1:30pm - 2:00pmInvited
Harnessing Multilayer Transparent Electrodes in Optoelectronic Devices: from Ultra-efficient Flexible OLEDs to Heat-reflecting See-through Solar Cells
Korea Advanced Institute of Science and Technology, South Korea
We explore multilayer transparent electrodes (MTEs) based on triple layers consisting of an external dielectric layer, a thin conducting layer, and an interfacial transparent buffer layer as a versatile alternative to transparent conductive oxides. With systematic approaches tailored to each target application, these MTEs are shown to hold a great promise for optical enhancement of efficiency and realization of flexible/ transparent form factors in devices like organic light-emitting diodes (OLEDs) and solar cells. As a key example, this talk will introduce highly flexible and efficient OLEDs and see-through perovskite solar cells based on these MTEs. The flexible OLED adopts bottom MTEs based on TiO2 as a high-index external dielectric layer, graphene as a conducting layer, and a conducting polymer layer as a low-index internal buffer layer. The optimized high- and low-index layers in this MTE are shown to play a collaborative optical role by enhancing the cavity resonant effect yet mitigating the loss to surface plasmon polariton (SPP) excitation. Together with crack-deflection toughening mechanism of TiO2, this synergistic optical effect results in OLEDs with ultra-high external quantum efficiency that still exhibit a significant degree of mechanical flexibility . Furthermore, the non-damaging nature of MTEs is utilized as a top transparent electrode essential in semi-transparent devices with active layers having a relatively low damage threshold. With an MTE based on ZnS-Ag-MoOx, see-through perovskite solar cells with high efficiency is realized . The study further reveals that it can provide an additional benefit of thermal IR reflection, which could be useful for smart energy management.
 Jaeho Lee et al., Nature Communications 7, 11791 (2016)
 Hoyeon Kim et al., Advanced Energy Materials, 6, 1502466 (2016)
2:00pm - 2:30pmInvited
Nanocarbon for Highly Transparent and Flexible Displays
1Nagoya Institute of Technology, Japan; 2University Teknologi Malaysia, Malaysia; 3University Putra Malaysia, Malaysia; 4University Teknologi Mara, Malaysia
Transparency and flexibility are key words required for the devices of next generation. To realize the transparent and flexible devices, nanocarbon, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene, is promising. Here, nanocarbon-based highly transparent and flexible field emission displays will be dealt with. To achieve this, we are tackling several approaches using single-walled CNTs, ion-induced conical nanocarbon and carbon contained ZnO [1-3]. By combining these materials, flexible electron emitters with transparency higher than 90% was readily achievable on polymer substrates.
Crystalline structure of nanocarbon also played decisive role in the emission performance. In situ transmission electron microscopy observation revealed that the transformation from amorphous to CNT occurred during field emission process for Fe-included CNFs, thus resulting in the dramatic improvement in the emission property . For Cu-coated and Cu-included CNFs, graphene nanowire formed by the electron current flow [5, 6]. After the formation of graphene nanowire of ~ 800 nm in length and 50-100 nm in diameter, current density as high as 106 A/cm2 was achievable. This implies that the graphene formation by solid phase reaction is essential not only for the elucidation of the growth process but also for the growth area (position) control of graphene for practical device applications, such as interconnections. In the talk, low temperature graphene formation will be also demonstrated .
 P. Ghosh, et al., J. Am. Chem. Soc., 132 (2010) 4034.
 D. Ghosh, et al., Phys. Status Solidi RRL 7 (2013) 1080.
 Z. Zulkifli, et al., Phys. Status Solidi RRL 9 (2015) 145.
 M. Zamri, et al., ASC Nano, 6 (2012) 9567.
 M. S. Rosmi, et al., Scientific Reports 4 (2014) 7563.
 M. Rosmi, et al., RSC Advances 6 (2016) 82459.
 R. Vishwakarma, et al., Scientific Reports (2017) in press.
2:30pm - 3:00pmInvited
Beyond Nanowires: New Materials for Flexible Electronics
C3Nano, United States
Networks composed of billions of metallic nanowires (MNWs) are considered a strong candidate to replace indium tin oxide (ITO) as the dominant transparent electrode material. These types of materials can outperform ITO in terms of lower resistances (at a given transmission) and they exhibit far greater flexibility. However, while these networks show fairly good optical properties, their higher haze have hindered their widespread market adoption (especially in consumer and handheld electronics).
In order to overcome the shortcomings of conventional MNWs, C3Nano Inc. has developed Activegrid™ a completely new material composed of fused metallic nanowires. Fusing between adjacent nanowires occurs during the coating and drying of the Activegrid™ ink by the selective deposition of Nanoglue™- a proprietary conductive additive. By fusing the MNW into a singular metallic grid (Activegrid™), C3Nano is able to produce the highest performing transparent conductor. Activegrid™ outperforms the highest quality ITO on plastic, MNWs, and metal mesh. Furthermore, C3Nano has also developed new ways to improve the overall stability and reliability of Activegrid™. Finally, C3Nano has invented a novel way to control the color (La*b*) of solution coated transparent conductors by synthesis and utilization a special nanomaterial additive.
In this presentation, various aspects of aforementioned technology will be covered. Activegrid™’s performance vs. other transparent electrodes will be reported. The basic underlying thermodynamics and kinetics of Activegrid™ (selective deposition at NW junctions) will be described.
Finally, the supply chain, C3Nano’s business model, strategic partnerships, customer activity, and roadmap will be discussed.
3:00pm - 3:15pmOral
Transparent Resistive Switching Memory Devices from Hexagonal Boron Nitride and Graphene
Nanyang Technological University, Singapore
With the significant impact of transparent electronics and the recent advances in nanotechnology, the development of transparent circuits has attracted tremendous amount of attention and motivated various studies (e.g. emerging consumer electronics and defense applications). Transparent electronic memory would be useful in integrated transparent electronics. Resistive (switching) random access memory, in short RRAM, constitutes a promising candidate for next generation data storage devices due to its high scalability, CMOS compatibility, excellent endurance, and low power consumption. However, achieving good transparency poses limitations on the choice of materials composition, and hence, hinders the processing and device performance. Here we present a route to fabricate highly transparent RRAM using two-dimensional hexagonal boron nitride (hBN) as the active material and graphene as the electrode. Their fascinating properties (e.g. excellent optical and mechanical properties) offer an opportunity for the development of future multi-functional RRAM. The hBN-based RRAM shows excellent performance in terms of optical transmittance (~85% in the visible length), ON/OFF ratio, write/erase cycling, and retention time. These results broaden the applications of 2D nanomaterial for use as transparent RRAM which would be useful in integrated transparent circuit in future.
3:15pm - 3:30pmOral
Sustainable Synthesis of Functionalised Ink-Jet Printable Transparent Conducting Nanomaterials
1University College London (UCL), United Kingdom; 2Sun Chemical, Orpington, United Kingdom
Transparent Conducting Oxide (TCO) materials, which exhibit a combination of high transparency (>80% in the visible region) and low resistivity (10-4 Ω cm), are of interest due to their application in modern technologies such as flat panel displays, smart windows, solar cells and light emitting diodes. However, commercial TCO materials such as indium tin oxide (ITO) are problematic due to the high cost and scarcity of indium. Thus, alternative and more sustainable TCOs are required, particularly as functionalized nanoceramics, as these can be deposited under relatively mild conditions, such as by inkjet printing. Nanoparticle synthesis is largely dominated by batch production processes, often involving the use of environmentally harmful organic solvents (e.g. sol-gel or solvothermal reactions), limiting the future production of materials on an industrially relevant scale.
Continuous hydrothermal flow synthesis (CHFS) processes allow for the production of high-performance TCO nanomaterials, such as ITO or various doped zinc oxides, in a continuous process, utilizing only water as a solvent and the corresponding inexpensive metal salts. In-process reduction and/or surface functionalization of the TCO nanoparticles is also possible and gives the ability to produce highly dispersible materials suitable for formulation into ink-jet printable inks.
Our research focusses on several vital aspects in the development of industrially-relevant TCO nanomaterials, including (1) The Development of more Sustainable TCOs: Cost and sustainability issues with ITO (the industry standard) require research into alternative, earth-abundant materials offering comparable performance. We focus on the CHFS of alternative systems such as doped-ZnO with a view to the production of materials to replace ITO. (2) In-process functionalization of these nanoparticles to formulate ceramic inks: Given the high costs of most deposition methods, the ability to use controlled deposition based around inkjet printing, offers a relatively low-energy and inexpensive technique that generates thin films with excellent optical, and electrical properties.