Combined nano and micro structuring for enhanced radiative cooling and efficiency of photovoltaic cells

AbstractOutdoor devices comprising materials with mid-IR emissions at the atmospheric window (8–13 μm) achieve passive heat dissipation to outer space (~ − 270 °C), besides the atmosphere, being suitable for cooling applications. Recent studies have shown that the micro-scale photonic patterning of such materials further enhances their spectral emissivity. This approach is crucial, especially for daytime operation, where solar radiation often increases the device heat load. However, micro-scale patterning is often sub-optimal for other wavelengths besides 8–13 μm, limiting the devices’ efficiency. Here, we show that the superposition of properly designed in-plane nano- and micro-scaled periodic patterns results in enhanced device performance in the case of solar cell applications. We apply this idea in scalable, few-micron-thick, and simple single-material (glass) radiative coolers on top of simple-planar Si substrates, where we show an ~ 25.4% solar absorption enhancement, combined with a ~ ≤ 5.8 °C temperature reduction. Utilizing a coupled opto-electro-thermal modeling we evaluate our nano-micro-scale cooler also in the case of selected, highly-efficient Si-based photovoltaic architectures, where we achieve an efficiency enhancement of ~ 3.1%, which is 2.3 times higher compared to common anti-reflection layers, while the operating temperature of the device also decreases. Besides the enhanced performance of our nano-micro-scale cooler, our approach of superimposing double- or multi-periodic gratings is generic and suitable in all cases where the performance of a device depends on its response on more than one frequency bands.

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Short-Pulse Lasers: A Versatile Tool in Creating Novel Nano-/Micro-Structures and Compositional Analysis for Healthcare and Wellbeing Challenges

Nanomaterials ◽

10.3390/nano11030712 ◽

2021 ◽

Vol 11 (3) ◽

pp. 712

Author(s):

Ahmed Al-Kattan ◽

David Grojo ◽

Christophe Drouet ◽

Alexandros Mouskeftaras ◽

Philippe Delaporte ◽

...

Keyword(s):

Laser Ablation ◽

Surface Engineering ◽

Short Pulse ◽

Chemical Properties ◽

Compositional Analysis ◽

Periodic Patterns ◽

Laser Ablation In Liquid ◽

Micro Scale ◽

Direct Laser ◽

Contact Free

Driven by flexibility, precision, repeatability and eco-friendliness, laser-based technologies have attracted great interest to engineer or to analyze materials in various fields including energy, environment, biology and medicine. A major advantage of laser processing relies on the ability to directly structure matter at different scales and to prepare novel materials with unique physical and chemical properties. It is also a contact-free approach that makes it possible to work in inert or reactive liquid or gaseous environment. This leads today to a unique opportunity for designing, fabricating and even analyzing novel complex bio-systems. To illustrate this potential, in this paper, we gather our recent research on four types of laser-based methods relevant for nano-/micro-scale applications. First, we present and discuss pulsed laser ablation in liquid, exploited today for synthetizing ultraclean “bare” nanoparticles attractive for medicine and tissue engineering applications. Second, we discuss robust methods for rapid surface and bulk machining (subtractive manufacturing) at different scales by laser ablation. Among them, the microsphere-assisted laser surface engineering is detailed for its appropriateness to design structured substrates with hierarchically periodic patterns at nano-/micro-scale without chemical treatments. Third, we address the laser-induced forward transfer, a technology based on direct laser printing, to transfer and assemble a multitude of materials (additive structuring), including biological moiety without alteration of functionality. Finally, the fourth method is about chemical analysis: we present the potential of laser-induced breakdown spectroscopy, providing a unique tool for contact-free and space-resolved elemental analysis of organic materials. Overall, we present and discuss the prospect and complementarity of emerging reliable laser technologies, to address challenges in materials’ preparation relevant for the development of innovative multi-scale and multi-material platforms for bio-applications.

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Analysis of Sustainable Materials for Radiative Cooling Potential of Building Surfaces

Sustainability ◽

10.3390/su10093049 ◽

2018 ◽

Vol 10 (9) ◽

pp. 3049 ◽

Cited By ~ 3

Author(s):

Roxana Family ◽

M. Mengüç

Keyword(s):

Heat Transfer ◽

Emission Spectra ◽

Spectral Emissivity ◽

Volumetric Analysis ◽

Solar Heating ◽

Heat Transfer Analysis ◽

Surface Phenomenon ◽

Radiative Cooling ◽

Atmospheric Window ◽

Building Surfaces

The main goal of this paper is to explore the radiative cooling and solar heating potential of several materials for the built environment, based on their spectrally-selective properties. A material for solar heating, should have high spectral emissivity/absorptivity in the solar radiation band (within the wavelength range of 0.2–2 μm), and low emissivity/absorptivity at longer wavelengths. Radiative cooling applications require high spectral emissivity/absorptivity, within the atmospheric window band (8–13 μm), and a low emissivity/absorptivity in other bands. UV-Vis spectrophotometer and FTIR spectroscopy, are used to measure, the spectral absorption/emission spectra of six different types of materials. To evaluate the radiative cooling potential of the samples, the power of cooling is calculated. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis is used. Results are discussed for the selection of the best materials, for different applications on building surfaces.

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Heat Transfer and Its Innovative Applications

Inventions ◽

10.3390/inventions4010004 ◽

2019 ◽

Vol 4 (1) ◽

pp. 4

Author(s):

Ping-Hei Chen ◽

Hyung Cho

Keyword(s):

Heat Transfer ◽

Artificial Intelligence ◽

High Speed ◽

Heat Dissipation ◽

Outer Space ◽

Electronic Devices ◽

Daily Lives ◽

Autonomous Cars

Innovative and high-end techniques have been recently developed in academic institutes and are gradually being employed in our daily lives for improving living quality, namely, artificial intelligence (AI) technology, autonomous cars, hyper-loop for high-speed transportation, miniaturization of electronic devices, heat dissipation from cooling films to outer space, and so on [...]

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Rigorous coupled-wave analysis of absorption enhancement in vertically illuminated silicon photodiodes with photon-trapping hole arrays

Nanophotonics ◽

10.1515/nanoph-2019-0164 ◽

2019 ◽

Vol 8 (10) ◽

pp. 1747-1756 ◽

Cited By ~ 1

Author(s):

Jun Gou ◽

Hilal Cansizoglu ◽

Cesar Bartolo-Perez ◽

Soroush Ghandiparsi ◽

Ahmed S. Mayet ◽

...

Keyword(s):

Absorption Enhancement ◽

Hole Array ◽

Wave Analysis ◽

Si Substrates ◽

Back Reflection ◽

Rigorous Coupled Wave Analysis ◽

Hole Arrays ◽

Rigorous Coupled Wave ◽

Soi Substrates ◽

Coupled Wave

AbstractIn this paper, we present a rigorous coupled-wave analysis (RCWA) of absorption enhancement in all-silicon (Si) photodiodes with integrated hole arrays of different shapes and dimensions. The RCWA method is used to analyze the light propagation and trapping in the photodiodes on both Si-on-insulator (SOI) and bulk Si substrates for the datacom wavelength at about 850 nm. Our calculation and measurement results show that funnel-shaped holes with tapered sidewalls lead to low back-reflection. A beam of light undergoes a deflection subsequent to the diffraction in the hole array and generates laterally propagating waves. SOI substrates with oxide layers play an important role in reducing the transmission loss, especially for deflected light with higher-order diffraction from the hole array. Owing to laterally propagating modes and back-reflection on the SiO2 film, light is more confined in the thin Si layer on the SOI substrates compared to that on the bulk Si substrates. Experimental results based on fabricated devices support the predictions of the RCWA. Devices are designed with a 2-μm-thick intrinsic layer, which ensures ultrafast impulse response (full-width at half-maximum) of 30 ps. Measurements for integrated photodiodes with funnel-shaped holes indicate an enhanced external quantum efficiency of more than 55% on the SOI substrates. This represents more than 500% improvement compared to photodiodes without integrated phototrapping nanoholes.

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Broadband solar absorption enhancement via periodic nanostructuring of electrodes

Scientific Reports ◽

10.1038/srep02928 ◽

2013 ◽

Vol 3 (1) ◽

Cited By ~ 57

Author(s):

Michael M. Adachi ◽

André J. Labelle ◽

Susanna M. Thon ◽

Xinzheng Lan ◽

Sjoerd Hoogland ◽

...

Keyword(s):

Absorption Enhancement ◽

Solar Absorption

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Material and Device Issues of AlGaN/GaN HEMTs on Silicon Substrates

MRS Proceedings ◽

10.1557/proc-743-l9.1 ◽

2002 ◽

Vol 743 ◽

Author(s):

P. Javorka ◽

A. Alam ◽

M. Marso ◽

M. Wolter ◽

A. Fox ◽

...

Keyword(s):

Heat Dissipation ◽

Current Gain ◽

Commercial Application ◽

Material Structure ◽

Silicon Substrates ◽

Trap Level ◽

Si Substrates ◽

Channel Temperature ◽

Rf Devices ◽

Gan Hemts

ABSTRACTResults on the preparation and properties of AlGaN/GaN HEMTs on silicon substrates are presented and selected issues related to the material structure and device performance devices are discussed. Virtually crack-free AlGaN/GaN heterostructures (xAlN ≅ 0.25), with low surface roughness (rms of 0.64 nm), ns ≅ 1×1013 cm−2 and μ ≅ 1100 cm2/V s at 300 K, were grown by LP-MOVPE on 2-inch (111)Si substrates. HEMT devices with Lg = 0.3–0.7 μm were prepared by conventional device processing steps. Photoionization spectroscopy measurements have shown that a trap level of 1.85 eV, additional to two levels of 2.9 and 3.2 eV found before on GaN-based HEMTs on sapphire, is present in the structures investigated. Self-heating effects were studied by means of temperature dependent dc measurements. The channel temperature of a HEMT on Si increases with dissipated power much slower than for similar devices on sapphire substrate (e.g. reaches 95 and 320 °C on Si and sapphire, respectively, for 6 W/mm power). Prepared AlGaN/GaN/Si HEMTs exhibit saturation currents up to 0.91 A/mm, a good pinch-off, peak extrinsic transconductances up to 150 mS/mm and static heat dissipation capability up to ∼16 W/mm. Unity current gain frequencies fT up to 21 and 32 GHz were obtained on devices with gate length of 0.7 and 0.5 μm, respectively. The saturation current and fT values are comparable to those known for similar devices using sapphire and SiC substrates. Properties of AlGaN/GaN/Si HEMTs investigated show that this technology brings a prospect for commercial application of high power rf devices.

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Heat transfer and structure stress analysis of micro packaging component of high power light emitting diode

Thermal Science ◽

10.2298/tsci1305277h ◽

2013 ◽

Vol 17 (5) ◽

pp. 1277-1283 ◽

Cited By ~ 3

Author(s):

Chih-Neng Hsu ◽

Yu-Hao Chang ◽

Chang-Yuan Liu ◽

Shih-Hao Fang ◽

Chun-Chieh Huang

Keyword(s):

Heat Transfer ◽

Stress Analysis ◽

High Power ◽

Silicon Substrate ◽

Heat Dissipation ◽

Light Emitting Diode ◽

Material Structure ◽

Light Emitting ◽

Micro Scale ◽

Chip Temperature

This paper focuses on the heat transfer and structural stress analysis of the micro- scale packaging structure of a high-power light emitting diode. The thermal-effect and thermal-stress of light emitting diode are determined numerically. Light emitting diode is attached to the silicon substrate through the wire bonding process by using epoxy as die bond material. The silicon substrate is etched with holes at the bottom and filled with high conductivity copper material. The chip temperature and structure stress increase with input power consumption. The micro light emitting diode is mounted on the heat sink to increase the heat dissipation performance, to decrease chip temperature, to enhance the material structure reliability and safety, and to avoid structure failure as well. This paper has successfully used the finite element method to the micro-scale light emitting diode heat transfer and stress concentration at the edges through etched holes.

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Surface wetting of the C/SiC brake lining with micro-scale heat dissipation fins to cool off the brake system: Influence of the fibre ending orientation and fin interval

Ceramics International ◽

10.1016/j.ceramint.2017.05.101 ◽

2017 ◽

Vol 43 (14) ◽

pp. 10805-10816 ◽

Cited By ~ 3

Author(s):

M.L. Wu ◽

C.Z. Ren ◽

H.Z. Xu ◽

C.L. Zhou

Keyword(s):

Heat Dissipation ◽

Brake System ◽

Surface Wetting ◽

Micro Scale ◽

Fibre Ending ◽

Brake Lining

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Wavelet Based Nano-Texture Structures for Thin Film PV Cells

Volume 9: Micro- and Nano-Systems Engineering and Packaging, Parts A and B ◽

10.1115/imece2012-87045 ◽

2012 ◽

Author(s):

Shima Hajimirza ◽

John R. Howell

Keyword(s):

Thin Film ◽

Light Trapping ◽

Front Surface ◽

Numerical Approach ◽

Inverse Optimization ◽

Absorption Enhancement ◽

Metallic Surface ◽

Periodic Patterns ◽

Orthonormal Bases ◽

Finite Set

Light trapping is an important technique in increasing the efficiency of solar cells. Inverse optimization is a systematic numerical approach that allows us to find the limits of light trapping more efficiently. It is an alternative to exhaustive search simulations or experimental measurements. In this work, we use inverse optimization to study light trapping in thin film amorphous silicon cells textured by periodic patterns of metallic surface grating. We use a finite set of Haar wavelets to describe a general form of grating structure composed of multiple rectangular nano-strips. We use global simulated annealing optimization to find the coefficients of the wavelets basis for optimal absorption enhancement in thin film silicon. The motivation for choosing wavelet basis (vis-a-vis other orthonormal bases such as Fourier) is the feasibility of fabricating the resulting nano-structures. The resulting improvement in the number of absorbed photons is around 130% for wavelength range of 300–700nm, which is significantly better than the previous results using simple front surface nano-strips. In addition, we use statistical analysis to evaluate the sensitivity of the characteristics of the resulting structure to numerical uncertainties.

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