrated improved electrical properties and greater optical output powers than the reference LEDs. This was due to the combined effects of the improved optical transparency, the enhanced current spreading, and the surface roughening effect.

We present highly flexible Ag nanowire (AgNW) networks welded with transparent conductive oxide (TCO) for use in electrical interconnects in flexible and wearable electronic devices. The hybrid transparent conductive electrodes (TCEs) produced on polymer substrates consist of AgNW networks and TCO that is deposited atop the AgNWs. The TCO firmly welds the AgNWs together at the junctions and the AgNWs to the polymer substrates. Transmission electron microscopy (TEM) analysis show that TCO atop and near AgNWs grows as crystalline because AgNWs act as crystalline seeds, but the crystallinity of the matrix TCO can be controlled by sputtering conditions. The sheet resistances (Rs) of hybrid TCEs are less than the AgNW networks because junction resistance is significantly reduced due to welding by TCO. The effect of welding on decreasing Rs is enhanced with increasing matrix crystallinity, as the adhesion between AgNWs and TCO is improved. Furthermore, the bending stability of the hybrid TCEs are almost equivalent to and better than AgNW networks in static and cyclic bending tests, respectively. Flexible organic light-emitting diodes (f-OLEDs) are successfully fabricated on the hybrid TCEs without top-coats and the performances of f-OLEDs on hybrid TCEs are almost equivalent to those on commercial TCO, which supports replacing indium tin oxide (ITO) with the hybrid TCEs in flexible electronics applications.

High aspect ratio copper nanowires were synthesized, using a solution-based approach. The nanowires along with reduced graphene oxide thin films were sprayed onto glass and flexible substrates and later annealed in order to produce transparent conducting electrodes (TCEs). These electrodes exhibited 91.5% optical transmissivity and around 9- Ω/sq sheet resistance, which are comparable to Indium Tin Oxide (ITO). In addition, the hybrid TCEs, when exposed to ambient temperature showed slowed sheet resistance degradation. The electrodes deposited on a flexible substrate, showed immunity against any notable changes in the sheet resistance, when gone through numerous bending cycles. Adaption of such nanomaterials in conducting films could lead to the potential alternatives for the conventional ITO, with applications in numerous industries, including solar cells manufacturing.

Transparent conductive electrodes (TCE) were fabricated by combining three emerging nano-materials: copper nanowires (CuNWs), zinc oxide (ZnO) nano-particulate thin films, and reduced graphene oxide (rGO) platelets. Whereas CuNWs are responsible for essentially all of the electrical conductivity of our thin-film TCEs, the ZnO matrix embeds and strengthens the CuNW network in its adhesion to the substrate, while the rGO platelets provide a protective overcoat for the composite electrode, thereby improving its stability in hot and humid environments. Our CuNW/ZnO/rGO hybrid electrodes deposited on glass substrates have low sheet resistance (Rs ∼ 20 Ω/sq) and fairly high optical transmittance (T550 ∼ 79%). In addition, our hybrid TCEs are mechanically strong and able to withstand multiple scotch-tape peel tests. Finally, these TCEs can be fabricated on rigid glass as well as flexible plastic substrates.

We investigated various properties of AgNW‐transparent conductive oxide (TCO)‐conducting polymer (CP) hybrid electrodes for the application in flexible organic light emitting diodes (OLEDs). The hybrid transparent conductive electrodes (TCEs) fabricated on plastic substrates consists of AgNW networks, Indium zinc oxide (TCO) and CP that is deposited on top of the AgNW.

In solar cell research, transparent conducting electrodes (TCEs) are typically not included in device optimization. In this study, we investigate the properties of TCEs to identify the most important one(s) for the performance of large-area perovskite solar cells (PSCs), which is vital for advancing their commercial viability. By keeping the absorber and the PSC device structure constant, we pinpoint the TCE conductivity as the critical factor. We then design a hybrid TCE, composed of silver nanowires (AgNWs) and indium zinc oxide layers on a polyethylene terephthalate substrate, which has a sheet resistance ( R □ ) lower by a factor of 2 (∼5.7 vs. 9.8 Ω □ −1 ), with only a minor trade-off in average transmittance and surface roughness. PSCs with a 1.4 cm 2 device size fabricated on the lower- R □ hybrid TCE have enhanced PSC performance due to improved fill factor (FF). Furthermore, we show that the FF and power conversion efficiency of the 1.4 cm 2 area PSCs decrease with increasing series resistance, which is not observed for the 0.1 cm 2 area PSCs. Finally, technology computer-aided design simulations further confirm the experimental results and indicate that the TCE R □ must be below 10 Ω □ −1 to achieve good performance in large-area devices. These findings highlight the importance of TCE design for specific applications and that AgNW-based TCEs offer an effective pathway to improving the performance of large-area PSCs.

Transparent conductive electrodes (TCEs) based on hybrid structures (silver nanowires) have been compressively reconnoitered in next-generation electronics such as flexible displays, artificial skins, smart windows, and sensors because of their admirable conductivity as well as flexibility, which make them favorable substitutes to replace ITO (indium tin oxide) as a transparent conductor. Nevertheless, silver-based TCEs grieve from poor stability because of the corrosion and oxidation of silver in electrolytes. To overcome these issues, a RGO (reduced graphene oxide) layer on silver was promoted to resolve the difficulties of corrosion and oxidation in the electrolyte. Moreover, we successfully designed and demonstrated low-voltage WO3-based electrochromic devices (ECDs) with fabricated hybrid TCEs. The hybrid electrodes with RGO/silver nanowires/metal grid/PET (RAM) electrode exhibited improvements in the switching stability and optoelectronic properties, such as the sheet resistance (0.714 ohm/sq) as well as optical transparency of 90.9%. The coloration and bleaching behavior of the ECD was observed in an applied low-voltage range of -1.0 to 0.0 V with a maximum optical difference of 72% at 700 nm, which yielded a coloration efficiency (η) of ∼33.4 cm2/C. The highly conductive hybrid TCEs exhibit favorable features for numerous embryonic flexible electronics and optoelectronic devices.

Flexible, free-standing transparent conducting electrodes (TCEs) with simultaneously tunable transmittances up to 98% and sheet resistances down to 11 Ω/sq were prepared by a facile spray-coating method of silver nanowires (AgNWs) onto dry-spun multiwall carbon nanotube (MWNT) aerogels. Counterintuitively, the transmittance of the hybrid electrodes can be increased as the mass density of AgNWs within the MWNT aerogels increases; however, the final achievable transmittance depends on the initial transparency of the MWNT aerogels. Simultaneously, a strong decrease in sheet resistance is obtained when AgNWs form a percolated network along the MWNT aerogel. Additionally, anisotropic reduction in sheet resistance and polarized transmittance of AgNW/MWNT aerogels is achieved with this method. The final AgNW/MWNT hybrid TCEs transmittance and sheet resistance can be fine-tuned by spray-coating mechanisms or by choosing initial MWNT aerogel density. Thus, a wide range of AgNW/MWNT hybrid TCEs with optimized optoelectronic properties can be achieved depending of the requirements needed. Finally, the free-standing AgNW/MWNT hybrid TCEs can be laminated onto a wide range of substrates without the need of a bonding aid.

Flexible PEDOT: PSS/ITO hybrid transparent conducting electrode for organic photovoltaics