Project description:Despite stringent power consumption requirements in many applications, over years organic light-emitting diode (OLED) displays still suffer unsatisfactory energy efficiency due to poor light extraction. Approaches have been reported for OLED light out-coupling, but they in general are not applicable for OLED displays due to difficulties in display image quality and fabrication complexity and compatibility. Thus to date, an effective and feasible light extraction technique that can boost efficiencies and yet keep image quality is still lacking and remains a great challenge. Here, a highly effective and scalable extraction-enhancing OLED display pixel structure is proposed based on embedding the OLED inside a three-dimensional reflective concave structure covered with a patterned high-index filler. It can couple as much internal emission as possible into the filler region and then redirect otherwise confined light for out-coupling. Comprehensive multi-scale optical simulation validates that ultimately high light extraction efficiency approaching ≈80% and excellent viewing characteristics are simultaneously achievable with optimized structures using highly transparent top electrodes. This scheme is scalable and wavelength insensitive, and generally applicable to all red, green, and blue pixels in high-resolution full-color displays. Results of this work are believed to shed light on the development of future generations of advanced OLED displays.
Project description:Electroluminescent devices based on organic semiconductors have attracted significant attention owing to their promising applications in flat-panel displays. The conventional display pixel consisting of side-by-side arrayed red, green and blue subpixels represents the mature technology but bears an intrinsic deficiency of a low pixel density. Constructing an individual color-tunable pixel that comprises vertically stacked subpixels is considered an advanced technology. Although color-tunable organic light-emitting diodes (OLEDs) have been fabricated using the vacuum deposition of small molecules, the solution processing of conjugated polymers would enable a much simpler and inexpensive manufacturing process. Here we present the all-solution processing of color-tunable OLEDs comprising two vertically stacked polymer emitters. A thin layer of highly conducting and transparent silver nanowires is introduced as the intermediate charge injection contact, which allows the emission spectrum and intensity of the tandem devices to be seamlessly manipulated. To demonstrate a viable application of this technology, a 4-by-4 pixelated matrix color-tunable display was fabricated.
Project description:To address current unmet needs in terms of scalability and material biocompatibility for future photocrosslinking-based additive manufacturing technologies, emergent platform designs are in inexorable demand. In particular, a shift from the present use of cell-damaging UV light sources in light-based three-dimensional (3D) bioprinting methods demands new platforms. We adopted an organic light-emitting diode (OLED) microdisplay as a digital visible light modulator to create a 3D printing platform modality that offers scalability and multi-material capability while forgoing the need for UV photocrosslinking. We formulate biocompatible inks that are visible light-crosslinkable with relatively quick photoinitiation rates. We demonstrated successful attachment and rapid growth of primary human dermal fibroblast-adult (HDF-a) cells on biological substrates fabricated using the OLED platform. This platform incites new possibilities by providing a simple-yet-effective means for low-cost, high-throughput, and multi-material 3D fabrication of functional structures made of polymers, ceramic composites, and biomaterials.
Project description:Recently, the role of clothing has evolved from merely body protection, maintaining the body temperature, and fashion, to advanced functions such as various types of information delivery, communication, and even augmented reality. With a wireless internet connection, the integration of circuits and sensors, and a portable power supply, clothes become a novel electronic device. Currently, the information display is the most intuitive interface using visualized communication methods and the simultaneous concurrent processing of inputs and outputs between a wearer and functional clothes. The important aspect in this case is to maintain the characteristic softness of the fabrics even when electronic devices are added to the flexible clothes. Silicone-based light-emitting diode (LED) jackets, shirts, and stage costumes have started to appear, but the intrinsic stiffness of inorganic semiconductors causes wearers to feel discomfort; thus, it is difficult to use such devices for everyday purposes. To address this problem, a method of fabricating a thin and flexible emitting fabric utilizing organic light-emitting diodes (OLEDs) was developed in this work. Its flexibility was evaluated, and an analysis of its mechanical bending characteristics and tests of its long-term reliability were carried out.
Project description:Atomically thin molybdenum disulfide (MoS2) has been extensively investigated in semiconductor electronics but has not been applied in a backplane circuitry of organic light-emitting diode (OLED) display. Its applicability as an active drive element is hampered by the large contact resistance at the metal/MoS2 interface, which hinders the transport of carriers at the dielectric surface, which in turn considerably deteriorates the mobility. Modified switching device architecture is proposed for efficiently exploiting the high-k dielectric Al2O3 layer, which, when integrated in an active matrix, can drive the ultrathin OLED display even in dynamic folding states. The proposed architecture exhibits 28 times increase in mobility compared to a normal back-gated thin-film transistor, and its potential as a wearable display attached to a human wrist is demonstrated.
Project description:Commercially available near-infrared (IR) imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits (ROIC) by indium bump bonding which significantly increases the fabrication costs of these image sensors. Furthermore, these typical III-V compound semiconductors are not sensitive to the visible region and thus cannot be used for multi-spectral (visible to near-IR) sensing. Here, a low cost infrared (IR) imaging camera is demonstrated with a commercially available digital single-lens reflex (DSLR) camera and an IR sensitive organic light emitting diode (IR-OLED). With an IR-OLED, IR images at a wavelength of 1.2 µm are directly converted to visible images which are then recorded in a Si-CMOS DSLR camera. This multi-spectral imaging system is capable of capturing images at wavelengths in the near-infrared as well as visible regions.
Project description:Inorganic semiconductor-based microscale light-emitting diodes (micro-LEDs) have been widely considered the key solution to next-generation, ubiquitous lighting and display systems, with their efficiency, brightness, contrast, stability, and dynamic response superior to liquid crystal or organic-based counterparts. However, the reduction of micro-LED sizes leads to the deteriorated device performance and increased difficulties in manufacturing. Here, we report a tandem device scheme based on stacked red, green, and blue (RGB) micro-LEDs, for the realization of full-color lighting and displays. Thin-film micro-LEDs (size ∼100 μm, thickness ∼5 μm) based on III-V compound semiconductors are vertically assembled via epitaxial liftoff and transfer printing. A thin-film dielectric-based optical filter serves as a wavelength-selective interface for performance enhancement. Furthermore, we prototype arrays of tandem RGB micro-LEDs and demonstrate display capabilities. These materials and device strategies provide a viable path to advanced lighting and display systems.
Project description:Single-walled carbon nanotube (SWNT) is expected to be a very promising material for flexible and transparent driver circuits for active matrix organic light emitting diode (AM OLED) displays due to its high field-effect mobility, excellent current carrying capacity, optical transparency and mechanical flexibility. Although there have been several publications about SWNT driver circuits, none of them have shown static and dynamic images with the AM OLED displays. Here we report on the first successful chemical vapor deposition (CVD)-grown SWNT network thin film transistor (TFT) driver circuits for static and dynamic AM OLED displays with 6 × 6 pixels. The high device mobility of ~45 cm(2)V(-1)s(-1) and the high channel current on/off ratio of ~10(5) of the SWNT-TFTs fully guarantee the control capability to the OLED pixels. Our results suggest that SWNT-TFTs are promising backplane building blocks for future OLED displays.
Project description:The use of postsynaptic current to drive long-lasting luminescence holds a disruptive potential for harnessing the next-generation of smart displays. Multiresponsive long afterglow emission can be achieved by integrating light-emitting polymers in electric spiked transistors trigged by distinct presynaptic signals inputs. Here, we report a highly effective electric spiked long afterglow organic light-emitting transistor (LAOLET), whose operation relies on a nanofloating gate architecture. Long afterglow emission with reconfigurable brightness and retention time is observed upon applying specific positive gate voltage spiked. Conversely, when negative gate voltage stimulus is applied, these LAOLETs function as click-on display. Interestingly, upon endowing the device with force sensing capabilities, it can operate as a long afterglow pressure sensor that emits long-lasting green light subsequently to a controlled extrusion action.
Project description:Culcioides biting midges (Diptera: Ceratopogonidae) are vectors of various veterinary pathogens. Suction light traps are one of the most widely used tools for vector surveillance. The present aim was to compare the efficiency for the collection of Culicoides species between newly developed 3D-printed ultraviolet (Mahidol University (MU) UV LED) and green light-emitting diode (Mahidol University (MU) Green LED) traps baited with CO2 and UV LED Center for Disease Control (CDC) light trap (BioQuip 2770) baited with CO2. The experiment consisted of two replicates of a 3 × 3 Latin square design in each three sampling locations (Location 1, 2, 3 and 4, 5, 6), for 12 nights between 26th July and 7th August 2020 in Thailand. Results showed that efficiency of the MU UV LED light trap was equivalent to that of the BioQuip 2770 trap for the collection of Culicoides. Meanwhile, the efficiency of the MU Green LED light trap was lower than that of both UV LED light traps. In the analysis of Culicoides species composition and sex-age grading, a similar pattern was observed among three light traps except for Culicoides actoni Smith. The newly developed 3D-printed UV LED light trap demonstrated the following advantages over the commercial light trap: cost saving to obtain multiple units, ease of customization and standardization, and increased availability by end-users. Although further assessments in different environmental conditions are needed, this 3D-printed light trap design could minimize the constrains in vector surveillance programs worldwide.