Search Results (32)

The development of ultrahigh-concentration photovoltaic (UHCPV) systems plays a pivotal role in advancing sustainable solar energy technologies. As the demand for clean energy grows, the need to align concentrated photovoltaic (CPV) system design with high-efficiency solar cell production becomes critical for maximizing energy yield while minimizing resource use. Despite some experimental efforts in UHCPV development, there remains a gap in integrating Fresnel lens-based systems with the comprehensive thermal modeling of key components in improving system sustainability and performance. To bridge this gap and promote more energy-efficient designs, a detailed numerical model was established to evaluate both the thermal and optical performance of a UHCPV system. This model contributes to the sustainable design process by enabling informed decisions on system efficiency, thermal management, and material optimization before physical prototyping. Through COMSOL Multiphysics simulations, the system was assessed under direct normal irradiance (DNI) ranging from 400 to 1000 W/m². Optical simulations indicated a high theoretical optical efficiency of ~93% and a concentration ratio of 1361 suns, underscoring the system’s potential to deliver high solar energy conversion with minimal land and material footprint. Moreover, the integration of thermal and optical modeling ensures a holistic understanding of system behavior under varying ambient temperatures (20–50 °C) and convective cooling conditions (heat transfer coefficients between 4 and 22 W/m².K). The results showed that critical optical components remain within safe temperature thresholds (<54 °C), while the receiver stage operates between 78.5 °C and 157.4 °C. These findings highlight the necessity of an effective cooling mechanism—not only to preserve system longevity and safety but also to maintain high conversion efficiency, thereby supporting the broader goals of sustainable and reliable solar energy generation. Full article

This study addresses the development and optothermal analysis of donor–acceptor thin layers, including materials universally used in organic photovoltaic cells. This article presents the impact of temperature on the optical properties and morphology of thin films made from materials commonly used in organic solar cells. This research focused on two donor materials (PTB7 and PTB7th) and two non-fullerene acceptors (Y5 and Y6), individually and in binary combinations with PTB7 and PTB7th. This study employed various techniques, including UV–Vis spectroscopy, ellipsometry, and atomic force microscopy (AFM), to analyze changes in the absorption, refractive index, extinction coefficient, and morphology at temperatures ranging from 30 °C to 120 °C. This research shows reversible changes in thickness and absorption with temperature, but the extent of these changes differs between PTB7 and PTB7th. Y5 shows some reversible changes, while Y6 demonstrates greater instability and more permanent changes at higher temperatures. The enhanced thermal stability of binary mixtures compared to single-component materials was observed. Full article

Photonic integrated circuits (PICs) are crucial for advanced applications in telecommunications, quantum computing, and biomedical fields. Silicon nitride (SiN)-based platforms are promising for PICs due to their transparency, low optical loss, and thermal stability. However, achieving efficient thermo-optic (TO) modulation on SiN remains challenging due to limited reconfigurability and high power requirements. This study aims to optimize TO phase shifters on SiN platforms to enhance power efficiency, reduce device footprint, and minimize insertion losses. We introduce a CMOS-compatible plasmo-photonic TO phase shifter using a SiOC material layer with a high TO coefficient combined with aluminum heaters on a SiN platform. We evaluate four interferometer architectures—symmetric and asymmetric Mach–Zehnder Interferometers (MZIs), an MZI with a ring resonator, and a single-arm design—through opto-thermal simulations to refine performance across power, losses, footprint, and switching speed metrics. The asymmetric MZI with ring resonator (A-MZI-RR) architecture demonstrated superior performance, with minimal power consumption (1.6 mW), low insertion loss (2.8 dB), and reduced length (14.4 μm), showing a favorable figure of merit compared to existing solutions. The optimized SiN-based TO switches show enhanced efficiency and compactness, supporting their potential for scalable, energy-efficient PICs suited to high-performance photonic applications. Full article

When the size of the molybdenum disulfide (MoS₂) is reduced to a few nanometers, a distinctive photoluminescence is observed due to the strong effect of quantum confinement. In this study, we fabricated MoS₂ quantum dots (QDs) using a simple and green process. We dissolved the powder of MoS₂ in various solvents, including N-Methyl-2-pyrrolidone (NMP), ethanol (EtOH), and deionized water (DIW), and dispersed it by sonication or solvent-thermal exfoliation. The synthesized MoS₂ QDs were characterized for their optical properties. Transmission electron microscopy (TEM) was used to analyze the particle size and morphology; UV-visible spectrometer and photoluminescence tests were employed to measure optical absorption, bandgaps, and optical emission. The photothermal test was designed for the evaluation of the optothermal conversion. In vitro cultures of 3T3 fibroblast cells were evaluated for the biocompatibility of the MoS₂ QDs. Results from different experiments were cross-examined and analyzed to understand the relation among different syntheses, microstructures, and optical properties of MoS₂ QDs. A yield of 15% MoS₂ QDs was obtained when synthesized in ethanol by thermal exfoliation. They also showed satisfactory optothermal effects. Full article

Photothermal techniques are infrared remote sensing techniques that have been used for biomedical applications, as well as industrial non-destructive testing (NDT). Machine learning is a branch of artificial intelligence, which includes a set of algorithms for learning from past data and analyzing new data, without being explicitly programmed to do so. In this paper, we first review the latest development of machine learning and its applications in photothermal techniques. Next, we present our latest work on machine learning for data analysis in opto-thermal transient emission radiometry (OTTER), which is a type of photothermal technique that has been extensively used in skin hydration, skin hydration depth profiles, skin pigments, as well as topically applied substances and skin penetration measurements. We have investigated different algorithms, such as random forest regression, gradient boosting regression, support vector machine (SVM) regression, and partial least squares regression, as well as deep learning neural network regression. We first introduce the theoretical background, then illustrate its applications with experimental results. Full article

A 3D manipulation technique based on two optothermally generated and actuated surface-bubble robots is proposed. A single laser beam can be divided into two parallel beams and used for the generation and motion control of twin bubbles. The movement and spacing control of the lasers and bubbles can be varied directly and rapidly. Both 2D and 3D operations of micromodules were carried out successfully using twin bubble robots. The cooperative manipulation of twin bubble robots is superior to that of a single robot in terms of stability, speed, and efficiency. The operational technique proposed in this study is expected to play an important role in tissue engineering, drug screening, and other fields. Full article

Photoluminescent (PL) layers and electroluminescent (EL) systems have gained significant attention for their applications in constructing flat panels, screen monitors, and lighting systems. In this study, we present a groundbreaking approach to fabricating temperature sensors using barium-calcium zirconium titanate (BCZT) with thermo-optic properties, leading to the development of opto-thermal sensors for electric vehicle battery packs. We prepared zinc sulfide (ZnS) fluorescent films on BCZT ceramics, specifically two optimal compositions, BCZT0.85 (Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃) and BCZT0.9 (Ba_0.9Ca_0.1Zr_0.1Ti_0.9O₃), via the solid-state reaction method for the dielectric layer. The BCZT powders were calcined at varying temperatures (1200 and 1250 °C) and dwell times (2 and 4 h). The resulting phase formation and microstructure characteristics were analyzed using X-ray diffraction and scanning electron microscopy, respectively. Our investigation aimed to establish a correlation between the dielectric behavior and optical properties to determine the optimal composition and conditions for utilizing BCZT as thermal detectors in electric vehicle battery packs. All BCZT powders exhibited a tetragonal phase, as confirmed by JCPDS No. 01-079-2265. We observed an increase in the dielectric constant with higher calcining temperatures or longer dwell times. Remarkably, BCZT0.85 ceramic sintered at 1250 °C for 4 h displayed the highest dielectric constant of 15,342, establishing this condition as optimal for preparing the dielectric film with a maximum dielectric constant of 42. Furthermore, we investigated the temperature-dependent electroluminescence intensity of the samples, revealing a significant enhancement with increasing temperature, reaching its peak at 80 °C. Additionally, we observed a positive correlation between electroluminescence intensity and dielectric constant, indicating the potential for improved opto-thermal sensors. The findings from this study offer promising opportunities for the development of advanced opto-thermal sensors with potential applications in electric vehicle battery packs. Our work contributes to the expanding field of photoluminescent and electroluminescent systems by providing novel insights into the design and optimization of efficient and reliable sensors for thermal monitoring in electric vehicle technologies. Full article

The applications of three-dimensional materials combined with two-dimensional materials are attractive for constructing high-performance electronic and photoelectronic devices because of their remarkable electronic and optical properties. However, traditional preparation methods usually involve mechanical transfer, which has a complicated process and cannot avoid contamination. In this work, chemical vapor deposition was proposed to vertically synthesize self-assembly oriented hexagonal boron nitride on gallium nitride directly. The material composition, crystalline quality and orientation were investigated using multiple characterization methods. Thermal conductivity was found to be enhanced twofold in the h-BN incorporated sample by using the optothermal Raman technique. A vertical-ordered (VO)h-BN/GaN heterojunction photodetector was produced based on the synthesis. The photodetector exhibited a high ultraviolet photoresponsivity of up to 1970.7 mA/W, and detectivity up to 2.6 × 10¹³ Jones, and was stable in harsh high temperature conditions. Our work provides a new synthesis method to prepare h-BN on GaN-based materials directly, and a novel vertically oriented structure of VO-h-BN/GaN heterojunction, which has great application potential in optoelectronic devices. Full article

The weak absorption of a laser beam generates in a fluid an inhomogeneous refractive index profile acting as a negative lens. This self-effect on beam propagation, known as Thermal Lensing (TL), is extensively exploited in sensitive spectroscopic techniques, and in several all-optical methods for the assessment of thermo-optical properties of simple and complex fluids. Using the Lorentz–Lorenz equation, we show that the TL signal is directly proportional to the sample thermal expansivity $\alpha$, a feature allowing minute density changes to be detected with high sensitivity in a tiny sample volume, using a simple optical scheme. We took advantage of this key result to investigate the compaction of PniPAM microgels occurring around their volume phase transition temperature, and the temperature-driven formation of poloxamer micelles. For both these different kinds of structural transitions, we observed a significant peak in the solute contribution to $\alpha$, indicating a decrease in the overall solution density—rather counterintuitive evidence that can nevertheless be attributed to the dehydration of the polymer chains. Finally, we compare the novel method we propose with other techniques currently used to obtain specific volume changes. Full article

Pursuing novel materials with efficient photothermal conversion under irradiation at the near-infrared region windows (NIR, 750–850 nm; NIR-I and NIR-II, 1000–1320 nm)) is of great importance due to their irreplaceable applications, especially in the biomedical field. Herein, on the basis of a coordination chemistry strategy, an iron-based metal-organic framework (MOF) of [N(CH₃)₄]₂[Fe₃(NDC)₄]·DMF·3H₂O (Fe-NDC, 1,4-H₂NDC = 1,4-naphthalenedicarboxylic acid, N(CH₃)₄⁺ = tetramethyl-ammonium, and DMF = N,N-dimethylformamide) was prepared and characterized. Due to the d-d transition effect introduced by coordination with the transition-metal ion of iron and the highly conjugated naphthalenic moiety in 1,4-H₂NDC, guaranteeing an energy transfer between iron and the organic module, Fe-NDC shows a remarkable broad absorption, which could be extended into the NIR-II section. As a result, Fe-NDC could be irradiated by NIR laser (both 808 and 1064 nm) to achieve photothermal conversion. This work sets a good example to inspire the future designation of NIR light-irradiated photothermal materials based on the first-row transition metals. Full article

Solar cookers can greatly reduce the overall carbon footprint of the cooking done in India. In the present work a funnel-type solar cooker is designed using cardboard. After making the solar cooker it is then analyzed on the various performance metrics namely the figures of merit, efficiency value and Cooker Opto–thermal Ratio (COR) which are dependent parameters. Paraffin wax which is a phase change material (PCM) is also incorporated in the testing process to evaluate the overall improvement in the thermal efficiency of the solar cooker. The time taken to break is also calculated. The experimental results show that the solar cooker is capable of reaching a temperature of 125 °C. From the results it can also be seen that using paraffin wax also offers significant improvement in the overall thermal efficiency. The results are tested on various parts of India considering the major cities such as Chennai, Trivandrum, Kanpur and Delhi with the ANN model, which is a deep learning model. The advantage of this model is that it can forecast and estimate the temperature of the absorber plate and water from weather forecasting data which is used to calculate F1 and F2 metrics for the performance of the solar cooker. For all the cities, the model’s R2 value is greater than 99% and RMSE values are small. Full article

Past work has focused on the thermal properties of microscale/nanoscale suspended/supported graphene. However, for the thermal design of graphene-based devices, the thermal properties of giant-scale (~mm) graphene, which reflects the effect of grains, must also be investigated and are critical. In this work, the thermal conductivity variation with temperature of giant-scale chemical vapor decomposition (CVD) graphene supported by poly(methyl methacrylate) (PMMA) is characterized using the differential transient electrothermal technique (diff-TET). Compared to the commonly used optothermal Raman technique, diff-TET employs joule heating as the heating source, a situation under which the temperature difference between optical phonons and acoustic phonons is eased. The thermal conductivity of single-layer graphene (SLG) supported by PMMA was measured as 743 ± 167 W/(m·K) and 287 ± 63 W/(m·K) at 296 K and 125 K, respectively. As temperature decreased from 296 K to 275 K, the thermal conductivity of graphene was decreased by 36.5%, which can be partly explained by compressive strain buildup in graphene due to the thermal expansion mismatch. Full article

While junction temperature control is an indispensable part of having reliable solid-state lighting, there is no direct method to measure its quantity. Among various methods, temperature-sensitive optical parameter-based junction temperature measurement techniques have been used in practice. Researchers calibrate different spectral power distribution behaviors to a specific temperature and then use that to predict the junction temperature. White light in white LEDs is composed of blue chip emission and down-converted emission from photoluminescent particles, each with its own behavior at different temperatures. These two emissions can be combined in an unlimited number of ways to produce diverse white colors at different brightness levels. The shape of the spectral power distribution can, in essence, be compressed into a correlated color temperature (CCT). The intensity level of the spectral power distribution can be inferred from the luminous flux as it is the special weighted integration of the spectral power distribution. This paper demonstrates that knowing the color characteristics and power level provide enough information for possible regressor trainings to predict any white LED junction temperature. A database from manufacturer datasheets is utilized to develop four machine learning-based models, viz., k-Nearest Neighbor (KNN), Radius Near Neighbors (RNN), Random Forest (RF), and Extreme Gradient Booster (XGB). The models were used to predict the junction temperatures from a set of dynamic opto-thermal measurements. This study shows that machine learning algorithms can be employed as reliable novel prediction tools for junction temperature estimation, particularly where measuring equipment limitations exist, as in wafer-level probing or phosphor-coated chips. Full article

The optothermal manipulation of micro-objects is significant for understanding and exploring the unknown in the microscale word, which has found many applications in colloidal science and life science. In this work, we study the transverse forces of an optothermal trap in front of a gold film, which is an absorbing reflective surface for the incident laser beam. It is demonstrated that optothermal forces can be divided into two parts: optical force of a standing-wave trap, and thermal force of a thermal trap. The optical force of the standing-wave trap can be obtained by measuring the optical trapping force close to a non-absorbing film with same reflectance. The thermal force can be obtained by subtracting the optical force of the standing-wave trap from the total trapping force of the optothermal trap close to the gold film. The results show that both optical and thermal trapping forces increase with laser power increasing. The optical trapping force is larger than the thermal trapping force, which is composed of convective drag force and thermophoretic force. Further experiment is run to study the composition of thermal force. The result shows that the convective flow is generated later than the thermophoretic flow. The results proposed here are useful for enabling users to optimize optothermal manipulation method for future applications. Full article

Possibility of controlling the temperature of the vein wall during endovasal laser treatment (EVLT) is investigated. The desired medical effect is achieved by the coagulation of the vein wall at the temperature of 80 °C. Heating of the vein wall is mainly due to the efficient conversion of laser radiation into heat in an optothermal fiber converter (OTFC) located at the output end of the optical fiber placed inside the vein. Titanium-containing optothermal fiber converter (TOTFC) is very promising for EVLT application due to its high efficiency in converting laser energy into thermal energy and its smooth shape that excludes perforation of the vein wall when the fiber moves inside the vein. During the endovasal laser treatment heated by laser radiation TOTFC emits an IR signal which can be used for controlling the temperature on the vein wall during endovasal laser treatment. At present study, a computer thermophysical model of the EVLT with TOTFC has been developed in the COMSOL Multiphysics 5.4 program (COMSOL Inc., Burlington, MA, USA). In the EVLT model, a laser radiation wavelength of 980 nm with an average laser power of 8–14 W to the traction speed of the optical fiber in range of 1–7 mm/s is applied. The dependence of the TOTFC temperature and the temperature on the vein wall has been numerically investigated. In accordance with Planck’s formula, the dependence of the spectral luminosity density of a blackbody simulating IR signal from TOTFC on its temperature has been determined. The spectral luminosity density in a wide range the wavelength of 0.4–20 μm, as well as in spectral ranges limited by the transmission of the quartz fiber and the sensitivity of Ge and PbS photodetectors was defined. The possibility of controlling the average power of the laser radiation depending on the magnitude of the change in the spectral luminosity density of TOTFC during EVLT is demonstrated. The results obtained can be useful in developing laser medical equipment and materials for use in vascular surgery at endovasal laser treatment. Full article