Search results

Purpose This study aims to apply the impedance spectroscopy (IS) for analyzing the electrical behavior and extracting the equivalent circuit of single-layer flexible organic light-emitting diodes (OLEDs) with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) anode.

The preliminary ultraviolet (UV) treatment of the flexible substrate of polyethylene terephthalate (PET) influenced the conductivity of PEDOT:PSS anodes.

The IS showed that the OLED with UV-treated PET/PEDOT:PSS anodes had lower values of the contact resistance and higher value of the interface capacitance.

The obtained data were used for modeling of flexible OLEDs with polymeric anodes and calculation of important display parameters such as pixel refresh ratio, signal delays and energy losses due to contact resistances. These parameters were compared for PEDOT:PSS anodes deposited on PET treated and non-treated by UV.

This review paper aims to introduce the inkjet printing as a tool for fabrication of flexible/wearable sensors. It summarizes inkjet printing techniques including various modes of operation, commonly used substrates and inks, commercially available inkjet printers and variables affecting the printing process. More focus is on the drop-on-demand printing mode, a strongly considered printing technique for patterning conductive lines on flexible and stretchable substrates. As inkjet-printed patterns are influenced by various variables related to its conductivity, resistivity, durability and dimensions of printed patterns, the main printing parameters (e.g. printing multilayers, inks sintering, surface treatment, cartridge specifications and printing process parameters) are reported. The embedded approaches of adding electronic components (e.g. surface-mounted and optoelectronic devices) to the stretchable circuit are also included.

In this paper, inkjet printing techniques for fabrication of flexible/stretchable circuits will be reviewed. Specifically, the various modes of operation, commonly used substrates and inks and variables affecting the printing process will be presented. Next, examples of inkjet-printed electronic devices will be demonstrated. These devices will be compared to their rigid counterpart in terms of ease of implementation and electrical behavior for wearable sensor applications. Finally, a summary of key findings and future research opportunities will be presented.

In conclusion, it is evident that the technology of inkjet printing is becoming a competitor to traditional lithography fabrication techniques, as it has the advantage of being low cost and less complex. In particular, this technique has demonstrated great capabilities in the area of flexible/stretchable electronics and sensors. Various inkjet printing methods have been presented with emphasis on their principle of operation and their commercial availability. In addition, the components of a general inkjet printing process have been discussed in details. Several factors affect the resulting printed patterns in terms of conductivity, resistivity, durability and geometry.

The paper focuses on flexible/stretchable optoelectronic devices which could be implemented in stretchable circuits. Furthermore, the importance and challenges related to printing highly conductive and highly stretchable lines, as well as reliable electronic devices, and interfacing them with external circuitry for power transmission, data acquisition and signal conditioning have been highlighted and discussed. Although several fabrication techniques have been recently developed to allow patterning conductive lines on a rubber substrate, the fabrication of fully stretchable wearable sensors remains limited which needs future research in this area for the advancement of wearable sensors.

Due to rapid technological evolution driven by display manufacturers, the television (TV) market of flat panel displays has been fast growing with the advancement of digital technologies in broadcasting service. Recently, organic light-emitting diode (OLED) successfully penetrated into the large-size TV market, catching up with light-emitting diode (LED)-liquid-crystal display (LCD). This paper aims to investigate the market penetration of OLED technologies by determining their technology adoption rates based on a diffusion model.

Through the rapid evolution of information and communication technology, as well as a flood of data from diverse sources such as research awards, journals, patents, business press, newspaper and Internet social media, data mining, text mining, tech mining and database tomography have become practical techniques for assisting the forecaster to identify early signs of technological change. The information extracted from a variety of sources can be used in a technology diffusion model, such as Fisher-Pry where emerging technologies supplant older ones. This paper uses a comparison-based prediction method to forecast the adoption and diffusion of next-generation OLED technologies by mining journal and patent databases.

In recent years, there has been a drastic reduction of patents related to LCD technologies, which suggests that next-generation OLED technology is penetrating the TV market. A strong industry adoption for OLED has been found. A high level of maturity is expected by 2026.

For OLED technologies that are closely tied to industrial applications such as electronic display devices, it may be better to use more industry-oriented data mining, such as patents, market data, trade shows, number of companies or startups, etc. The Fisher-Pry model does not address the level of sales for each technology. Therefore, the comparison between the Bass model and the Fisher-Pry model would be useful to investigate the market trends of OLED TVs further. Another step for forecasting could include using industry experts and a Delphi model for forecasting (and further validation).

Fisher-Pry growth curves for journal publications and patents follow the expected sequence. Specially, journal publications and patents growth curves are close for OLED technologies, indicating a strong industry adoption.

The paper aims to explore two developing display technologies, organic light emitting diodes (OLEDs) and e‐paper, with a view to assessing their potential to disrupt existing markets and thereby offer an opportunity for European firms to play a larger role in the Information and communication technologies (ICTs) sector.

The paper is based on an extensive study including literature review and detailed desk research on the technologies themselves, their potential application and market analysis. Selected interviews with industry representatives were also carried out, which further informed a detailed value chain analysis and assessment of the EU position in these technologies.

OLEDs and e‐paper have the potential to disrupt current displays market and in so doing they may enable EU companies to enter at selected points in the value chain to compete with the Asian ICT industry.

Although there is a huge literature on the technical aspects of these technologies, speculative market analysis and journalistic assessments, this paper brings all of these facets together in a sophisticated value chain analysis that indicates opportunities for Europe's ICT sector.

The paper's aim is to present a method for integrating high‐performance circuit components onto flexible substrates using self‐assembly. The basic process of self‐assembly at the micrometer‐scale is reviewed and recent work in building functional parts such as silicon transistors and compound semiconductor light emitting diodes, as well as their integration onto flexible plastic templates, is reported.

A micron‐scale self‐assembly method was used for building flexible circuits. In micron‐scale self‐assembly, functional micro‐components are independently microfabricated and subsequently allowed to self‐assemble on a template with electrical interconnects and corresponding binding sites in a fluid.

The self‐assembly process can achieve heterogeneous integration with a potentially very high yield. Successful assembly of functional micro‐components such as LEDs and transistors on plastic has been demonstrated.

The paper demonstrates fabrication techniques for free‐standing micro‐components with novel designs, low‐temperature fabrication on thin plastic sheets, and using capillary‐gravity‐based self‐assembly for the integration of crystalline inorganic semiconductor components onto unconventional substrates such as flexible polymers.

This study aims to propose a hybrid technology evaluation process integrating the Decision Making Trial and Evaluation Laboratory (DEMATEL) technique and the analytic network process (ANP) with novel MCDM method for the organic light emitting diode (OLED) technology evaluation. The DEMATEL is used to detect and build the complex network relationship map (NRM) among dimensions/criteria. The ANP is employed to conduct the dependence and feedback among criteria and to decide the relative weights of the criteria by super‐matrix. The combination of DEMATEL technique and ANP with novel MCDM method is used to perform for constructing a technology evaluation structure.

This study proposes a hybrid approach integrating the DEMATEL and the ANP to construct a technology evaluation and decision‐making model for OLED. Taiwan is a research base in this study. This is for the purpose of offering an example as to how a technology firm or even a country can evaluate or position certain emerging technology in the process of resource investment decision‐making.

This study suggests a hybrid technology evaluation approach integrating the DEMATEL technique and the ANP approach. When policy makers and R&D planners design R&D programs in emerging technology fields, the authors' proposed model can help to assess whether it is worth investing in the expected technology or not, for all concerned. Besides, using Taiwan's OLED as an example, this study has generated a conclusion comprising several strategic suggestions and managerial implications.

The whole approach developed by this study can serve as a reference to construct an evaluation framework to evaluate other technology fields in order to propose some guidance for R&D planning or strategy making in the industry applied the aimed technology. The weights distributed to the prospects and the problems can also serve as a reference of whether the R&D investment in the new technology is worthwhile for all concerned. Future research can adopt the approach proposed in this study to evaluate the worth of R&D investment in other targeted technologies.

The purpose of this paper is to study the effect of on device performance by selectively annealing ITO substrates and TPD:PVK layers of the OLED at different temperatures with a certain annealing time.

Thermal annealing was carried out on the ITO anode at different temperatures (150, 350, 500°C) with a constant time (100 min); but also before the deposition of the tris(8‐hydroxyquinolato) aluminum (Alq₃) layer, at the same time, thermal treatment was carried out on the hole transporting layers (TPD:PVK layers) at different temperatures (70, 90, 110°C), and the annealing time was 30 min. We fabricated a novel device with the structure of Al/LiF/Alq₃/TPD:PVK/NiO/ITO/Glass, and tested the sheet resistance, SEM and XRD of ITO anode after annealing, at the same we also tested the I‐V, L‐V and current efficiency characteristics of OLED.

When the TPD:PVK layers were annealed at 90°C with 30 min annealing time and ITO substrates were annealed at 350°C with a constant annealing time (100 min), we find that the OLED shows obvious performance improvement, which is attributable to the fact that annealing reduces defects and improves the interface structures of organics and organic/ITO interface. On the other hand, an annealing TPD:PVK layers would slow and even impede the transport of holes, and finally leads to more balanced electron and hole injection processes.

The paper shows that the annealing method can be used to prepare high‐performance organic light‐emitting device.

The purpose of this paper is to present a comparative study between two low‐cost turbidimeter designs using a multi purpose Optical Fiber NIR System (OF‐NIRS), Optical Fiber NIR System‐Modified (OF‐NIRS‐M) and High Sensitivity NIR System (HS‐NIRS) conducted in the development of a turbidimeter by closely replicating the existing standard design guideline. Optical method is a typical measuring technique that has been applied intensively for the measurement of water turbidity.

Comprehensive guidelines for the development of turbidimeter have been stated by the United States Environmental Protection Agency (EPA Method 180.1) and the International Organization for Standardization (ISO 7027) and have been used as standards by instrument's manufacturers world wide, including the designs presented in this work. The development commonly does not only establish through physical instrumentation aspects, but also emphasizes on the physics of light‐matter interaction such as scattering and absorption that is embedded within the science of turbidity. The individual system design is the assembly of light emitting diode (LED) and photo detector with near infrared (NIR) band, amplifier, 12‐bit analogue to digital converter (ADC) and Basic Stamp 2pe microcontroller.

The measurement by OF‐NIRS produces coefficient of determination, R2=0.8881 with standard error of 20.33 NTU while HS‐NIRS produces higher precision result with R2=0.995 with standard error of 1.809 NTU. A modified version of OF‐NIRS (OF‐NIRS‐M) has been introduced and consists of direct emission of NIR radiation to the sample. OF‐NIRS‐M produces R2=0.9921 with standard error of 2.37 NTU, a high linearity result, comparable to HS‐NIRS.

This research introduced a fundamental design of a turbidimeter by following closely to the existing standards at much lower cost. This work presents a comparative study between two main designs that utilize different types of photo detector and amplification circuitry and enables related industry to develop their own in‐house turbidity monitoring system with flexible sensitivity.