Light Recycling Research Articles

Highly Enhanced Light Recycling in Quantum Dot Displays by Sidewall Reflectors

AbstractQuantum dot (QD) color conversion‐based displays have emerged as one of the most promising next‐generation devices due to their superior emission properties in terms of color expression. To date, however, existing QD color conversion layer (QD‐CCL) technologies have suffered from low luminance and power efficiency, mainly due to significant light absorption by the bank structure. Here, the color conversion efficiency of QD‐CCL has been significantly enhanced by fabricating a highly reflective metal layer on the side surface of the bank structure. Using a high‐aspect‐ratio silver reflector fabricated through a secondary sputtering lithographic technique involving argon ion bombardment, the fabricated QD‐CCL is combined with a blue organic light‐emitting diode (OLED) serving as a light source. As a result, light recycling from the reflector significantly enhances color conversion efficiency and luminance by up to 4.60‐fold and 4.29‐fold, respectively. Optical simulation reveals that higher pixel resolution provides greater reflection probabilities during extraction. This photomask‐free approach is not only simple but also highly compatible with existing semiconductor fabrication processes, making it a viable commercial alternative for all color‐converting structures that utilize light‐emitting materials with omnidirectional emission characteristics.

Microwave-treated layered graphite for highly efficient solar-powered seawater desalination and wastewater treatment

In the midst of the global water crisis, the ‘waste-to-treasure’ strategy, which includes desalination and wastewater recycling, is proving to be a promising approach. However, existing solar evaporators are hampered by challenges such as low photothermal conversion efficiency and significant heat losses. Here, we present an innovative solution that reduces the band gap of the material and improves the efficiency of light recycling. As a result, the microwave-treated graphite achieves a 15 % reduction in reflectivity and a 9 °C increase in surface temperature. In addition, the integration of this graphite with a hydrogel to modulate the interfacial wettability further optimizes the evaporation efficiency. When exposed to sunlight, the developed cone column evaporator achieves an impressive evaporation rate of 2.91 kg m−2 h−1, which is a significant increase of 663 % over the natural evaporation rate of a 3.5 wt% NaCl solution. Remarkably, no salt deposits were observed on the surface of the evaporator during the tests and the material exhibited excellent adsorption and desorption properties for pollutants, highlighting its potential for sustainable applications. These results provide valuable theoretical and practical insights for the design and development of high-efficiency solar evaporators.

Ultra-low loss Rayleigh scattering enhancement via light recycling in fiber cladding

Rayleigh backscattering enhancement (RSE) of optical fibers is an effective means to improve the performance of distributed optical fiber sensing. Femtosecond laser direct-writing techniques have been used to modulate the fiber core for RSE. However, in-core modulation loses more transmission light, thus limiting the sensing distance. In this work, a cladding-type RSE (cl-RSE) structure is proposed, where the femtosecond laser is focused in the fiber cladding and an array of scatterers is written parallel to the core. The refractive-index modulation structure redistributes the light in the cladding, and the backward scattered light is recovered, which enhances the Rayleigh backscattered signal with almost no effect on the core light. Experimentally, it was demonstrated that in an effectual cl-RSE structure, the insertion loss was reduced to 0.00001 dB per scatterer, corresponding to the lowest value for a point scatterer to date. The cl-RSE structure accomplished measurements up to 800°C. In particular, the temperature measurement fluctuation of the cl-RSE fiber portion is only 0.00273°C after annealing. These results show that the cl-RSE structure has effective scattering enhancement, ultra-low loss, and excellent high-temperature characteristics, and has great potential for application in Rayleigh scattering-enhanced distributed fiber sensing.

Light Mo Isotopes of Post‐Collisional Ultrapotassic Rocks in Southern Tibet Derived From Subducted Indian Continental Crust

AbstractRecycling of molybdenum isotopes in continental subduction zones remains debated. In this contribution, we re‐visit the Mo isotope compositions of the Sailipu post‐collisional ultrapotassic rocks in the Himalaya‐southern Tibet orogen. These ultrapotassic rocks have very varying δ98/95Mo values of −0.66 to −0.07‰ and Mo/Ce ratios of 0.0008–0.005, which are lower than those of mid‐ocean ridge basalts (MORB; δ98/95Mo = −0.20 ± 0.06‰, and Mo/Ce = 0.03) and oceanic subduction‐related (i.e., mantle source involving fluids, residual slab, or oceanic sediments) magmatic rocks (e.g., modern arc lavas, Cenozoic OIB‐type basalts in eastern China and the central Mariana Trough basalts in the back‐arc basin, syn‐collisional andesitic rocks in southern Tibet). Combined with the light Mo isotopes of the Himalayan schists and gneisses, we suggest that the light Mo isotopic signature of the Sailipu ultrapotassic rocks is derived from subducted Indian continental crust. This is consistent with the extremely low δ11B (−17.4 to −9.7‰) and B/Nb (0.16–1) values and enriched Sr‐Nd‐Pb isotopes of the Sailipu ultrapotassic rocks. Thus, this study reveals the recycling of light Mo‐B isotopes during continental subduction and demonstrates that Mo‐B isotopes can effectively distinguish between continental and oceanic subduction.

Color Rendering Index over 95 Achieved by Using Light Recycling Process Based on Hybrid Remote-Type Red Quantum-Dot Components Applied to Conventional LED Lighting Devices.

Red color conversion materials have often been used in conventional white LEDs (light-emitting diodes) to enhance the insufficient deep-red component and thus improve the color-rendering property. Quantum dots (QDs) are one of the candidates for this due to their flexibility in controlling the emission wavelength, which is attributed to the quantum confinement effect. Two types of remote QD components, i.e., QD films and QD caps, were prepared and applied to conventional white LED illumination to improve the color-rendering properties. Thanks to the red component near 630 nm caused by the QD components, the color rendering indices (CRIs) of both Ra and R9 could be increased to over 95. It was found that both the diffusing nature of the reflector and the light recycling process in the vertical cavity between the bottom reflector and the top optical films play important roles in improving the color conversion efficiency of remote QD components. The present study showed that the proper application of remote QDs combined with a suitable optical cavity can control the correlated color temperature of the illumination over a wide range, thus realizing different color appearances of white LED illumination. In addition, a high CRI of over 95 could be achieved due to the sufficient excitation from fewer QDs, due to the strong optical cavity effect.

Corrections to “Tripling Light Conversion Efficiency of μLED Displays by Light Recycling Black Matrix”

Quantum-dot color conversion film (QDCCF) with a partitioned black matrix (BM) realizes effective color generation with low crosstalk for micro-light-emitting diode (μLED) displays. However, this traditional BM seriously deteriorates light conversion efficiency (LCE) of QD converted μLED displays due to its absorption energy loss. In this paper, a novel internal and external reflective black matrix (IERBM) is proposed to improve the LCE and blue light utilization (BLU) by light recycling and reuse. Based on the IERBM structural optimization, the LCE can be respectively improved by 3.39× and 2.74× for red and green QDCC sub-pixels, and the BLU can be effectively increased by 1.11×. Accurate white balance and high color uniformity are achieved by this μLED display. Meanwhile, both the crosstalk of 1.72% and the color gamut of 89.8% Rec. 2020 are comparable with traditional absorptive BM. It is also found that the proposed IERBM has the potential to weaken μLED's sidewall effect. This work may open up a new technological route for improving the optical performance in advanced self-emissive displays.

Wide Bandgap Perovskite Photovoltaic Cells for Stray Light Recycling in a System Emitting Broadband Polarized Light

AbstractPerovskite based photovoltaic (PV) cells are unique in combining low open‐circuit voltage losses with a broad bandgap tunability. This makes them an ideal PV cell to recycle photons back into electrical power in a variety of illumination systems or light emitting devices. Here, advantage of these features is taken and wide bandgap (WBG) perovskite PV cells are incorporated in devices suitable for display illumination and demonstrate a high yield in stray light recycling back into electricity with up to a 37.5% power conversion efficiency. The specific device considered is a modified half‐cylinder photonic plate designed to emit diffused broadband polarized light using a nonabsorbing reflective polarizer based on a random dielectric layer distribution. It is experimentally demonstrated that light recycling using appropriately tuned WBG perovskite PV cells becomes very efficient when implemented in systems where the light is emitted from narrowband sources, even if the emission spans a broad wavelength range.

Tripling Light Conversion Efficiency of μLED Displays by Light Recycling Black Matrix

Quantum-dot color conversion film (QDCCF) with a partitioned black matrix (BM) realizes effective color generation with low crosstalk for micro-light-emitting diode (μLED) displays. However, this traditional BM seriously deteriorates light conversion efficiency (LCE) of QD converted μLED displays due to its absorption energy loss. In this paper, a novel internal and external reflective black matrix (IERBM) is proposed to improve the LCE and blue light utilization (BLU) by light recycling and reuse. Based on the IERBM structural optimization, the LCE can be respectively improved by 3.39× and 2.74× for red and green QDCC sub-pixels, and the BLU can be effectively increased by 1.11×. Accurate white balance and high color uniformity are achieved by this μLED display. Meanwhile, both the crosstalk of 1.72% and the color gamut of 89.8% Rec. 2020 are comparable with traditional absorptive BM. It is also found that the proposed IERBM has the potential to weaken μLED's sidewall effect. This work may open up a new technological route for improving the optical performance in advanced self-emissive displays.

Inverse-designed waveguide-based biosensor for high-sensitivity, single-frequency detection of biomolecules

Abstract Integrated silicon photonic waveguide biosensors have shown great potential for detecting bio-molecules because they enable efficient device functionalization via a well-developed surface chemistry, as well as simple scalable manufacturing, which makes them particularly suitable for low-cost point-of-care diagnostic. The on-chip integrated biosensors can be broadly classified into two types: (i) high-quality factor resonator sensors and (ii) interferometric sensors relying on non-resonant optical elements such as e.g. integrated waveguides. The former type usually requires a broadband or a tunable light source as well as complicated signal post-processing to measure a shift of the resonance frequency, while the latter exhibits a relatively low sensitivity due to the lack of efficient light recycling and phase accumulation mechanism in low quality factor elements. Additionally, high quality factor resonant photonic structures can be very sensitive to the presence of other non-target molecules in the water solution, causing sensor vulnerability to any noise. In this work, we combine a computational “inverse design” technique and a recently introduced high-contrast probe cleavage detection (HCCD) technique to design and optimize waveguide-based biosensors that demonstrate high sensitivity to the target molecule while being less sensitive to noise. The proposed biosensors only require a single frequency (or narrow-band) source and an intensity detector, which greatly simplifies the detection system, making it suitable for point-of-care applications. The optimal integrated sensor design that we demonstrate shows 98.3% transmission for the positive (target detected, probes cleaved) state and 4.9% transmission for the negative (probes are still attached) state at 1550 nm wavelength. The signal intensity contrast (20.06-fold transmission increase) shown in this work is much greater than the shift of the resonance frequency (less than 1% wavelength shift) observed in conventional ring-resonator-based biosensors. The new design may pave the way for realizing a single-frequency highly sensitive and selective optical biosensor system with a small physical footprint and a simple optical readout on a silicon chip.

Design of a complex of medical service robots and analysis of transmission characteristics of drives

The article describes a complex of robots designed and manufactured at the Institute of Mechanics and Machine Science for a hospital environment, consisting of a transport robot and two functional robots: assistant robot and a disinfection robot. The assistant robot is designed to measure temperature and blood pressure, automate the transportation of medicines, bed linen, food, etc. using a transport robot. With the help of a scissor mechanism the assistant robot is able to adjust the height of the trays, devices for measuring temperature and blood pressure. The disinfection robot is designed to automate disinfection in enclosed spaces. UV lamps with rotating 180 degrees reflectors, allow the disinfection robot to work in two modes: direct irradiation of the room with ultraviolet light and air recycling. There is also a mode of spraying disinfectant liquid. The article describes the design of a transport robot, an assistant robot and a disinfection robot, and shows the results of experimental studies.

Efficient, high-CRI white LEDs by combining traditional phosphors with cadmium-free InP/ZnSe red quantum dots

Quantum dots (QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode (LED) configurations. Earlier studies showed that the spectral efficiency of white LEDs with high color rendering index (CRI) values could be considerably improved by replacing red-emitting nitride phosphors with narrowband QDs. However, the red QDs in these studies were cadmium-based, which is a restricted element in the EU and certain other countries. The use of InP-based QDs, the most promising Cd-free alternative, is often presented as an inferior solution because of the broader linewidth of these QDs. However, while narrow emission lines are the key to display applications that require a large color gamut, the spectral efficiency penalty of this broader emission is limited for lighting applications. Here, we report efficient, high-CRI white LEDs with an on-chip color converter coating based on red InP/ZnSe QDs and traditional green/yellow powder phosphors. Using InP/ZnSe QDs with a quantum yield of nearly 80% and a full width at half-maximum of 45 nm, we demonstrate high spectral efficiency for white LEDs with very high CRI values. One of the best experimental results in terms of both luminous efficacy and color rendering performance is a white LED with an efficacy of 132 lm/W, and color rendering indices of R a ≈ 90 , R 9 ≈ 50 for CCT ≈ 4000 K . These experimental results are critically compared with theoretical benchmark values for white LEDs with on-chip downconversion from both phosphors and red Cd-based QDs. The various loss mechanisms in the investigated white LEDs are quantified with an accurate simulation model, and the main impediments to an even higher efficacy are identified as the blue LED wall-plug efficiency and light recycling in the LED package.

Nestin promotes pulmonary fibrosis via facilitating recycling of TGF-β receptor I.

BackgroundIdiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that is characterised by aberrant proliferation of activated myofibroblasts and pathological remodelling of the extracellular matrix. Previous studies have revealed that the intermediate filament protein nestin plays key roles in tissue regeneration and wound healing in different organs. Whether nestin plays a critical role in the pathogenesis of IPF needs to be clarified.MethodsNestin expression in lung tissues from bleomycin-treated mice and IPF patients was determined. Transfection with nestin short hairpin RNA vectors in vitro that regulated transcription growth factor (TGF)-β/Smad signalling was conducted. Biotinylation assays to observe plasma membrane TβRI, TβRI endocytosis and TβRI recycling after nestin knockdown were performed. Adeno-associated virus serotype (AAV)6-mediated nestin knockdown was assessed in vivo.ResultsWe found that nestin expression was increased in a murine pulmonary fibrosis model and IPF patients, and that the upregulated protein primarily localised in lung α-smooth muscle actin-positive myofibroblasts. Mechanistically, we determined that nestin knockdown inhibited TGF-β signalling by suppressing recycling of TβRI to the cell surface and that Rab11 was required for the ability of nestin to promote TβRI recycling. In vivo, we found that intratracheal administration of AAV6-mediated nestin knockdown significantly alleviated pulmonary fibrosis in multiple experimental mice models.ConclusionOur findings reveal a pro-fibrotic function of nestin partially through facilitating Rab11-dependent recycling of TβRI and shed new light on pulmonary fibrosis treatment.

Energy recycling under ambient illumination for internet-of-things using metal/oxide/metal-based colorful organic photovoltaics

Colorful indoor organic photovoltaics (OPVs) have attracted considerable attention in recent years for their autonomous function in internet-of-things (IoT) devices. In this study, a solution-processed TiO2 layer in a metal–oxide–metal (MOM) color filter electrode is used for light energy recycling in P3HT:ICBA-based indoor OPVs. The MOM electrode allows for tuning of the optical cavity mode to maximize photocurrent production by modulating the thickness of the TiO2 layer in the sandwich structure. This approach preserves the OPVs’ optoelectronic properties without damaging the photoactive layer and enables them to display a suitable range of vivid colors. The optimized MOM-OPVs demonstrated an excellent power conversion efficiency (PCE) of 8.8% ± 0.2%, which is approximately 20% higher than that of reference opaque OPVs under 1000 lx light emitting diode illumination. This can be attributed to the high photocurrent density due to the nonresonant light reflected from metals into the photoactive layer. Additionally, the proposed MOM-OPVs exhibited high external quantum efficiency and large parasitic shunt resistances, leading to improved fill factor and PCE values. Thus, the study’s MOM electrode provides excellent feasibility for realizing colorful and efficient indoor OPVs for IoT applications.

Light recycling in LED-pumped Ce:YAG luminescent concentrators.

We report the development of a high-brightness, high-power Ce:YAG luminescent concentrator pumped by 2240 blue LEDs in quasi-continuous wave operation (10 µs, 10 Hz). Using light confinement and recycling in the three space dimensions, the parallelepiped (1mm×14×mm×200mm) Ce:YAG emits a power of 145 W from a square output surface (1 × 1mm2) corresponding to a brightness of 4.6 kW/cm2/sr. This broadband yellow source has a unique combination of luminous flux (7.6 104 lm) and brightness (2.4 104 cd/mm2) and overcomes many other visible incoherent sources by one order of magnitude. This paper also proposes a deep understanding of the performance drop compared to a linear behavior when the pump power increases. Despite excited state absorption was unexpected for this low doped Ce:YAG pumped at a low irradiance level, we demonstrated that it affects the performance by tripling the losses in the concentrator. This effect is particularly important for small output surfaces corresponding to strong light recycling in the concentrator and to average travel distances inside the medium reaching meters.

Slot-Die-Coated Ternary Organic Photovoltaics for Indoor Light Recycling

Efficient organic photovoltaics (OPVs) based on slot-die-coated (SD) ternary blends were developed for low-intensity indoor light harvesting. For active layers processed in air and from eco-friendly solvents, our device performances (under 1 sun and low light intensity) are the highest reported values for fluoro-dithiophenyl-benzothiadiazole donor polymer-based OPVs. The N-annulated perylene diimide dimer acceptor was incorporated into a blend of donor polymer (FBT) and fullerene acceptor (PC61BM) to give ternary bulk heterojunction blends. SD ternary-based devices under 1 sun illumination showed enhanced power conversion efficiency (PCE) from 6.8 to 7.7%. We observed enhancement in the short-circuit current density and open-circuit voltage of the devices. Under low light intensity light-emitting device illumination (ca. 2000 lux), the ternary-based devices achieved a PCE of 14.0% and a maximum power density of 79 μW/cm2 compared to a PCE of 12.0% and a maximum power density of 68 μW/cm2 for binary-based devices. Under the same illumination conditions, the spin-coated (SC) devices showed a PCE of 15.5% and a maximum power density of 88 μW/cm2. Collectively, these results demonstrate the exceptional promise of a SD ternary blend system for indoor light harvesting and the need to optimize active layers based on industry-relevant coating approaches toward mini modules.

Study of mechanical and morphological properties of jute-tea leaf fiber reinforced hybrid composites: Effect of glass fiber hybridization

Fiber reinforced plastic composites replace wood and metals due to their light weight, high strength to weight ratio, noncorrosive nature and stiffness. Bio based fibers are used in place of petroleum based fibers because of environmental concerns. Natural fibers exhibit low specific strength and light density, processing and recycling are simple. New materials are being developed and grow every day. The high strength, light weight and biodegradability of natural fiber composites such as sisal, jute, kenaf, snake grass and banana fiber has made polymer composites were more attractive. The fiber is subjected to chemical pretreatments using alkali treatment (mercerization). This research has created composites of glass-jute-tea leaf fiber-reinforced polymers and assessed their mechanical characteristics such as tensile, flexural and impact test. Scanning Electron Microscopy (SEM) is being used to evaluate the interfacial characteristics, inner cracks and inner structures of broken surfaces. The experimental results showed 10% glass fiber, 20% jute fiber and 10% tea leaf fiber produced the optimum mechanical properties and it can be alternative material for pure glass fiber reinforced polymer composite.

Tailoring Triple‐Anion Perovskite Material for Indoor Light Harvesting with Restrained Halide Segregation and Record High Efficiency Beyond 36%

AbstractIndoor photovoltaics are promising to enable self‐powered electronic devices for the Internet of Things. Here, reported is a triple‐anion CH3NH3PbI2−xBrClx perovskite film, of which the bandgap is specially designed for indoor light harvesting to achieve a record high efficiency of 36.2% with distinctive high open circuit voltage (Voc) of 1.028 V under standard 1000 lux fluorescent light. The involvement of both bromide and chloride suppresses the trap‐states and nonradiative recombination loss, exhibiting a remarkable ideality factor of 1.097. The introduction of chloride successfully restrains the halide segregation of iodide and bromide, stabilizing the triple‐anion perovskite film. The devices show an excellent long‐term performance, sustaining over 95% of original efficiency under continuous light soaking over 2000 h. These findings show the importance and potential of I/Br/Cl triple‐anion perovskite with tailored bandgap and suppressed trap‐states in stable and efficient indoor light recycling.

Modeling TPV Devices Based on Exact Analytical Solution of the Generalized Shockley – Queisser Model

Exact solution of the generalized Shockley – Queisser model provides simple and effective tool for modeling of photovoltaic (PV) and thermophotovoltaic (TPV) devices with advanced photonic management. This formalism takes into account spectral characteristics of absorption/emission and a variety of recombination processes in semiconductor cell. In the current work we generalize this formalism to devices with non-ideal light reflectors used for light recycling and trapping. As an example, we investigate effects of the light management in InGaAsSb TPV converters (0.53 eV bandgap) with back surface reflector and with an additional front surface scattering layer, which provides Lambertian trapping of photons. We calculate the output power (efficiency) and investigate tradeoff between photon absorption and Auger recombination processes as a function of the device thickness. Finally, we compare performance of these TPV devices with the performance of traditional devices.

Fabrication of dye-sensitized solar cells using a both-ends-opened TiO 2 nanotube/nanoparticle hetero-nanostructure

Abstract We fabricated a hetero-structure photoanode with both-ends-opened TiO2 nanotubes and TiO2 nanoparticles for dye-sensitized solar cells (DSSCs). Two-step anodization and selective etching process were used to obtain the both-ends-opened TiO2 nanotubes. A heat treatment was employed to obtain anatase crystal-structured nanotubes. The effect of the both-ends-opened TiO2 nanotubes on the photoelectric conversion efficiency (PCE) of the DSSCs was evaluated by positioning the TiO2 nanotubes on TiO2 nanoparticle layers and by sandwiching them between the TiO2 nanoparticles. It is suggested that both-ends-opened TiO2 nanotubes serve as incident light scattering layers that lead to superior light harvesting efficiency of DSSCs. This increases the electron lifetime and results in the recycling of more light by dye molecules, thus increasing the photocurrent density. Consequently, a high PCE of 7.74% was obtained when the TiO2 nanotubes were placed on the TiO2 nanoparticles and a PCE of 8.56% was obtained when the TiO2 nanotubes were placed between the TiO2 nanoparticles.

Self-sufficient energy recycling of light emitter diode/thermoelectric generator module for its active-cooling application

This paper presents the energy recycling and self-sufficient application of a novel high-power light emitting diode integrating with a thermoelectric generator module. The proposed lighting module in which a thermoelectric generator device is sandwiched between light emitting diode device and heat sink autonomously recycles the waste heat to self-sufficiently support for its active cooling with an electrical fan. The start-up responses of illuminance, temperature, current and power for the proposed module were evaluated through experimental measurement. The corresponding mathematical model was derived and simulation model was built using MATLAB/Simulink for verification. The illuminance, electrical, and thermal performances have a close agreement between experiment and simulation results. The technological viability about both autonomous operation and self-sufficient energy recycling for the novel module with the active cooling was validated. Compared with passive-cooling devices, the proposed module declines the working temperature and improves illuminance simultaneously.