Search

We report an ultra-bright, highly efficient, low roll-off, inverted quantum dot-based red light emitting device (QLED) using solution-processed zinc oxide nanoparticles and cesium carbonate films as the electron injection and hole blocking layers, respectively. Record luminance of 165,000 Cd/m2 has been obtained at a current density of 1000 mA/cm2 with a low driving voltage of 5.8 V for deep red device with CIE coordinates of (0.69, 0.31).

The mainstream commercialization of colloidal quantum dots (QDs) for light-emitting applications has begun: Sony televisions emitting QD-enhanced colors are now on sale. The bright and uniquely size-tunable colors of solution-processable semiconducting QDs highlight the potential of electroluminescent QD light-emitting devices (QLEDs) for use in energy-efficient, high-color-quality thin-film display and solid-state lighting applications. Indeed, this year’s report of record-efficiency electrically driven QLEDs rivaling the most efficient molecular organic LEDs, together with the emergence of full-color QLED displays, foreshadow QD technologies that will transcend the optically excited QD-enhanced products already available. In this article, we discuss the key advantages of using QDs as luminophores in LEDs and outline the 19-year evolution of four types of QLEDs that have seen efficiencies rise from less than 0.01% to 18%. With an emphasis on the latest advances, we identify the key scientific and technological challenges facing the commercialization of QLEDs. A quantitative analysis, based on published small-scale synthetic procedures, allows us to estimate the material costs of QDs typical in light-emitting applications when produced in large quantities and to assess their commercial viability.

Red quantum-dot light-emitting diodes with an external quantum efficiency of 18%, close to the theoretical maximum of 20%, are reported. Using a layer of zinc oxide nanocrystals provides highly effective electron transport, resulting in devices with a low operating voltage and a high luminous power efficiency of 25 lm W−1.

Quantum dot light emitting diodes QLEDs are a printable thin film electroluminescent technology that can deliver exceptional color and efficiency at low cost of manufacture for display and solid-state lighting applications. However, while most literature reports focus on the performance of individual test pixels, examples of working display prototypes have been sorely lacking. We report on our progress developing QLEDs for near-to-eye and direct view display applications. Both a 4″ diagonal active-matrix bottom-emitting monochrome QLED display and an 800×600 SVGA top-emitting monochrome QLED microdisplay are reported on and their performance summarized. Contract printing of high-resolution RGB QDs is also demonstrated as a milestone towards full-color displays.

LED displays utilizing quantum dots (QDs) as emitters offer several key advantages over traditional OLEDs, combining the solution processability of polymers with the high efficiency potential of phosphors, all with the stability benefits of an inorganic emitter. While QD-LEDs are at an early stage in their development, the effort toward commercialization has already led to the identification of several considerations particular to QD-LEDs. This paper explores material and design considerations for QD-LEDs and reports our progress in developing QD-LEDs for information display and advanced applications.

Microencapsulated electrophoretic (MEP) materials exhibit high optical reflectance and contrast, wide viewing angle, high resolution, and excellent image stability. MEP materials can be easily printed on large plastic sheets and laminated to a variety of electronic backplanes to construct displays. The combination of a MEP material with flexible transistor technologies enables displays that offer both the look and form of the printed page. This article reviews the basic architecture and properties of MEP materials and describes the integration of MEP materials with transistor backplanes to produce high-resolution, low-power, paperlike displays. Recent developments in ultrathin flexible displays are also reported.

With DOE Award No. DE-EE00000628, QD Vision developed and demonstrated a cost-competitive solution for increasing the light extraction efficiency of OLEDs with efficient and stable color rendering index (CRI) for solid state lighting (SSL). Solution processable quantum dot (QD) films were integrated into OLED ITO-glass substrates to generate tunable white emission from blue emitting OLED) devices as well as outcouple light from the ITO film. This QD light-enhancement substrate (QD-LED) technology demonstrated a 60% increase in OLED forward light out-coupling, a value which increases to 76% when considering total increase in multi-directional light output. The objective for the first year was an 80% increase in light output. This project seeks to develop and demonstrate a cost-competitive solution for realizing increased extraction efficiency organic light emitting devices (OLEDs) with efficient and stable color rendering index (CRI) for SSL. Solution processible quantum dot (QD) films will be utilized to generate tunable white emission from blue emitting phosphorescent OLED (Ph-OLED) devices.

Helicobacter pylori infects the mucus layer of the human stomach and causes peptic ulcers and adenocarcinoma. We have previously shown that H. pylori accumulates photoactive porphyrins making the organism susceptible to inactivation by light, and that small spot endoscopic illumination with violet light reduced bacterial load in human stomachs. This study assessed the feasibility and safety of whole-stomach intra-gastric violet phototherapy for the treatment of H. pylori infection.A controlled, prospective pilot trial was conducted using a novel light source consisting of laser diodes and diffusing fibers to deliver 408-nm illumination at escalating total fluences to the whole stomach. Eighteen adults (10 female) with H. pylori infection were treated at three U.S. academic endoscopy centers. Quantitative bacterial counts were obtained from biopsies taken from the antrum, body, and fundus, and serial urea breath tests.The largest reduction in bacterial load was in the antrum (97%), followed by body (95%) and fundus (86%). There was a correlation between log reduction and initial bacterial load in the antrum. There was no dose-response seen with increasing illumination times. The urea breath test results indicated that the bacteria repopulated in days following illumination.Intra-gastric violet light phototherapy is feasible and safe and may represent a novel approach to eradication of H. pylori, particularly in patients who have failed standard antibiotic treatment. This was a pilot study involving a small number of patients. Further research is needed to determine if phototherapy can be effective for eradicating H. pylori.

A novel integrated assembly process for miniature liquid-crystal-on-silicon displays using photodefinable benzocyclobutene resin is presented. Spin coating speed defines the cell gap, photolithography defines the cell perimeter and spacers, and thermocompression bonding provides the adhesion. The photodefined adhesive spacers provide thin liquid-crystal cell gap control (2.5 microm) with excellent uniformity (+/-100 nm) for glass-on-glass and glass-on-silicon assemblies. The resin is compatible with common liquid-crystal alignment films and exhibits a bonding shear strength of 22+/-3.2 MPa The assembly process flow and characterization of demonstration devices are described.

We describe two smart pixel array (SPA) applications of photopolymers: integrated liquid crystal (LC) cell assembly and micro-optics fabrication. In our experiments, we utilize benzocyclobutene (BCB) organic resins (or Cyclotene/sup TM/), a class of thermosetting polymers developed at the Dow Chemical Company for electronic thin film coating applications. The planarization properties, refractive index (n=1.56) and high optical transmission (>90%) of BCB resins lend themselves well to our applications.

Binary optical elements present a viable solution to several interconnection problems, including beam steering, shaping, splitting, and combining.

Quantum dot light emitting diodes (QLEDs) are a printable thin film electroluminescent technology that delivers exceptional color and efficiency at low cost of manufacture for display and solid- state lighting applications. We report on our progress developing efficient, stable QLEDs for full-color active-matrix displays, including recent advances in device performance, lifetime and Cadmium-free QLEDs. Current QLED devices exhibit peak luminance efficiencies exceeding 50 cd/A, luminous power efficiencies greater than 20 lm/W and operational lifetimes exceeding 300 hours at 1,000 nits. Our most recent QLED efficiency results suggest that today's QLED performance is within a factor of two of the theoretical limit.

Neural networks are investigated for real-time matched filter selection in an optical correlator system. The input to the neural network is a sample space of the optical Fourier transform and the output is a pointer to the correct matched filter. Smaller feedforward network models were ported to analog neural hardware. Simulation and hardware results are discussed. Some architecture recommendations are suggested, specifically an associative memory for filter synthesis.

We report on the fabrication of a prototypical flexible, active-matrix display incorporating a microencapsulated electrophoretic material and an active matrix backplane constructed with an organic semiconductor using all low temperature processes. This prototype has attributes desirable for an electronic paper display: flexibility, an ink-on-paper appearance, and low-power consumption.

— The performance and manufacturability of reflective displays can be enhanced by planarization, post-processing, and integrated assembly. Simplified methods for planarization and assembly of liquid-crystal-on-silicon (LCOS) microdisplays using polymeric resins are presented. Spin-cast benzocyclobutene (BCB) resin shows a six-fold reduction in step height on the surface of a typical LCOS backplane, at a cost significantly less than chemical mechanical polishing. Methods for dry-etching low-resistance contacts to the underlying circuitry and depositing high-reflectivity mirrors have been developed. In addition, photo-definable BCB resin has been utilized as both a spacer and adhesive technology in miniature-display assembly. Cell-gap thicknesses of 0.9–2.4 μm with 50–100-nm cell-gap variation and bonding shear strengths of 3200 ± 460 psi have been demonstrated, leading to wafer-scale assembly of LCOS cells. The photo-BCB spacer and adhesive technology is compatible with common liquid-crystal-alignment techniques. In this paper, the methods and results of LCOS backplane planarization, post-processing, and integrated display assembly are described.