Quantum Dot downconverters can provide a scalable solution to tri‐color high‐resolution microLED and OLED displays by converting monochrome displays using photopatternable red and green QDs. Using internal measurements collected at NanoPattern Technologies, Inc. we model and discuss the practical wall plug efficiencies for downconverted InGaN blue microLED displays. In the range of 5 μm pixel sizes, using uncorrected 65 % film PLQY, the downconverted InGaN red emitter achieves a comparable external quantum efficiency compared to a direct red emitting AlInGaP when compared at practical current densities for microLED drivers.

Quantum Dot downconverters will enable high‐resolution, bright, and wide color gamut displays for all display formats. We have developed a method to directly photopattern densely packed InP/ZnS Quantum Dots that achieve an optical density of 2 at sub 10 µm thicknesses while preserving high photoluminescence quantum yield.

We report on white LEDs for the general illumination market with red colloidal quantum dots (QDs) applied in an on‐chip configuration. Red QDs, in combination with conventional phosphors, lead to LED conversion efficiency improvements that close the gap between 80 and 90 color rendering indexes (CRI) down to within 6% efficacy on a normalized Lm/W basis. We report on QDs colorcloud distribution compared to commercial phosphors in a large scale LED production and on a 7% performance gain from QDs in a chip on board (COB) LED device architecture.

The total available market size for high color gamut in display applications including TVs, smart phones, and tablets is rapidly growing and expected to exceed $1 billion by 2020. It is highly desirable to use quantum dots (QD), with narrow emission line widths, and narrow band red phosphors (e.g., SLA) materials to achieve high color gamut. An on-chip converter application is preferred over remote configurations because this provides lower cost and lower complexity for LED use in all sizes of displays. We discuss development of on-chip QD LEDs and narrow band phosphor LED solutions for display applications.

We demonstrate the first commercial production–ready white light-emitting diodes (LEDs) for the general illumination market with red colloidal quantum dots (QDs) applied in an on–chip configuration. We show the red QDs with tunable peak emission and narrow full width at half-maximum in combination with a conventional phosphor material can lead to LED conversion efficiency improvements of 5% to 15% over commercial phosphor based LEDs at correlated color temperatures (CCTs) ranging from 5000 to 2700 K. Furthermore, the challenges associated with reliability under high temperature, high blue flux intensity, and high humidity operation have been overcome to meet consumer market requirements. Finally, a demonstrator lamp at 3000 K color temperature and 90 color rendering index (CRI) with QD based LEDs show a larger efficiency gain up to 17%, attributed to the reduced blue LED droop from the lower drive current and the lower heat sink temperature when compared to a standard phosphor based LED lamp output.

Droop, the decrease of efficiency with increased power density, became a major topic with InGaN LEDs, after its introduction in 2007. This paper provides insight into droop in localized center luminescence phosphors, exemplified here by Eu2+ doped materials. This topic is of increasing importance, as high brightness blue LEDs have reached outputs >1 W/mm(2). The nonlinearities in phosphor quantum efficiency result in drive-dependent color point shift and reduc-tion of overall efficiency of phosphor converted white LEDs which utilize Eu2+ activated phosphors. The efficiency quenching can be traced back to two processes, well-known in laser physics, excited state absorption or/and cross relaxation by Foerster/Dexter transfer. Both processes lead to reduction in phosphor efficiency, but they can be differentiated. Understanding the root cause of efficiency quenching opens ways to minimize the practical consequences. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Injection of point defects into GaAs/Al x Ga 1-x As heterostructures by oxidation of Al x Ga 1-x As is investigated. The blueshift of the PL emission from GaAs quantum wells is measured as a function of rapid thermal annealing conditions in as-grown and thermally oxidized samples. Contrary to published data for point defect injection by oxidation of GaAs, oxidation of Al x Ga 1-x As appears to reduce the interdiffusion of the quantum wells. The PL peak shifts after annealing have been fit assuming Al diffusion in the quantum wells and solving the singleparticle Schrödinger equation. These fits show a reduction in group-III diffusivity of over an order of magnitude with an oxidized layer of Al x Ga 1-x As on the surface.

Using solution micelles formed by a block copolymer template, a variety of highly ordered catalytically active transition metal nanoparticles, ranging from single metallic nanoparticles of Fe, Co, Ni and Au to bimetallic nanoparticles such as Ni/Fe with uniform size and periodicity, have been created. These nanoparticles are excellent catalyst systems for the synthesis of carbon nanotubes and silicon nanowires. High quality, small diameter carbon nanotubes and silicon nanowires with narrow size distribution have been successfully produced. Since this block copolymer is fully compatible with conventional top-down photolithography, spatially selective growth of carbon nanotubes and silicon nanowires on a surface or carbon nanotubes suspended across trenches have been achieved using standard semiconductor processing techniques. The ability of the block copolymer template to generate catalyst with adjustable size and composition on a variety of surfaces not only enhance the manufacturability of these 1D nanobuilding blocks but also facilitates studying the growth mechanism.

Fully phosphor-converted LEDs (FpcLeds) with saturated emission have been realized in the green and amber spectral region. With the Lumiramic(TM) phosphor technology it is possible to achieve high package efficiency with minimum transmission of blue light from the primary LED source. This is done by keeping the scattering properties of the phosphor layer low while the phosphor thickness is chosen to fully convert all blue LED emission. It is shown that this can be done not only for optically isotropic Lumiramic materials like garnets, but also for oxonitridosilicate materials like the green emitting Europium doped SrSi2O2N2, crystallizing in a triclinic lattice with three optical axes. The scattering power of the Lumiramic can be decreased to acceptable levels by increasing the size of the crystallites in the densely sintered ceramics. Light propagation is found to be described well with Mie scattering of mono-sized SrSi2O2N2 spheres with refraction index differing by 0.07 to the refractive index of a SrSi2O2N2 matrix material. Using this technology, the green-yellow gap of visible light emitting LEDs can be bridged and color tunable lamps with the efficiency and flux of today's white phosphor-converted LEDs become feasible.

Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and an uncooled, 160×120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and 10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong contrast between metallic materials and those of plastic, cloth, and paper - supporting the viability of this imaging technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.

Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160 x 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.