Light Loss Research Articles

Hollow Microcavity Electrode for Enhancing Light Extraction.

Luminous efficiency is a pivotal factor for assessing the performance of optoelectronic devices, wherein light loss caused by diverse factors is harvested and converted into the radiative mode. In this study, we demonstrate a nanoscale vacuum photonic crystal layer (nVPCL) for light extraction enhancement. A corrugated semi-transparent electrode incorporating a periodic hollow-structure array was designed through a simulation that utilizes finite-difference time-domain computational analysis. The corrugated profile, stemming from the periodic hollow structure, was fabricated using laser interference lithography, which allows the precise engineering of various geometrical parameters by controlling the process conditions. The semi-transparent electrode consisted of a 15 nm thick Ag film, which acted as the exit mirror and induced microcavity resonance. When applied to a conventional green organic light-emitting diode (OLED) structure, the optimized nVPCL-integrated device demonstrated a 21.5% enhancement in external quantum efficiency compared to the reference device. Further, the full width at half maximum exhibited a 27.5% reduction compared to that of the reference device, demonstrating improved color purity. This study presents a novel approach by applying a hybrid thin film electrode design to optoelectronic devices to enhance optical efficiency and color purity.

A low-cost open-source imaging platform reveals spatiotemporal insight into leaf elongation and movement.

Plant organs move throughout the diurnal cycle, changing leaf and petiole positions to balance light capture, leaf temperature, and water loss under dynamic environmental conditions. Upward movement of the petiole, called hyponasty, is one of several traits of the shade avoidance syndrome (SAS). SAS traits are elicited upon perception of vegetation shade signals such as far-red light (FR) and improve light capture in dense vegetation. Monitoring plant movement at a high temporal resolution allows studying functionality and molecular regulation of hyponasty. However, high temporal resolution imaging solutions are often very expensive, making this unavailable to many researchers. Here, we present a modular and low-cost imaging set-up, based on small Raspberry Pi computers, that can track leaf movements and elongation growth with high temporal resolution. We also developed an open-source, semi-automated image analysis pipeline. Using this setup we followed responses to FR enrichment, light intensity, and their interactions. Tracking both elongation and the angle of the petiole, lamina, and entire leaf in Arabidopsis (Arabidopsis thaliana) revealed insight into R:FR sensitivities of leaf growth and movement dynamics and the interactions of R:FR with background light intensity. The detailed imaging options of this system allowed us to identify spatially separate bending points for petiole and lamina positioning of the leaf.

Clinical outcomes of Ahmed glaucoma valve implantation in primary open-angle glaucoma and pseudoexfoliative glaucoma.

To investigate the clinical outcomes of Ahmed glaucoma valve (AGV) implantation in primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG). The patients who underwent AGV implantation for POAG and PEXG between January 2015 and December 2021 in a single tertiary center eye clinic were reviewed retrospectively. Thirty-one eyes with the diagnosis of POAG constituted Group 1 and 40 eyes with the diagnosis of PEXG constituted Group 2. The primary outcome measures were intraocular pressure (IOP) changes after AGV implantation and surgical success at the last visit. We evaluated complete and qualified surgical success using the following three criteria: (1) IOP ≤ 21mmH g, (2) IOP ≤ 18mmHg, and (3) IOP ≤ 15mmHg, as well as the absence of any serious complications, such as light perception loss and phthisis bulbi, and additional de novo glaucoma surgery. The mean follow-up times were 25.2 (± 21.4) months and 27.6 (± 19.8) months for Groups 1 and 2, respectively (p > 0.05). In Groups 1 and 2, the mean preoperative IOPs were 31.9 ± 9.4mmHg and 32.3 ± 8.4mmHg, respectively, which significantly reduced to 14.5 ± 0.7mmHg and 11.6 ± 0.6mmHg, respectively at the last postoperative visit (p < 0.001 for both). The mean IOP value at the last visit was statistically significantly lower in Group 2 (p = 0.006). At the last visit, the number of eyes with qualified success according to criteria 1, 2, and 3 was 26 (83.9%), 25 (80.6%), and 18 (58.1%), respectively, in Group 1 and 39 (97.5%), 39 (97.5%), and 32 (80%), respectively, in Group 2. The comparison of the qualified success rates showed statistically significantly higher rates in Group 2 for criterion 2 (p = 0.038). AGV implantation had high success rates in both POAG and PEXG, but at the final visit, lower IOP levels were reached in the latter.

Zero crossing detection algorithm based on an MLP neural network for differential confocal microscopy

Differential confocal microscopy is widely used because of its ultra-high axial resolution. The surface gradient results in light loss, which decreases the slope of the differential response signal at zero crossing. At this point, when the signal-to-noise ratio is fixed, the traditional linear fitting method to determine the position of zero crossing is subject to significant error influence. To solve these issues, this paper proposes a zero crossing detection algorithm based on a multilayer perceptron (MLP) neural network. Experimental results reveal that the proposed algorithm is more robust and capable of better zero crossing extraction. When numerical aperture (NA)=0.4, the average error is 16.9 nm, which is 55.4 % higher than that of the traditional linear fitting algorithm. The proposed algorithm has a high potential for use with the differential confocal sensor to measure unknown steep surfaces.

Research on field optimization model of heliostat based on ray tracing

In this paper, the average optical efficiency and output power of the tower solar thermal power station are studied. The ray tracing method is used especially to the calculation process and details of the shadow blocking efficiency and collector truncation efficiency are carefully derived. Combined with intelligent optimization algorithm, the key parameters [1][2] of the mirror field layout are optimized. Then, the main method used in this paper is ray tracing. For the calculation of cosine efficiency and shadow blocking efficiency, the coordinate transformation matrix is established in this paper, which simplifies the coordinate calculation. For the calculation of collector truncation efficiency, based on Monte Carlo simulation, and an accurate collector truncation efficiency model is established by random sampling of large samples. Finally, MATLAB software is used to calculate the efficiency of the heliostat in different coordinate positions. The average optical efficiency (62.71%), cosine efficiency (75.65%), shadow blocking efficiency (94.54%), collector truncation efficiency (98.85%), thermal output power (34.77MW), and average annual thermal output power per unit area mirror (0.5535kW/m2) are obtained. This model not only helps to understand the propagation mode of light in the heliostat field, but also can quantitatively evaluate the loss of light.

Effect of skin color on optical properties and the implications for medical optical technologies: a review.

Skin color affects light penetration leading to differences in its absorption and scattering properties. COVID-19 highlighted the importance of understanding of the interaction of light with different skin types, e.g., pulse oximetry (PO) unreliably determined oxygen saturation levels in people from Black and ethnic minority backgrounds. Furthermore, with increased use of other medical wearables using light to provide disease information and photodynamic therapies to treat skin cancers, a thorough understanding of the effect skin color has on light is important for reducing healthcare disparities. The aim of this work is to perform a thorough review on the effect of skin color on optical properties and the implication of variation on optical medical technologies. Published in vivo optical coefficients associated with different skin colors were collated and their effects on optical penetration depth and transport mean free path (TMFP) assessed. Variation among reported values is significant. We show that absorption coefficients for dark skin are to 74% greater than for light skin in the 400 to 1000nm spectrum. Beyond 600nm, the TMFP for light skin is greater than for dark skin. Maximum transmission for all skin types was beyond 940nm in this spectrum. There are significant losses of light with increasing skin depth; in this spectrum, depending upon Fitzpatrick skin type (FST), on average 14% to 18% of light is lost by a depth of 0.1mm compared with 90% to 97% of the remaining light being lost by a depth of 1.93mm. Current published data suggest that at wavelengths beyond 940nm light transmission is greatest for all FSTs. Data beyond 1000nm are minimal and further study is required. It is possible that the amount of light transmitted through skin for all skin colors will converge with increasing wavelength enabling optical medical technologies to become independent of skin color.

Slippery Core‐Sheath Hydrogel Optical Fiber Built by Catalytically Triggered Interface Radical Polymerization

AbstractHydrogel‐based optical waveguides have attracted extensive attention in optogenetics, implantable photomedicine, and biosensors due to their excellent biocompatibility and tissue‐like modulus in compared with traditional SiO2‐based rigid optical fibers. However, the existing ion‐induced supramolecular assembly of alginate‐based hydrogel optical fibers commonly lack of long‐term stability due to poor mechanical property accompanied with swollen. In this paper, a novel catalytic surface polymerization method is developed based on a redox reaction mechanism to in situ grow robust and slippery cladding layer on a core poly(ethylene glycol) dimethacrylate (PEGDA) hydrogel fiber by using the alternative H‐bonding poly(N ‐acryloyl glycinamide) (PNAGA) hydrogels. The resultant hydrogel optical fiber with core‐cladding heterogeneous structure can achieve the desirable total reflection condition, leading to good light transmission and low light loss. The PNAGA cladding with robust H‐bonding network endows the hydrogel optical fiber with high stability and outstanding lubrication in humid environment. More importantly, the hydrogel optical fiber possesses good tissue‐like mechanical performance together with excellent biocompatibility, which shows the great advantages for biomedical applications in compared with traditional glass optical fibers. This work will broaden implantable hydrogel optical fibers in material design and structure processibility, promoting the use of hydrogel‐based optical fibers in various applications.

Theoretical study on radiation effect on threshold of transverse mode instability of Yb-doped fiber amplifiers

&lt;sec&gt;Yb-doped fiber amplifiers and their applications in radiation environments have become more and more attractive in recent years. However, the radiation effect will cause damage to the Yb-doped fibers, which can give negative effect on the output properties of Yb-doped fiber amplifiers. In this work, the influence of radiation effect on the transverse mode instability (TMI) of Yb-doped fiber amplifier is studied. TMI can couple the single light from the fundamental mode to high-order mode, thereby degenerating the beam quality of fiber amplifier. TMI is considered a key limitation of power up-scaling of fiber amplifiers.&lt;/sec&gt;&lt;sec&gt;In this work, the radiation effect on the TMI is studied theoretically, and a formula of TMI threshold is presented by taking the radiation-induced attenuation (RIA), the most important radiation effect for the TMI, into account. The formula is deduced by introducing the loss of signal light induced by RIA into the formerly reported TMI-threshold formula which can be obtained by the linear stability analysis of the numerical model studying the TMI. Then, the relationship between the TMI and radiation dose is also given with the help of Power-Law describing the relationship between the RIA and radiation dose.&lt;/sec&gt;&lt;sec&gt;With the formula, the variations of TMI threshold with the radiation dose and RIA are studied. It is found, as expected, that the TMI threshold decreases monotonically with the increase of RIA or radiation dose. Nevertheless, it is unexpectedly found that, to some extent, the gain coefficient of fiber amplifiers will also affect the radiation effect on TMI threshold. The results reveal that the increase of gain coefficient will lower the sensitivity of TMI threshold to the radiation dose. However, it is also implied that the gain coefficient cannot be too large because it can also make the TMI threshold lowered. Therefore, in order to maintain a high TMI threshold in a radiation environment, sufficient radiation resistance of Yb-doped fiber is essential.&lt;/sec&gt;&lt;sec&gt;Because the RIA can affect not only the TMI threshold but also the output power or efficiency of Yb-doped fiber amplifier, the comparison between two effects of RIA is also discussed. It is found that the threshold of TMI is more sensitive to the radiation than to the output power or efficiency (see the figure attached below), which means that the TMI can exist in the irradiated Yb-doped fiber amplifier, although the output power is reduced because of RIA. This result can be verified by the experimental observation reported formerly. As a result, TMI can become a key limitation to the output power of Yb-doped fiber amplifier in radiation environments. The relevant results can provide significant guidance for the applications of Yb-doped fiber amplifiers in radiation environments.&lt;/sec&gt;

Analysis of Changes in Variation of Neutrophil and Monocyte Parameters, Including Volume, Conductivity and Scatter in Sepsis Patients and Healthy Controls: A Cross-sectional Study

Introduction: Sepsis continues to be a leading cause of mortality and prolonged hospitalisation. The conventional method of blood culture, while considered the gold standard, has limitations such as contamination and delayed reporting. The examination of peripheral smears has uncovered signs suggestive of septicaemia; however, these findings suffer from inter-observer variability and reliance on staining quality. Aim: To investigate the variation of neutrophil and monocyte parameters, including Volume, Conductivity, and Scatter (VCS), in sepsis compared to healthy controls. Materials and Methods: A cross-sectional analytical study was conducted at the Himalayan Institute of Medical Sciences, Swami Rama Himalayan University in Dehradun, Uttarakhand, over the course of one year, from January 2021 to December 2021, involving patients over 18 years of age categorised into sepsis group based on clinical suspicion, sepsis screen, blood culture, and Sequential Organ Failure Assessment (SOFA) score (n=117). A group of healthy controls was also included (n=140). Haematological investigations were performed using the DXH 800 Haematology Analyser (Beckman Coulter, CA, USA) with VCS Technology. Categorical variables were analysed using the Chi-square test, while non parametric data was compared using the Mann-Whitney U test. Results: The average age in the sepsis group was 50.17±13.17 years, while in the control group, it was 38.14±8.78 years. The results revealed higher White Blood Cell (WBC) counts (16.76±7.39)×103 / cumm in the sepsis group compared to healthy controls (6.68±1.42)×103 , absolute neutrophil counts (13.74±7.280)×103 in sepsis patients, and eosinopenia in the sepsis group (0.0114±0.0104)×103 compared to controls (0.23±0.116)×103 . Moreover, mean neutrophilic volumes (158.00±14.840) and monocytic volumes (182.58±18.64) were higher in the sepsis group, while they were lower in healthy controls, which were (149.52±5.23 and 171.17±6.28), respectively. Axial light loss for neutrophil and monocyte was 142.40±11.78 and 121.50±17.93, respectively, while it was lower in healthy controls showing a value of 135.51±7.63 and 119.45±8.25, respectively. Furthermore, mean neutrophilic and monocytic conductivity and scatter were decreased in sepsis. The observed higher WBC counts and absolute neutrophil counts in sepsis patients suggest a premature release of neutrophils from the bone marrow. The alterations in cell volume reflect an immune response. Additionally, the overall scatter of neutrophils and monocytes was reduced, accompanied by increased cellular transparency. Conclusion: The present study contributes valuable insights into the pathophysiological mechanisms underlying sepsis, emphasising the dynamic interplay between immune cells and their functional characteristics. Understanding these variations in cellular parameters could potentially aid in the development of more targeted diagnostic and therapeutic approaches for sepsis, ultimately improving patient outcomes. Further research is warranted to delve deeper into the specific mechanisms driving these observed changes and to explore their clinical implications in the context of sepsis management.

Exploring the fluorescence action spectrum of photosynthesis

The mathematical study of the fluorescence action spectrum of photosynthesis was performed. The calculation of typical spectra for photosynthesis was done for the red and blue frequencies. The transition of the action spectrum of photosynthesis from wavelengths to the frequency scale was completed. A numerical method based on the use of the inverse Fourier transform approach was used to obtain a relaxation curve for the impulse (time) characteristic of fluorescence. It turned out that the radius vector of the module of impulse response in polar coordinates makes one half-turn or half of the period of light oscillations in time. It was established that the optical medium of a plant during the relaxation time has a negative space charge of electrons, inverse properties and properties of the coherent radiation. The condition of neutrality of the material environment is not met. It was found that the ratio of the variable chlorophyll fluorescence for red and blue light has almost the same value. An analysis of the dependence of the quality factor of the chlorophyll spectrum on frequency shows that the fluorescence energy loss in blue light significantly exceeds the energy loss in red light. The proposed method can be used for express analysis of the intensity of photosynthesis. It was also concluded that plants can emit ultra-wideband signals. The relaxation time of chlorophyll fluorescence is shorter than the relaxation time of electronic polarization in atoms (molecules). As a result, a population inversion is created in the optical medium of chlorophyll - there are more atoms in the upper energy level than in the lower level. Due to this, stimulated emission and amplification of light of the radiative recombination occur. In this case, the emission of fluorescence light becomes coherent. All these properties of plants are considered for the first time and have not been described either in domestic or in foreign articles.

Optimizing the design of highly linearly polarized white LED with multilayer metal-dielectric grating structure

In order to emit a linearly polarized light and reduce energy loss for a white light emitting diode (LED), a multilayer metal-dielectric grating structure using GaN-based blue LED is proposed. This multilayer structure is composed of three major functional layers: a fluorescent ceramics layer, a dielectric anti-reflection layer and a linear polarization grating layer. Fluorescent ceramics layer is integrated on the top of GaN-based blue LED, to achieve white light emission. In turn, a dielectric anti-reflection layer and a linear polarization grating layer are also integrated to obtain a higher transmission of white light and improve the conversion efficiency of linear polarization. The structural parameters of each functional layer, including period (150 nm), duty cycle (0.5), height of metal-dielectric grating (55 nm and 80 nm) and thickness of dielectric layer (15 nm), are simulated and optimized by finite-difference time-domain method. Then the multilayer structure is fabricated by UV nanoimprint and its transmission and polarization characteristics are tested. The results show that the transmittance and extinction ratio are higher than 50% and 33.8 dB in the wavelength range of 400–800 nm, and the maximum value can reach 91.3% and 41.3 dB, respectively. It is well verified by experiments that the proposed structure has a steady polarization performance of TM mode in the range of ±20°, which provides a fundamental guarantee for developing the potential applications of polarized white LED.

Accurate color characterization of solar photovoltaic modules for building integration

Accurate and reproducible color characterization is essential for colored building integrated photovoltaic products, both for manufacturing quality control and assessing long-term color stability. However, existing characterization techniques struggle to accurately determine color when a surface is behind a transparent layer like a solar PV laminate. In this study, we compare different colorimetric techniques and propose an innovative colorimeter based on a fiber optic spectrometer and large area illumination to address this issue. Samples with varying transparent glass thicknesses and underlying colors are laminated and characterized using a scanner, an integrated sphere spectrometer, a commercial portable colorimeter, and the proposed large area illumination colorimeter. Results show that common scanners produce darker images and inaccurate color determination due to light losses in the glass. As glass thickness increases, reflectance decreases with the integrated sphere spectrometer and portable colorimeter. However, the large area illumination colorimeter exhibits only minimal signal reduction. High reflective foils experience more reflectance reduction with thicker glass than low reflective ones. All devices yield comparable results without the glass layer. The large area illumination colorimeter, compensating for light losses, proves to be a suitable solution for accurately measuring color under glass laminates using reflected light. For example, it reduces the color change from 57 (commercial portable colorimeter) to only 3 for an ivory colored glass laminate. This innovative tool has the potential to improve color characterization in building integrated photovoltaic products, enabling better manufacturing quality control and assessment of long-term color stability.

Initial Investigation of a Grating Stimulus as a Visual Endpoint for Human Centrifuge Research.

INTRODUCTION: G tolerance has been widely assessed using Peripheral Light Loss (PLL), but this approach has several limitations and may lack sensitivity. The aim of this study was to investigate the use of a foveal visual endpoint for centrifuge research (Grating Loss; GL) and assess its repeatability, reliability, and usability with PLL as a reference.METHODS: A total of 11 subjects undertook centrifuge assessment. Gradual onset sessions (GOR; 0.1 G · s-1) measured both endpoints simultaneously and were performed twice, consisting of six determinations with anti-G suits activated (GOR-On) and six without (GOR-Off). Four determinations of each endpoint were also taken during rapid onset runs (ROR; 3 G · s-1). Usability was scored subjectively.RESULTS: The GL endpoint was reached 0.3-0.5 Gz lower than PLL with each endpoint correlating strongly in GOR-Off (r = 0.93), GOR-On (r = 0.95), and ROR (r = 0.86). The GL had excellent test-retest repeatability (intraclass correlation coefficient: GOR-Off/On = 0.99, ROR = 0.92) and low within-subject variability. Between-subject variance equaled PLL in all conditions. Subjective usability endpoint ratings were equal for all conditions.DISCUSSION: For the 11 individuals tested, the GL was a reliable, repeatable, and usable endpoint, with similar performance to PLL. GL may prove useful as a supplementary endpoint for human centrifuge research as a secondary data point or to reduce fatigue in repeated measurements. The foveal GL stimulus was lost before PLL, contrary to popular models of visual changes under +Gz.Britton J, Connolly DM, Hawarden DE, Stevenson AT, Harridge SDR, Green NDC, Pollock RD. Initial investigation of a grating stimulus as a visual endpoint for human centrifuge research. Aerosp Med Hum Perform. 2023; 94(12):894-901.

Structural optimization and performance testing of concentrated photovoltaic panels for pavement

Solar pavement can convert sunlight shining on the pavement surface into clean electricity through photovoltaic panels, thereby transforming the energy structure of road transportation. In order to balance the light transmittance and anti-skid resistance of the solar pavement surface, this study proposed a concentrated photovoltaic panel (CPP) structure for pavement. The panel structure was optimized, and a laboratory model was developed. The mechanical properties and durability of the panel were tested by the multi-functional material test system (MTS) and the model mobile load simulator 3 (MMLS3). Furthermore, the electrical performance was evaluated by an outdoor test, followed by an economic evaluation. The results show that the optimal structural dimensions of the CPP for pavement are 540 mm long × 540 mm in length × 144.62 mm in thickness. The maximum flexural tensile strength of its anti-skid concentrated panel is 61.67 MPa, satisfying the requirements of the traffic load. After 1.35 million cycles of loading, the surface of the anti-skid concentrated panel is free of cracks and deformation and has no obvious wear, exhibiting good transmittance durability and excellent wear resistance. In addition, the overall structure of the panel counteracts the light loss effect of the material and improves the light concentration performance, providing a gain effect on the power generation of the panel, especially in the case of high irradiance. The return on investment (ROI) of CPP for pavement is 54.42%, with cost recovery in 9.87 years. The levelized cost of energy is 0.67 CNY/kWh, indicating significant economic benefits. At the same time, 1539.3 kg/m2 of CO2 emissions can be avoided during the operation cycle, and the environmental benefits are also considerable. This study can provide a reference for the promotion and application of photovoltaic power generation technology in road engineering.

Low-Cost Angle Sensor for Robotics Applications Using Plastic Optical Fiber Based on Optical Loss Mechanism.

Robotic systems and the human body consist of numerous joint structures, all of which require precise angle adjustments. At present, encoder, strain gauge, and electrical resistance-based sensors are commonly used for angle measurement. However, these sensors have limitations when used in underwater or in environments with strong electromagnetic waves. Therefore, we have developed an angle sensor based on step-index profile plastic optical fiber (SI-POF), which is cost-effective and highly durable, in this study in order to overcome the limitations of existing angle measurement sensors. To this end, the amount of light loss according to the gab and angle changes that occur when the POF angle sensor is applied to the robot arm was experimentally measured, and based on the results, a simulation of the amount of light loss when the two losses occurred at the same time was conducted. In addition, the performance of the POF angle sensor was evaluated by measuring sensitivity and resolution, and comparative verification with a commonly used encoder was conducted to verify the reliability of sensors in extreme environments, such as those with electromagnetic fields and those that are underwater. Through this, the reliability and practicality of the POF angle sensor were confirmed. The results obtained in this study suggest that POF-based angle sensors can contribute to the development of the biomimetic robot industry as well as ordinary robots, especially in environments where existing sensors are difficult to apply, such as areas with underwater or electromagnetic interference (EMI).

Hexagonal mesoporous silica/perovskite oxides composites as unique scattering layers in photoelectrodes of high performance dye-sensitized photovoltaics

As the photoactive TiO2 film in dye-sensitized solar cells (DSSCs) is transparent to incident light owing to its nano-sized particles, the efficiency may be affected by the light loss. Therefore, light scattering layers including CeMnO3, CeFeO3, CeSnO3, CeZnO3, 3D-hexagonal mesoporous silica (HMS-3), and HMS-3:CeMnO3 composites were deposited on TiO2 layer by doctor blade technique in order to harvest more sunlight. To characterize each material, XRD, FTIR, PL, DRS, FESEM, EDS, and BET analyses were investigated. In addition, dye absorption capacity, power conversion efficiency (PCE), open-circuit voltage decay (OCVD), and charge transfer parameters were assessed. According to photovoltaic data, TiO2/50 wt% HMS-3+50 wt% CeMnO3 based DSSC brought about the maximum PCE of 7.47% with fill factor (FF), short-circuit current density (Jsc), and open-circuit voltage (Voc) of 0.48, 21.17 mA/cm2, and 0.738 V, respectively, displaying 75.4% higher PCE compared to solar cell fabricated by TiO2 (PCE = 4.26%, Jsc = 11.72, Voc = 0.685 V, FF = 0.53). The champion 50 wt% HMS-3+50 wt% CeMnO3 composite featured large particles with high porosity, which could enhance light scattering and cause the light path to be longer, based on the Mie theory. Moreover, because of the big surface area (643.80 m2/g), large pore volume (0.4282 cm3/g), and appropriate N719 dye loading of the champion 50 wt% HMS-3+50 wt% CeMnO3 composite, more dye molecules were excited, and the number of light-generated electrons was boosted, elevating the current density, facilitating faster charge transfer from the TiO2 photoanode towards the Pt electrode, and limiting electron-hole recombination to a high extent, which led to an enormous improvement in efficiency.

Reduction of light output of plastic scintillator tiles during irradiation at cold temperatures and in low-oxygen environments

The advent of the silicon photomultiplier has allowed the development of highly segmented calorimeters using plastic scintillator as the active media, with photodetectors embedded in the calorimeter, in dimples in the plastic. To reduce the photodetector’s dark current and radiation damage, the high granularity calorimeter designed for the high luminosity upgrade of the CMS detector at CERN’s Large Hadron Collider will be operated at a temperature of about −30 °C. Due to flammability considerations, a low oxygen environment is being considered. However, the radiation damage to the plastic scintillator during irradiation in this operating environment needs to be considered. In this paper, we present measurements of the relative decrease of light output during irradiation of small plastic scintillator tiles read out by silicon photomultipliers. The irradiations were performed using a 60Co source both to produce the tiles’ light and as a source of ionizing irradiation at dose rates of 0.3, 1.3, and 1.6 Gy/h, temperatures of −30, −15, −5, and 0 °C, and with several different oxygen concentrations in the surrounding atmosphere. The effect of the material used to wrap the tile was also studied. Substantial temporary damage, which annealed when the sample was warmed, was seen during the low-temperature irradiations, regardless of the oxygen concentration and wrapping material. The relative light loss was largest with 3MTM Enhanced Specular Reflector Film wrapping and smallest with no wrapping, although due to the substantially higher light yield with wrapping, the final light output is largest with wrapping. The light loss was less at warmer temperatures. Damage with 3% oxygen was similar to that in standard atmosphere. Evidence of a plateau in the radical density was seen for the 0 °C data.

Effect of Co-Doping on the Photoelectric Properties of the Novel Two-Dimensional Material Borophene

Borophene is a novel two-dimensional material with abundant crystal structure and photoelectric properties. We focus on the effect of co-doping on the electronic structure and optical properties of borophene using the first-principles method. The results show that the structure of Al and Ga co-doped borophene is obviously distorted because Al and Ga atoms have formed bonds with a bond length of 2.378 Å, and the two B atoms that bond together with Al and Ga are no longer formed bonds. However, it is also a two-dimensional planar structure after co-doping. After co-doping, the band gap width of the borophene system is narrowed from 1.409 eV to 1.376 eV, and the band gap is narrowed by 0.033 eV. Mulliken population analysis shows an obvious charge transfer between Al-B and Ga-B atoms in the co-doped borophene. The calculation of optical properties shows that the static dielectric constant ε1 (0) increases from 5.08 to 7.01, and ε2 (ω) is larger than that of the undoped sample in the low-energy range. Thus, the co-doping of Al and Ga can enhance the electromagnetic energy storage capacity and the visible light absorption ability. Although the reflectance of borophene is reduced by co-doping (the peak of the reflectivity can be decreased from 71% to 61% at E = 2.94 eV), it still presents metallic reflection characteristics. The static refractive index n0 can be increased from 2.25 to 2.65 by co-doping. The extinction coefficient shows strong band edge absorption at the low-energy range with an absorption edge of 0.85 eV. The light loss is limited to a very narrow energy range of approximately 7.30 eV, which indicates that borophene co-doped with Al and Ga can also be used as a light storage material. The optical conductivity reaches its maximum at E = 1.78 eV and 2.52 eV, which correspond to the light irradiation with a wavelength of 698 nm (red light) and 492 nm (cyan light), respectively. The results show that the Al-Ga co-doped borophene is sensitive to cyan light and red light, so it can be used to make photosensitive devices. The results can hopefully fill the gap in the application of borophene in semiconductor photoelectric devices and provide a theoretical basis for its application.

Preparation of NaYF4:Tm, Yb, and Gd Luminescent Nanorods/SiO2 Nanospheres Composite Thin Film and Its Application in Perovskite Solar Cells.

In this study, we aim to minimize light loss and achieve high power conversion efficiencies (PCE) in perovskite solar cells (PSCs) by employing a spectral conversion film component with antireflection properties. In our scheme, NaYF4:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films are applied on CH3NH3PbI3 PSCs to improve the device efficiency. The film was fabricated by spin coating an aged silica sol containing NaYF4:Tm, Yb, and Gd luminescent nanorods. The size and the spectral conversion properties of the NaYF4:Tm, Yb, and Gd luminescent nanorods were controlled by tuning the Gd3+ ion concentration. The microstructure and the transmittance properties of the thin film were controlled by changing the concentration of NaYF4:Tm, Yb, and Gd luminescent nanorod in silica sol. The thin films have excellent spectral conversion properties while exhibiting a maximum transmittance. The photovoltaic performance of PSCs with NaYF4:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films was systematically investigated. The light transmittance was optimized to 95.1% on a cleaned glass substrate, which resulted in an average increase of about 3.0% across the broadband range of 400-800 nm. The optimized films widen the spectrum of light absorbed by conventional PSC cells and reduce reflections across a broad range, enhancing the photovoltaic performance of PSCs. As a result, the PCE of the PSC increased from 14.51% for the reference device without a thin film to 15.67% for the PSC device with an optimized thin film. This study presents a comprehensive solution to the problem of Fresnel reflection and spectral response mismatch of the PSCs, which provides new ideas for the light management of PSCs.

Scintillation and radioluminescence mechanism in β-Ga2O3 semiconducting single crystals

In this paper, we present the results of experiments on samples of β-Ga2O3 single crystals under a project aimed at assessing and improving the scintillation performance of this material by studying scintillation and radioluminescence mechanism and its limitations. In addition to standard experiments, such as scintillation light yields and time profiles, radio-, and thermoluminescence, we developed and tested a new and promising two-beam experiment, in which a sample is excited by an X-ray beam and additionally stimulated by an IR laser diode.Fe and Mg doping compensate for the inherent n-type conductivity of β-Ga2O3 to obtain semi-insulating single crystals for large-area substrates and wafers. At the same time, residual Fe and Ir are ubiquitous uncontrolled impurities leached from the Ir crucibles used to grow large bulk crystals by the Czochralski method.For these experiments, we selected four samples cut from the Czochralski grown 2-cm diameter β-Ga2O3 single crystal boules; one with a reduced Fe content, two unintentionally Fe- and Ir-doped (UID) with lower and higher Fe content, and one doped with Mg.We find that steady-state radioluminescence spectra measured at temperatures between 10 and 350 K are dominated by the UV emission peaking at about 350–370 nm. Unfortunately, even for the best sample with a reduced Fe-content, the intensity of this emission drops precipitously with the temperature down to about 10 % at 300 K.From the two-beam experiments, we conclude that recombination via inadvertent Fe impurity involving three charge states (2+, 3+, and 4+) may reduce a steady-state UV emission of β-Ga2O3 under X-ray excitation by as much as 60–70 %, one-third to one-half of which is due to the recombination (specific for Fe-doped β-Ga2O3) involving the 4+ and 3+ charge states of Fe and the remaining 50–70 % being due to a more familiar route typical of other oxides, involving the 2+ and 3+ charge states of Fe. These losses are at higher temperatures enhanced by a thermally activated redistribution of self-trapped holes (STHs). In addition, the trapping of electrons by Fe and holes by Mg, Fe, and Ir may be responsible for scintillation light loss and reduction of the zero-time amplitude essential for the fast timing scintillation applications.Despite indirect evidence of competitive recombination in β-Ga2O3 involving a deep Ir3+/4+ donor level, we could not quantitatively assess losses of the UV steady state radioluminescence light due to the inadvertent Ir impurity.