Light Conversion Film Research Articles

Core-Shell Confined Stable Polymer Nanoparticles with Tunable Clusteroluminescence.

Clusteroluminescent polymers have the most potential to be used in light conversion agricultural films due to tunable emission wavelength and large-scale production, but they are still limited by shortcomings such as poor stability and sensitivity to melting processes. In this work, we propose a core-shell confined stable clusteroluminescent polymeric nanoparticle strategy with adjustable shell thickness. By the employment of a combination of solvent and heat treatment methods, the structures, rigid-flexible properties, and aggregation states of the core polymer chains have been modified. The presence of cross-linked shells has significantly enhanced the stability of the clusteroluminescent nanoparticles, ensuring that they retain their structure form even after undergoing high temperature and shear. Finally, the stable agricultural light conversion films with tunable clusteroluminescence are obtained via melt blending of the core-shell confined nanoparticles and polyethylene (PE). Due to the shell confinement effect, when melt-blended, the shell can protect the clusteroluminescent polymer within the core from the effects of high temperature and shear. It is anticipated that the completion of this work will provide a significant foundation for the large-scale application of cluster-luminescent polymers in agriculture.

Realization of blue-red dual-emission via energy transfer in Na3KMg7(PO4)6: Eu2+, Mn2+ phosphor for plant growth application☆

A blue-red dual-emitting phosphor, Na3KMg7(PO4)6: Eu2+, Mn2+ was developed in this study. Eu2+ acts as a sensitizer ion in Na3KMg7(PO4)6: Mn2+, which significantly improves the undesirable luminous efficiency of Mn2+. The energy transfer between Eu2+ and Mn2+ significantly boosts both internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the phosphor, achieving values of 72.5% and 42.6%, respectively. Additionally, the phosphor demonstrates exceptional thermal stability, at 150 °C, maintaining 71.49% of its initial emission intensity. The emission spectrum of the phosphor closely matches the chlorophyll’s absorption spectra, with similarities of 75.06% and 94.52%, respectively. This was further confirmed through a fabricated LED with a n-UV chip (395 nm). To further assess the potential for agritech applications, a light-conversion film incorporating the developed phosphor in PDMS glue was prepared. An outdoor cultivation trial with Chlorella showed that the algae's growth rate improves by 27.3% relative to a control group. These results reveal the significant potential of the Na3KMg7(PO4)6: Eu2+, Mn2+ phosphor for enhancing plant growth in practical applications.

Enhanced luminescence performance in double perovskite CaSrLaSbO6: Mn4+ red emission phosphors for indoor plant growth via cation doping

Novel CaSrLaSbO6: Mn4+ red-emitting phosphors with double perovskite structure were successfully synthesized by the high-temperature solid-phase method. CaSrLaSbO6:Mn4+ phosphor showed a broad excitation band with different excitation peaks from 250 nm to 600 nm owing to the Mn4+-O2- charge transfer and 4A2g → (4T1g, 2T2g, and 4T2g) transitions of Mn4+ ions and exhibited intense deep-red emission at 678 nm attributed to the 2Eg → 4A2g transition of Mn4+ ions. To further enhance the performance of the phosphor, a cation doping method was adopted in this paper to synthesize CaSrLa1-xLnxSbO6: Mn4+ (Ln = Gd, Y) phosphors. The luminescence intensity of the samples was enhanced after doping with different cations, and the related mechanism was discussed. In addition, the microstructure and crystal field environment were systematically investigated. The luminescence intensity of the CaSrLa0.85Y0.15SbO6: Mn4+ phosphor was about 1.82 times higher than that of CaSrLaSbO6: Mn4+phosphor. The emission spectrum of the sample matched well with the absorption band of plant pigments. Furthermore, the plant growth LEDs and light-conversion film were prepared by using the optimized CaSrLa0.85Y0.15SbO6: Mn4+. The results indicate that the designed phosphors have great potential applications in agricultural cultivation.

Design of Boron- and Nitrogen-Codoped Carbon Dots with Dual-Emission Performance toward Sustainable Light-Conversion Films

Design of Boron- and Nitrogen-Codoped Carbon Dots with Dual-Emission Performance toward Sustainable Light-Conversion Films

Ultraviolet-to-Blue Light Conversion Film Affects Both Leaf Photosynthetic Traits and Fruit Bioactive Compound Accumulation in Fragaria × ananassa

The influence of light downconversion films (red, pink and blue films) on leaf physiological features and fruit bioactive compound accumulation was studied in strawberry plants. Red, pink and blue films were able to convert light less utilised by plants into more efficient light wavebands with various possibilities depending on the film characteristics (blue film shifts UV into blue radiation; red film shifts green into red radiation, pink film shifts UV and green into blue and red radiation but to a lesser extent than red film). Indeed, by enhancing the quality of light available for photosynthesis, the utilization of these films holds the potential to improve agricultural productivity and sustainability. All of these light downconversion films resulted in higher plant fresh weight compared to a control colourless (Cnt) film, with plants grown under blue film (UV-to-blue light conversion) showing the most impressive results in terms of total leaf area (+25%), leaf thickness (+10%) and leaf mass per area (+15%). Simultaneously, during the flowering stage, plants under blue film had a higher net photosynthetic rate due to the increase in photosynthetically efficient wavelengths. Moreover, blue film resulted in the highest total phenolic (+40% and +28% than red and pink films, respectively) and flavonoid content (+54%, +84%, +70% than Cnt, red and pink films, respectively) in fruit, with specific effects on targeted phenols, i.e., quercetin, ellagic acid and its glycoside, ellagitannins, and procyanidins. In conclusion, the use of the UV-to-blue conversion light film tested herein represents an innovative solution to increase strawberry yield and promote fruit nutraceutical features, playing a pivotal role in ensuring food quality and security and sustainable agricultural practices.

Spray pyrolysis synthesis of Sr2Si5N8:Eu2+ nanoparticles for light conversion film enhancing photosynthesis in greenhouses

This study presents a comparative analysis of Sr2Si5N8:Eu2+ nanoparticles synthesized using Spray Pyrolysis (SP) and Solid-State Synthesis (SSS). Through meticulous characterization, we found that the SP method significantly enhanced the morphological and optical properties of the nanoparticles. SP-produced nanoparticles demonstrated a 30% higher crystallinity and a 25% increase in luminescence intensity compared to their SSS counterparts. Additionally, the mesoporous structure characteristic of SP-synthesized particles exhibited a 15% greater surface area, measured at 124.7 m2 g−1, which contributed to improved light absorption capabilities. These attributes are crucial for the intended application of enhancing photosynthesis in greenhouse environments. The UV–Visible spectra confirmed that SP nanoparticles possess superior light conversion capabilities, with notable implications for optimizing light distribution to facilitate plant growth. This research highlighted the advantages of SP, including ease of scalability and enhanced optical performance, which are pivotal for agricultural applications. The study emphasized that the choice of synthesis method played a critical role in tailoring the properties of Sr2Si5N8:Eu2+ nanoparticles for specific functional requirements in optical and agricultural technologies.

Polyvinyl alcohol covalently grafted perylene imide for high-performance light-conversion film

To suppress the aggregation caused quenching of perylene diimide (PDI) derivatives, and improve photostability of PDI derivatives, a polyvinyl alcohol grafted copolymer (PVA-PDIE) was prepared by transesterification of a perylene imide derivative (PDIE) and polyvinyl alcohol (PVA). PDIE was characterized by H-NMR and HR-MS, and PVA-PDIE was confirmed by IR, water resistance, and control experiments. PVA-PDIE film showed high quantum yield (0.75), and matching emission maxima (620 nm). More importantly, PVA-PDIE film had excellent thermal stability and photostability, high transmittance and light conversion quality. Furthermore, the decomposition temperature of PVA-PDIE film was up to 240 °C, while emission intensity maintained at 95 % and 96 % of the initial value in turn after intensified ultraviolet radiation of 40 h and sunlight radiation of 40 days. Compared with the PVA blank film, photosynthetic photon flux density (PFD) of PVA-PDIE film increased by 25 % and 34 % for red orange light and near-infrared light respectively, and decreased by 39 %, 27 %, and 24 % for ultraviolet light, blue violet light, and yellow-green light in sequence, indicating outstanding light conversion performance. Meanwhile, PVA-PDIE film had excellent transparency.

Enhancement of biomass, lipid accumulation, and carbon sequestration potential in microalgae via cultivation with Aggregation-Induced emission Light-Conversion films

Microalgae are a kind of promising raw material for bioenergy production and carbon sequestration. To enhance cell growth and production efficiency, great efforts were made for exploring the appropriate intensity and quality of light to improve the synthesis of the value-added products. The aggregation-induced emission (AIE) material (Astrazon Brilliant Red 4G), active for converting blue-green light to red light (630–680 nm), was for the first time applied in the research to achieve high fatty acid yield with considerable carbon–neutral ability. After 10 days-incubation, it revealed that AIE light-converting films boosted the biomass of microalgae Scenedesmus obliquus, Phaeodactylum tricornutum, and Chlamydomonas reinhardtii by 13.00 %, 28.00 %, and 26.00 %, and the total lipid contents increased by 34.60 %, 17.74 %, and 22.63 %, with the carbon sequestration capacity raised by 17.18 %, 38.89 %, and 35.71 %. Furthermore, AIE light-converting films promoted the accumulation of unsaturated fatty acids (UFAs) in all three microalgae. Our study demonstrated the potential application of AIE light-converting films for cultivating microalgae to capture high carbon dioxide for photosynthesize carbon–neutral energy and high-valued active compounds.

Silanized carbon quantum dots assembled porous glass and its luminescent properties

In this paper, the silanized carbon quantum dots (Si CQDs) were assembled into nano-porous glass (NPG) by solution ultrasonic method. The morphology, structure, elementary composition, luminescence properties, water-resistance and anti-ultraviolet properties were systematically studied. Concentration quenching occurs when the Si CQDs doping content exceeds 7.73 mg/g. It is found that nano-porous glass matrix can effectively disperse and protect the Si CQDs, which realizes the luminescence of Si CQDs in solid state and enhances the fluorescence emission intensity of Si CQDs. In addition, the spatial confinement effect of nano-channels in Si CQDs/NPG composites makes it obtain excellent water-resistance. At the same time, the composites show better photo-stability under continuous UV irradiation. The above results provide a basis for its application in agricultural light conversion films.

Short wavelength light absorption and conversion films containing carbon nanodots for light damage prevention

The carbon nanodots (CNDs) can absorb short wavelength light and enable excited electrons to achieve light conversion to long wavelength emission by radiative transition, while accompanying the non-radiative transition of excited electrons, in order to block the short wavelength light. The CNDs were prepared from chitosan as the carbon source, and then mixed with polyvinyl alcohol (PVA) to prepare CNDs-based optical blocking films (CND-OBFs) containing different proportions of CNDs. Images were clearly visible through CND-OBFs under both close and long-distance observation, demonstrating good transparency. The CND-OBFs were shown to block both UV light from sunlight and harmful blue light from computers, mobile phones and white light-emitting diodes. The CND-OBFs can thus be used to effectively block short wavelength light. Samples of wood were covered with different CND-OBFs and the wood surfaces were then irradiated with UV light (340 nm, 80 W). The results show that different CND-OBFs block short wavelength light to different extents; CND-OBF containing 15.7 % CNDs can completely block short wavelength light through absorption and conversion, protecting the wood samples from discoloration. This work provides a new research approach in which CNDs are used to protect wood by blocking short wavelength light.

Potential usage of cesium manganese halide for multi-functional optoelectronic devices: Display & photodetector application

The composition of manganese, which exhibits tetrahedral coordination with halogen ligands, makes it excellent for use in green light-emitting materials. In particular, zero-dimensional Cs3MnBr5 material has continuously been researched as a lead-free all-inorganic light emitting material. It has excellent optical properties such as center wavelength and full width at half maximum. The most recent studies on Cs3MnBr5 have synthesized it using a bottom-up method. However, the problem of notably poor particle uniformity or efficiency remains. The aim of this study was to develop sub-micron-sized Cs3MnBr5 particles with octahedron or truncated shapes by modifying the existing hot-injection synthesis method. Sub-micron Cs3MnBr5 particles showed 60% photoluminescence quantum yield (PLQY) under blue light excitation and absorbed light in the entire visible light region, including the absorption edge by PLE. Therefore, we explored existing research on light conversion films for LED & micro-LED and photodetector applications with a focus on optical properties of Cs3MnBr5 particles.

Luminescent properties of Eu (III) complexes with carboxylate ligands and their light conversion films

This study reports the synthesis and characterization of four europium (III) complexes with different carboxylate ligands, namely 2-pyridine-acrylic acid (H2-PA), 2-pyridine-carboxylic acid (HPic), benzoic acid (HBen), and cinnamic acid (HCin), as well as a binuclear europium-lanthanum complex with HCin as the only ligand. The obtained complexes and the light conversion films prepared from them were extensively characterized by various techniques, including elemental analysis, infrared spectroscopy (IR), X-ray single crystal diffraction, thermogravimetric analysis (TGA), and fluorescence spectroscopy. Efforts were made to systemically investigate the structural, coordination, photophysical, and thermal properties of the luminescent materials, and elucidate the correlations between the ligand triplet energy levels and the luminescent properties of the complexes. The results reveal that the introduction of LaIII cannot only enhance the luminescent intensity of the light conversion agent and corresponding film, but also have obvious effect on enhancing the ultraviolet aging resistance of the light conversion film. Moreover, the proper doping concentration (0.5%) of the EuIII complex La-Eu-Cin in film may better balance the properties and cost.

An innovative strategy: ultra-stable alkaline earth modified CsPbBr3 quantum dots glass was prepared by washing-heat cycle for high definition backlight display

All-inorganic perovskite quantum dots (QDs) as high-quality materials for backlight display are still limited by their own low stability. Herein, the crystallization of CsPbBr3 (CPB) QDs in a glass matrix was promoted by modifying the glass network structure with alkaline earth metals (Mg, Ca, Sr, Ba). What's more, a washing-heat treatment cycle strategy was used to optimize the best-modified sample (CPB–Mg). Among them, CPB-12Mg (add 12% MgO) showed a high photoluminescence quantum yield (PLQY = 62%) after the cycling process. More surprisingly, the six-step washing-heat treated-sample (CPB–12Mg-6) showed excellent stability. When CPB-12Mg-6 was irradiated for 240 h at 60°C, 90% relative humidity (RH), and 880 W/m2 blue light power (60°C, 90% RH, 880 W/m2), the original 90% fluorescence emission could still be maintained. Subsequently, a series of CPB-12Mg-6/CsPbBr1.5I1.5@PS light conversion films were prepared by the master batch blending method. The backlight conversion film for liquid crystal display (LCD) achieves a wide color gamut that covers 126% of the NTSC 1953 and 93.6% of the Rec.2020 standard. This innovative washing-heat treatment cycle strategy provides a new idea for improving the stability of perovskite quantum dots.

Ag Nanoparticles Optimized the Optical Properties and Stability of CsPbBrI2 Glass for High Quality Backlight Display

All-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) have generated significant attention in the emerging display industry because of their narrow-band emission, high color purity, and facile preparation and processing. By controlling the deposition of Ag nanoparticles in the B–Si–Zn glass matrix, CsPbBrI2 NC glass with significantly enhanced photoluminescence (PL) intensity (about 6.3 times) was successfully prepared, and the photoluminescence quantum yield (PLQY) is increased from 12.4% to 36.9%. More meaningfully, the high-performance glass powders were incorporated into polystyrene (PS) films through solution and blending techniques, and the films prepared by the latter had superior color coordinates and environmental stability, particularly the intense blue light stability. Under conditions of 60 °C, 90% relative humidity (RH), and 10 000 nit blue light irradiation for 40 d, the PL intensity decline rate of blended film does not exceed 5%. In addition, the light conversion film based on Ag@CsPbBrI2 glass with CsPbBr3 glass powders exhibits a wide color gamut of 125.2% of the NTSC 1953 standard, which shows richer colors than commercial displays on the liquid crystal display (LCD) screen, further opening the space for the development of the quantum dot film industry.

Fine adjustment of emission wavelength, light-conversion quality, photostability of blue-violet light conversion agents based on FRET effect

Single fluorescent chromophore is difficult to achieve efficient photoecological effect, meanwhile, the cost of light conversion agent should be more strictly controlled, thereby promoting the large-scale application of light conversion agricultural film. To solve the above problems, three carbazole derivatives CZ, TCZ and MCZ as donors of Förster resonance energy transfer, and the tris(carbazolyl) substituted triazine TPT as an acceptor of Förster resonance energy transfer, were designed and synthesized. Based on absorption and emission spectra, aggregation induced emission experiments, and light conversion quality tests, the best formulation of light conversion film are obtained. Among of them, TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films (40% ethylene vinyl alcohol copolymer defined as EVAb film) show highest photosynthetic photon flux density at 400–500 nm, and matching fluorescence emission (458 nm and 461 nm). Under 20 h of intensified ultraviolet radiation (365 nm, 40 W), the emission intensity of TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films can maintain over 94% of the initial value, showing excellent photostability. Compared with the blank EVAa/EVAb film, the transmittance of the doping films at 500–600 nm are up to 95.12%–99.64%, meaning excellent compatibility and dispersion of light conversion agent in doping films. It is worth mentioning that emission maxima of doping films can be continuously adjusted within the spectral range 430–480 nm, which is conducive to meet the photoecological needs of different crops. Finally, the doping films show low transmittance (1.78%–11.42%) at 200–350 nm, outlining excellent UV light conversion properties.

Recent Advances in Light-Conversion Phosphors for Plant Growth and Strategies for the Modulation of Photoluminescence Properties.

The advent of greenhouses greatly promoted the development of modern agriculture, which freed plants from regional and seasonal constraints. In plant growth, light plays a key role in plant photosynthesis. The photosynthesis of plants can selectively absorb light, and different light wavelengths result in different plant growth reactions. Currently, light-conversion films and plant-growth LEDs have become two effective ways to improve the efficiency of plant photosynthesis, among which phosphors are the most critical materials. This review begins with a brief introduction of the effects of light on plant growth and the various techniques for promoting plant growth. Next, we review the up-to-date development of phosphors for plant growth and discussed the luminescence centers commonly used in blue, red and far-red phosphors, as well as their photophysical properties. Then, we summarize the advantages of red and blue composite phosphors and their designing strategies. Finally, we describe several strategies for regulating the spectral position of phosphors, broadening the emission spectrum, and improving quantum efficiency and thermal stability. This review may offer a good reference for researchers improving phosphors to become more suitable for plant growth.

High Quantum Efficiency Zn2+ Doped Lead Manganese Halide @PET Film Used for Wide Color Gamut Backlit Display

AbstractOrganic–inorganic manganese halide with environmentally friendly properties has become a new candidate material for backlight display applications. In this article, tetraethylammonium bromide (C8H20N)2MnBr4 is synthesized by a simple room temperature evaporation method. The tetrahedral coordinated Mn2+ demonstrates a green emission peak at 523 nm and a commendable photoluminescence quantum yield (PLQY) of 81.7%. To improve its stability, different proportions of Zn2+ are incorporated, leading to the discovery of (C8H20N)2Mn0.95Zn0.05Br4 as the most stable variant with a high PLQY of 84.3%. Additionally, by utilizing a sandwich method and double‐layer polyethylene terephthalate (PET) film encapsulation, the powder‐to‐binder ratio and thickness gradient are optimized, resulting in the ideal (C8H20N)2Mn0.95Zn0.05Br4@PET film with a powder‐to‐binder ratio of 1:2 and a thickness of 0.5 mm. Remarkably, the film exhibits superior stability against water, heat, and photo degradation. Finally, the light conversion film prepared from (C8H20N)2Mn0.95Zn0.05Br4@K2SiF6: Mn4+@PET composite material is applied to backlight display, and the color gamut covers 112% of NTSC 1953 and 83% of Rec. 2020. This study provides a feasible route for developing environmentally friendly, low‐cost, and high‐performance liquid crystal displays.

Solvent-free rapid synthesis of carbon nanodots at atmospheric pressure: Preparation of transparent light conversion films with ultrahigh efficient UV and blue light shielding

In this age of technology, people are inevitably surrounded by electronic devices and light-emitting devices, but the radiation generated by these devices is very harmful to humans. Therefore, it is crucial to develop a stable absorbing material with efficient absorption capacity for UV and high-energy blue light (HEBL). In this paper, we report that carbon nanodots (CDs) with strong absorption peaks in the UV and HEBL can be rapidly synthesized in large scale by simply heating urea and citric acid at high temperature under atmospheric pressure without using any solvents. Interestingly, the large-scale prepared CDs possess green fluorescence emission upon excitation in both the UV and HEBL regions, exhibiting good photoconversion ability. Furthermore, ultrahigh efficient UV and HEBL shielding films can be prepared by embedding the CDs in a carboxymethyl cellulose matrix. By characterizing their transmission and absorption spectra, it can be found that the cellulose films containing 0.2 wt% CDs achieve almost complete shielding of UV-A, UV-B, and HEBL with a guaranteed visible light (550 nm) transmission rate of 80% or above. Finally, this cellulose film was further attached to a light-emitting diode (LED) chip to investigate its practical use in the field of UV and strong blue light shielding.

The improvement of the color rendering index using convex-dual-layer remote phosphor geometry with YOCl:Eu3+

White-light emitting diodes (WLEDs) are semiconductor light sources whose construction design is usually made up of a single pumping chip and a single light-conversion film of phosphor compound. The outstanding problem of this traditional setting is the inadequate chroma rendering index (CRI). Introducing a cluster of multiple blue chips with more than one phosphor layer is demonstrated to address that flaw of W-LEDs. This package is called the dual-film remote-phosphor multi-chip WLED. As a consequence, both the light brightness and the CRI are improved. However, for the maximum results, the test on the second layer of phosphor has been performed to continually alter the proportions and densities of phosphor within the silicone. The researchers employed a unique hue design to control the white-light light emitting diode (LED) module. When comparing the actual result to the simulated color coordinates under the hue standard of international commission on illumination (CIE) 1931, the highest difference is found to be around 0.0063 for correlated color temperatures (CCT) of 6600 K and 7700 K. Experiments indicate that the setting of multi-chip and dual-phosphorus is the optimal design for supporting CRI quality and luminous intensity.

Stability Enhancement of CsPbBrI2 Glass Powder in PS Film via a Heat-Water Cyclic Treatment for Backlight Display

Nowadays, an all-inorganic metal halide perovskite (CsPbX3, X = Cl, Br, and I) has shown excellent prospects in liquid crystal display (LCD) backlight device applications. However, in order to better meet the market’s development, the stability of CsPbX3 still remains an urgent problem to be solved. Herein, a heat-water cyclic process of CsPbBrI2 glass powder (RGP) designed to improve stability is proposed. Excitingly, the treated RGP shows better optical properties and heat resistance. Moreover, RGP@PS was prepared with high blue light, water, and heat stabilities. It is particularly noteworthy that RGP6@PS was continuously exposed for 268 h at 60 °C and 90% relative humidity in the blue light (447 nm, 880 W/m2) environment with no decrease in brightness. It illustrates that the CsPbX3 films have made an important breakthrough in stabilities. The LCD device based on RGP@CsPbBr3@PS was designed with a wider color gamut (126%) compared with NTSC 1953. This study explores a new strategy to improve the stability of CsPbX3 thin films for LCD light conversion films.