Hybrid Light-emitting Diodes Research Articles

Bacterial Hybrid Light-Emitting Diodes.

Photon down-converting filters with fluorescent proteins (FPs) are a new frontier in the quest for rare-earth-free and non-toxic color filters for white light-emitting diodes. There are, however, concerns related to the FP purification costs and lack of FP recyclability/reuse. Here, the direct use of bacteria in photon down-converting filters can be of utmost relevance, eliminating purification and allowing in situ production of new FPs. However, their high background autofluorescence/scattering and low stability in polymer coatings have traditionally hampered the application of Engineering Living Materials (ELMs) for photon manipulation. Indeed, there are no examples of ELMs in lighting systems. This work discloses the first protocol to prepare living spheroplasts with > 90% scattering reduction, high FP expression fairly keeping their photoluminescence figures-of-merit, and excellent resilience in polymer films over 1 year under ambient storage. This unlocked the preparation of the first bacteria hybrid light-emitting diodes integrating ELMs for photon conversion. These devices feature similar stabilities to those using purified FPs, while enabling a cost-effective strategy and active FP recycling by the simple recultivation of spheroplasts. Overall, this work introduces a successful case toward bacteria-polymer photon manipulation, in general, and a new living lighting concept, in particular.

Efficient and stable hybrid perovskite-organic light-emitting diodes with external quantum efficiency exceeding 40 per cent

Light-emitting diodes (LEDs) based on perovskite semiconductor materials with tunable emission wavelength in visible light range as well as narrow linewidth are potential competitors among current light-emitting display technologies, but still suffer from severe instability driven by electric field. Here, we develop a stable, efficient and high-color purity hybrid LED with a tandem structure by combining the perovskite LED and the commercial organic LED technologies to accelerate the practical application of perovskites. Perovskite LED and organic LED with close photoluminescence peak are selected to maximize photon emission without photon reabsorption and to achieve the narrowed emission spectra. By designing an efficient interconnecting layer with p-type interface doping that provides good opto-electric coupling and reduces Joule heating, the resulting green emitting hybrid LED shows a narrow linewidth of around 30 nm, a peak luminance of over 176,000 cd m−2, a maximum external quantum efficiency of over 40%, and an operational half-lifetime of over 42,000 h.

Stable and efficient rare-earth free phosphors based on an Mg(II) metal-organic framework for hybrid light-emitting diodes.

Stable and efficient green hybrid light-emitting diodes (HLEDs) were fabricated from a highly emissive Mg(II)-tetraphenyl ethylene derivative metal-organic framework embedded in a polystyrene matrix (Mg-TBC MOF@PS). The photoluminescence quantum yield (ϕ) of the material, >80%, remains constant upon polymer embedment. The resulting HLEDs featured high luminous efficiencies of >50 lm W-1 and long lifetimes of >380 h, making them among the most stable MOF-based HLEDs. The significance of this work relies on the combination of many features, such as the abundance of the metal ion, the straightforward scalability of the synthetic protocol, the great ϕ reached upon phosphor fabrication, and the state-of-the-art HLED performances.

Life cycle cost analysis of LED retrofit and luminaire replacements for four-foot T8 troffers

Lighting makes up 17% of electrical loads and the largest energy end use in commercial buildings. Linear fixtures are among the largest opportunities for energy efficiency improvement, given their long operating hours. With continued, rapid light-emitting diode (LED) development and more LED replacement products on the market, lighting replacement decisions become more complex and warrant re-examination. With a goal to inform building managers and other decision-makers with practical guidance on lighting replacement, this study is a life cycle cost (LCC) analysis that compares the cost–benefit of six replacement options (one fluorescent and five LED) for a 0.61 m by 1.22 m (2 ft by 4 ft) T8 recessed troffer based on data for 168 lighting products from an online vendor. Results show that direct wire (i.e. unballasted) LED retrofits are the least-cost option to replacing fluorescent lamps in terms of normalized LCC. Plug-and-play lamps suffer from a lock-in with ballasts, but their ease of installation can help spur LED adoption. In cases where an existing ballast is still usable, hybrid LED retrofits provide the least upfront cost option by deferring the cost of rewiring. LED luminaires can offer improved aesthetics and reliability; however, they have high upfront cost. Among them, luminaires with replaceable lamps offer lower cost than those without.

Optimization of LED-Based Solar Simulators for Cadmium Telluride and Microcrystalline Silicon Solar Cells

Solar simulators are instruments used for controllable measurements of the properties of solar cells in indoor environments. The purpose of this paper is to examine the peculiarities of the photoresponses of CdTe/CdSeTe and microcrystalline Si solar cells and to reveal the pathways to reduction of spectrum mismatch effects when using light-emitting diode (LED)-based or hybrid LED and halogen lamp-based solar simulators of an A+-class spectrum with a small number of sources. While only four different LED types are needed to achieve an A+-class spectrum under updated IEC 60904-9:2020 standard requirements, as demonstrated by our results, additional ultraviolet LEDs are necessary to reduce the spectrum mismatch. For hybrid solar simulator configurations, the combination of cool white LED arrays and halogen emitters can serve as a main light source. Optimized for both solar cell types, hybrid simulators have a lower spectral deviation and better spectrum coverage compared to LED-only simulators with the same number of distinct source types. In addition, our results predict lower spectral mismatch errors for optimized simulators when compared with conventional Xe lamp-based simulators.

Stable white light emission from a single organic molecule via intermolecular hydrogen bond to excited-state intermolecular proton transfer

It is widely recognized that hybrid (organic/inorganic) light emitting diodes (LEDs) are of concern because they use an organic material instead of rare earth phosphors, but extending their lifetime remains challenging. To construct organic luminescent material with high photoluminescence quantum yield (PLQY), a compound named 1-(4-(tert-butyl)phenyl)-2-(4′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′-biphenyl]-4-yl)-1H-phenanthro[9,10-d]imidazole (TPBI-BPI) was synthesized by connect two imidazoles units. The PLQY of TPBI-BPI is 0.97 in acetonitrile. The white light emission (WLE) of TPBI-BPI in ethyl acetate solution containing acetic acid was observed, and a solvent-type organic/inorganic hybrid white LED device based on TPBI-BPI was prepared. The luminance efficiency, external quantum efficiency, correlated color temperature, K, and Ra (color rendering index) of the solvent-type WLED are 21.71 lm/W, 12.76%, 6329, and 83.2 at 39.90 mA, respectively. The Commission Internationale de l´Eclairage coordinate of the solvent-type WLED is (0.3135, 0.3507). In addition, the lifetime (T70) of the device can reach 130 h. This is due to the excited state intermolecular proton transfer between TPBI-BPI and acetic acid in ethyl acetate solution after UV illumination. This enables TPBI-BPI to obtain WLE and makes the WLED spectrally stable due to this process's dissipation of UV energy. This work provides a strategy to extend the lifetime of a hybrid LED.

Homopolymeric Protein Phosphors: Overpassing the Stability Frontier of Deep‐Red Bio‐Hybrid Light‐Emitting Diodes

AbstractAlthough protein‐polymer phosphors are an emerging photon‐management filter concept for hybrid light‐emitting diodes, deep‐red‐emitting devices based on archetypal fluorescent proteins (FPs; mCherry) are still poorly performing with lifetimes <50 h under high photon‐flux excitation and ambient conditions. Here, the challenge is two‐fold: i) understanding the deactivation mechanism of red‐emitting FP‐polymer coatings and, in turn, ii) identifying the best polymer design for highly stable devices. This study first provides comprehensive photophysical/thermal/structural studies and device degradation (ambient/inert) analysis, revealing the presence of photo‐induced cis–trans isomerization and the effect of oxygen and water on the deactivation of mCherry in reference polymer coatings. Based on these findings, a new bio‐phosphor configuration using polyvinyl alcohol derivatives, in which crystallinity and amount of trapped water (stiffness and oxygen/moisture barriers) are easily controlled by the hydroxylation degree, is successfully achieved. Compared to the prior art, these devices significantly outperform the reference stability (>50‐fold enhancement), showing a brightness loss of <5% over the first 2000 h and a final device lifetime of 2600 h. Hence, this study describes a unique rationale toward designing polymers to stabilize FPs for lighting, overpassing stability frontiers in deep‐red hybrid light‐emitting diodes (HLEDs) going from hours to months.

Monolithic Multicolor Emissions of InGaN-Based Hybrid Light-Emitting Diodes Using CsPbBr3 Green Quantum Dots.

To address the increasing demand for multicolor light-emitting diodes (LEDs), a monolithic multicolor LED with a simple process and high reliability is desirable. In this study, organic-inorganic hybrid LEDs with violet and green wavelengths were fabricated by depositing CsPbBr3 perovskite green quantum dots (QDs) as the light-converting material on InGaN-based violet LEDs. As the injection current was increased, the total electroluminescence (EL) intensities of the hybrid LEDs increased, whereas the light-converted green emission efficiency of the CsPbBr3 QDs decreased. The maximum green-to-violet EL spectral intensity ratio of the hybrid LEDs with CsPbBr3 QDs was achieved with the injection current of <10 mA. Moreover, the EL spectral ratio of the green-to-violet emission decreased at an injection current of 100 mA. The light-conversion intensity of the CsPbBr3 QDs decreased linearly as the junction temperature of the hybrid LEDs was increased with increasing injection current, similar to the temperature-dependent photoluminescence degradation of CsPbBr3 QDs. In addition, the junction temperature of the hybrid LED was minimized by pulse injection to suppress the thermal degradation of QDs and increase the light conversion efficiency to green emission. Therefore, the overall emission spectrum color coordinates of the hybrid LEDs exhibited a red shift from violet to blue in the low-current region and a blue shift toward violet as the green emission of the QDs was decreased above 10 mA.

Multi-Color Light-Emitting Diodes

Multi-color light-emitting diodes (LEDs) with various advantages of color tunability, self-luminescence, wide viewing angles, high color contrast, low power consumption, and flexibility provide a wide range of applications including full-color display, augmented reality/virtual reality technology, and wearable healthcare systems. In this review, we introduce three main types of multi-color LEDs: the organic LED, colloidal quantum dots (CQDs) LED, and CQD–organic hybrid LED. Various strategies for realizing multi-color LEDs are discussed including red, green, and blue sub-pixel side-by-side arrangement; vertically stacked LED unit configuration; and stacked emitter layers in a single LED. Finally, according to their status and challenges, we present an outlook of multi-color devices. We hope this review can inspire researchers and make a contribution to the further improvement of multi-color LED technology.

From Blue to White: Sustainable Luminescent Metal Organic Framework for Hybrid Light‐Emitting Diodes

AbstractHybrid light‐emitting diodes based on photon down‐converting filters with metal organic frameworks (MOFs) are mainly restricted to cross‐breed materials (i.e., nonemissive MOFs host and guest emitters) due to the lack of highly photostable and luminescent MOFs (LMOFs). This work reports a sustainable and cost‐effective blue‐emitting Zn‐based MOF with the ligand 1,1,2,2‐tetrakis(4‐(pyridin‐4‐yl)phenyl)ethene (Zn‐2‐LMOF) and their host:guest hybrids with Rhodamine B emitter RhB@LMOF toward blue‐ and white‐emitting hybrid light‐emitting diodes (HLEDs). Zn‐2‐LMOF features blue emission (λem = 480 nm) with impressive photoluminescence quantum yield (ϕ) values of 50% (powder) and 70% (polystyrene coatings). Likewise, hybrid RhB@LMOF features a white emission with ϕ of 30–40% in polystyrene coatings. They lead to blue (Zn‐2‐LMOF; x/y CIE color coordinates of 0.28/0.47) and white (RhB@LMOF; x/y CIE color coordinates of 0.31/0.32) HLEDs with stabilities of 20 and 45 h at 50 mA on‐chip under ambient operation, respectively. Though this device performance is average in HLEDs, the device degradation is mainly attributed to the photoinduced oxidation of the ligand in the MOF structure that further leads to the RhB degradation; a key information for future developments in luminescent MOFs.

Elastic Fluorescent Protein-Based Down-Converting Optical Films for Flexible Display.

Protein-based material design provides great advantages to developing smart biomaterials with tunable structures and desired functions. They have been widely used in many biomedical applications including tissue engineering and drug delivery. However, protein-based materials are not yet widely used in optoelectronic materials despite their excellent optical and tunable mechanical properties. Here, we synthesized engineered fluorescent proteins (FPs) fused with elastic protein for the development of optoelectrical down-converting optical filters for flexible display materials. We synthesized sequence-specific FPs to tune blue, green, yellow, and red colors and fused them with elastic protein to tune mechanical properties. We fabricated flexible self-supporting film materials and characterized mechanical properties and down-converting optical properties. We also fabricated a hybrid light-emitting diode (LED) to down convert blue to desired green, red, and white colors. Furthermore, we constructed a flexible white LED using organic LED as a flexible substrate. Our modular synthesis approach of tunable bio-optoelectrical material approaches will be useful to design future biocompatible and flexible display materials and technologies.

ZnO/SiO2 encapsulation of perovskite nanocrystals for efficient and stable light-emitting diodes

Achieving long-term stable lead halide perovskite nanocrystals (PNCs) in light-emitting devices remains a significant challenge because of their fast degradation upon exposure to light, moisture, and oxygen. Here, we report a facile one-pot strategy to realize the growth of crystalline ZnO/SiO2 dual-layer encapsulation on CsPbBr3 PNCs. The encapsulation provides the PNCs with robust surface passivation to withstand the harsh condition in hybrid light-emitting diodes (LEDs) with an on-chip packaging structure. The PNCs/ZnO/SiO2 could preserve 100 % of their initial photoluminescence intensity after 500 h of continuous irradiation under a 9.6 W cm−2 blue laser. The fabricated green- and white-LEDs displayed constant light intensity at 80 % of their initial value with continuous driving at 10 mA for 500 h. We believe the excellent stability of the ZnO/SiO2 encapsulated PNCs could strongly promote the development and application of perovskite-based light-emitting and other optoelectronic devices.

A novel deep blue emitting material based on carbazole-phenylanthracene conjugate linked by saturated bond: Synthesis, physical properties and organic/inorganic hybrid light emitting diode application

Herein, a novel organic light-emitting material 9-(4-(anthracen-9-yl)benzyl)-9H-carbazole (AnPhylCz) was synthesized by linking carbazole to 9-phenylanthracene with methylene (saturated bond). Their thermal, photophysical properties and the application as organic/inorganic hybrid light-emitting diodes (LEDs) were investigated. The Td (decomposition temperature, 5% weight loss) for AnPhylCz was estimated to be 304 °C because the methylene linked with nitrogen-atom (C–N bond) in the molecule is easily broken by heat. The photoluminescence (PL) spectrum of AnPhylCz in each solvent mainly shows one main peak (423 nm) and one shoulder (403 nm) locating at deep blue region. The organic/inorganic hybrid LED (device GXC-B) based on AnPhylCz shows deep blue emission with Commission Internationale de l'Eclairage chromaticity coordinate of (0.1598, 0.0481) at 29.90 mA, and device GXC-B exhibits lifetime of 12.7 min due to the homolytic reaction of AnPhylCz (C–N bond) under ultraviolet. In contrast the lifetime of organic/inorganic hybrid LED is not improved by adopting the organic light-emitting material which linking the luminescent units with saturated bond.

Quantum-dot and organic hybrid light-emitting diodes employing a blue common layer for simple fabrication of full-color displays

Quantum-dot and organic hybrid light-emitting diodes employing a blue common layer for simple fabrication of full-color displays

A Hybrid LED Sink Driver Combining a Buck-Boost Converter and a Switched-Capacitor Step-Up Converter with Nested Topology

For LED lighting applications, this paper presents a novel light emitting diode (LED) sink driver with high voltage gains. Unlike traditional LED sink drivers, the proposed LED sink driver consists of a buck-boost converter and a switched-capacitor (SC) step-up converter with nested topology, where an input voltage is converted twice by cascading these two converter blocks. Therefore, the proposed hybrid topology enables the LED sink driver to achieve not only flexible control of an output voltage but also high voltage gains and few passive components. The characteristics of the proposed LED sink driver are investigated by theoretical analysis, simulation program with integrated circuit emphasis (SPICE) simulations, and breadboard experiments. In the performed simulations, the power efficiency of the proposed driver reaches about 80 % at 500 mW when the duty factor is 0.5. Furthermore, the experiment demonstrates high voltage gains and flexible controllability of an output voltage.

Green syntheses of stable and efficient organic dyes for organic hybrid light-emitting diodes

Transmuting a natural product in chocolate into phosphors for light-emitting diodes.

Quantum Dot-Polyfluorene Composites for White-Light-Emitting Quantum Dot-Based LEDs.

Colloidal quantum dots (QDs) are a promising luminescent material for the development of next generation hybrid light-emitting diodes (QDLEDs). In particular, QDs are of great interest in terms of the development of solid-state light sources with an emission spectrum that mimics daylight. In this study, we used CdSe(core)/ZnS/CdS/ZnS(shell) QDs with organic ligands mimicking polyfluorene and its modified derivatives to obtain QD–polymer composites emitting white light. We found that the emission of the composites obtained by spin-coating, being strongly dependent on the chemical structure of the polymer matrix and the QD-to-polymer mass ratio, can be accurately controlled and adjusted to bring its emission spectrum close to the spectrum of daylight (CIE coordinates: 1931 0.307; 0.376). Moreover, the light emission of these composites has been found to be temporally stable, which is due to the minimal structural instability and volume-uniform charge and energy transfer properties. Thus, the use of the synthesized polyfluorene-based organic ligands with controllable chemical structures adaptable to the structure of the polymer matrix can significantly increase the stability of white light emission from QD composites, which can be considered promising electroluminescent materials for fabrication of white QDLEDs.

High Efficiency and Durability from Perovskite–Organic Hybrid Light-Emitting Diodes

High Efficiency and Durability from Perovskite–Organic Hybrid Light-Emitting Diodes

A hybrid LED sink driver using a nesting-type switched-inductor/switched-capacitor buck-boost converter

This paper presents a novel light emitting diode (LED) sink driver with a high voltage gain for LED-based lighting applications. Unlike conventional LED sink drivers, the proposed driver has the nested switched-inductor/switched capacitor (SI/SC) topology consisting of an SI buck-boost converter block and a nesting-type SC cell. Owing to the nested SI/SC topology, the proposed driver offers not only a high voltage gain but also a flexible controllability of the LED currents and transformer-less structure. The effectiveness of the proposed driver is justified by some simulation results in SPICE software environment and laboratory experimental tests. In the performed simulations, the proposed driver in comparison of conventional drivers improved almost 6% power efficiency when the output power was 500 mW. Furthermore, in the performed experiments, the feasibility of the proposed topology is confirmed by demonstrating a high voltage gain and the output controllability.

A Hybrid LED Driver With Improved Efficiency

A high-efficient hybrid light-emitting diode (LED) driver is introduced in this article. By combining the merits of conventional switching-converter-based and inductor-less driving solutions, the proposed topology fully utilizes the input power from the ac mains without causing considerable switching loss or excessive voltage stress. With the help of a small-size inductor and the hybrid scheme, the proposed driver automatically alternates between switching mode and linear mode as the rectified input voltage changes. In addition, the driver can be configured either in a single stage for a high power factor (PF) and high efficiency or in the second stage of a two-stage solution for alleviating harmful low-frequency flicker. The proposed driver-integrated circuit is implemented in a 0.35-μm high-voltage CMOS process and tested under 110-VAC 60-Hz input. Measurement results show that, when operating in the high PF configuration, the proposed driver achieves 95.1% power efficiency and 0.986 PF. For the low flicker configuration, it achieves 92% efficiency and 15% flicker while maintaining a 0.918 PF.