Investigation of semiconductor photoconverters, transparent in the infrared region of the solar spectrum

Passive radiative cooling, which cools an item without any electrical input, has drawn much attention in recent years. In many radiative coolers, silica is widely used due to its high emissivity in the mid-infrared region. However, the performance of a bare silica film is poor due to the occurrence of an emitting dip (about 30% emissivity) in the atmospheric transparent window (8–13 μm). In this work, we demonstrate that the emissivity of silica film can be improved by sculpturing structures on its surface. According to our simulation, over 90% emissivity can be achieved at 8–13 μm when periodical silica deep grating is applied on a plane silica film. With the high emissivity at the atmospheric transparent window and the extremely low absorption in the solar spectrum, the structure has excellent cooling performance (about 100 W/m2). The enhancement is because of the coupling between the incident light with the surface modes. Compared with most present radiative coolers, the proposed cooler is much easier to be fabricated. However, 1-D gratings are sensitive to incident polarization, which leads to a degradation in cooling performance. To solve this problem, we further propose another radiative cooler based on a silica cylinder array. The new cooler’s insensitivity to polarization angle and its average emissivity in the atmospheric transparent window is about 98%. Near-unit emissivity and their simple structures enable the two coolers to be applied in real cooling systems.

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Symmetric Compound Parabolic Concentrator with Indium Tin Oxide Coated Glass as Passive Cooling System for Photovoltaic Application

Journal of Solar Energy ◽

10.1155/2016/8264247 ◽

2016 ◽

Vol 2016 ◽

pp. 1-12

Author(s):

Damasen Ikwaba Paul

Keyword(s):

Tin Oxide ◽

Indium Tin Oxide ◽

Visible Region ◽

Solar Spectrum ◽

Infrared Region ◽

Passive Cooling ◽

Photovoltaic Module ◽

Coated Glass ◽

Compound Parabolic Concentrator ◽

Exit Aperture

One problem with concentrating photovoltaic systems is the increase in operating photovoltaic module temperature which results in power output reduction. Indium Tin Oxide (ITO) coated glasses exhibit both high transmittance in the visible region and high reflectance in the infrared region of the solar spectrum. Such materials can be used as selective windows in photovoltaic modules operating under concentrating system enabling passive cooling. In this paper, a Heat Reflector Window (HRW) consisting of a glass coated with 180 nm layer of ITO was experimentally tested. The ITO coated glass had a transmittance of about 85% in the visible region and over 80% reflectance in the infrared region of the solar spectrum and was placed at the exit aperture of a Compound Parabolic Concentrator (CPC). Results indicate that the temperature of a photovoltaic module under CPC with the HRW was reduced by about 50% as compared to a similar photovoltaic module with CPC but without the HRW. However, due to presence of the HRW at the exit aperture of the CPC, the photovoltaic module with the CPC and HRW received less solar irradiance compared to a similar photovoltaic module with the CPC but without HRW.

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Convective Lineshifts in the Infrared Region of the Solar Spectrum

International Astronomical Union Colloquium ◽

10.1017/s0252921100048697 ◽

1999 ◽

Vol 170 ◽

pp. 291-296

Author(s):

Devon Hamilton ◽

J. B. Lester

Keyword(s):

Visible Region ◽

Solar Spectrum ◽

Infrared Region ◽

The Sun ◽

The Past ◽

Large Size ◽

Convective Motions ◽

Solar Type ◽

Line Positions ◽

Different Levels

AbstractConvective motions in the photospheres of the Sun and solar-type stars can be studied using spectral line asymmetries via line bisectors and line shifts. Over the past few years there has been an improvement in the precision of the line positions for Fe I, CO and OH. These improved positions can be combined with recent high resolution infrared spectra of the Sun to examine how their convective line asymmetries behave with respect to observable line parameters, such as wavenumber and depth. We have completed a survey of convective line shifts for over 650 Fe I lines, 1320 CO lines and 80 OH lines, between 0.9 and 11 μm. The behavior of the distributions of these features, with respect to observed characteristics, is examined. The use of different species allows for an exploration of convective motions at different levels in the solar atmosphere. The large size of the sample allows for a more complete statistical understanding of the distributions. This work complements surveys of line asymmetries in the visible region of the Solar spectrum, and provides a foundation for further studies of convective motions in the spectra of other stars.

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Broadband photon absorption in self-assembled networks of multiphase oxides of titanium

10.32920/ryerson.14653674.v1 ◽

2021 ◽

Author(s):

Pooja Thakur

Keyword(s):

Near Infrared ◽

Experimental Studies ◽

Three Dimensional ◽

Solar Spectrum ◽

Infrared Region ◽

Single Step ◽

Photon Absorption ◽

Visible Range ◽

Ultraviolet Region ◽

Self Assembled

Titanium -dioxide (TiO2) has garnered immense interest as a potential photon absorber after the discovery of its photocatalytic properties. However, its absorption is limited to the ultraviolet region of the solar spectrum. Despite numerous efforts being made, the challenge to extend its absorption capability to the entire visible and near infrared region (vis-NIR) still exists, which together constitute about 90 % of the solar spectrum. In this dissertation, a multiphase nano TiOx network, rich in defects and oxygen vacancies, has been presented which can absorb photons over a broader range of the solar spectrum. Experimental studies were initially conducted to phase functionalise titanium towards enhanced photon absorption via a single step, ultrashort laser pulse material interaction process. This phase functionalised titanium, characterised to be uniquely composed of multiple oxide phases of titanium, can effectively absorb photons in the vis-NIR region. Using the above study as a template, a complex three-dimensional self-assembled nano network composed of similar multiphase titanium oxides, was then synthesised. Free of any external dopants, it exhibits a remarkable absorption of photons ranging from 300-1000 nm. To further improve the absorptive properties of this ‘multiphase nano TiOx network’, particularly in the lower visible range, the phenomenon of Surface Plasmon Resonance was utilised via its hybridisation with gold and gold/palladium alloy. This successfully resulted in further optimisation of its absorption. The final study of the multiphase nano TiOx was done to understand the fundamental physics behind its broadened photon absorptive behaviour. The condition of synthesis was varied by introducing various contrasting plasma environments. Pronounced disorders and oxygen defects of varying degrees within the crystalline structure were observed. The enhanced and broadened absorption spectrum achieved was attributed to such defects and disorders. The research done in this thesis demonstrates a unique nanomaterial based on multiple oxides phases of titanium that is capable of absorbing photons both in the visible and NIR regions. The contribution made towards the synthesis, investigation and subsequent manipulation of the self-assembled multiphase nano TiOx network can thus be exploited in various photon harvesting applications like photovoltaics and photo catalysis, where such a broadband photon absorption is desirable.

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On the phosphorograph of a solar spectrum, and the lines of its infrared region

American Journal of Science ◽

10.2475/ajs.s3-21.123.171 ◽

1881 ◽

Vol s3-21 (123) ◽

pp. 171-182

Author(s):

J. W. Draper

Keyword(s):

Solar Spectrum ◽

Infrared Region

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Evaluation of a PV-TEG Hybrid System Configuration for an Improved Energy Output: A Review

International Journal of Renewable Energy Development ◽

10.14710/ijred.0.33917 ◽

2020 ◽

Author(s):

Umar Abubakar Saleh ◽

Muhammad Akmal Johar ◽

Siti Amely Binti Jumaat ◽

Muhammad Nazri Rejab ◽

Wan Akashah Wan Jamaludin

Keyword(s):

Hybrid System ◽

Solar Spectrum ◽

Infrared Region ◽

Energy Output ◽

System Configuration ◽

Thermoelectric Effects ◽

Energy Demands ◽

Thermoelectric Energy ◽

Thermoelectric Systems ◽

Hybrid Photovoltaics

The development of sustainable energy, in particular solar energy, is essential to achieving future energy demands. Solar radiation and heat energy will provide the required electricity needed in daily life. Photovoltaics and thermoelectric energy conversion have been developed over the years. Photovoltaics also converts the ultraviolet-visible areas of the solar spectrum, while thermoelectric uses the Infrared region. Combination of photovoltaic and thermoelectric effects will expand the efficient spectrum range. Research has recently been conducted on hybrid photovoltaic-thermoelectric systems to increase conversion efficiency. The purpose of this work is to review the primary concepts of the hybrid photovoltaics-thermoelectric generator. The work summarises the different methods used to combine hybrid photovoltaic-thermoelectric systems. A proposed PV-TEG Hybrid system using shingle in between the PV and the TEG is presented. Further research on the hybrid system is also encouraged due to encouraging performance

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Photochemical α-Aminonitrile Synthesis using Zn Phthalocyanines as Near Infrared Photocatalysts

10.26434/chemrxiv-2021-cvcgw ◽

2021 ◽

Author(s):

Caroline Grundke ◽

Rodrigo Silva ◽

Winald Kitzmann ◽

Katja Heinze ◽

Kleber de Oliveira ◽

...

Keyword(s):

Near Infrared ◽

Photophysical Properties ◽

Solar Spectrum ◽

Structural Similarity ◽

Infrared Region ◽

Infrared Light ◽

Near Infrared Light ◽

High Tendency ◽

Long Time ◽

Light Absorbers

While photochemical transformations with sunlight almost exclusively utilize the UV-Vis part of the solar spectrum, the majority of the photons emitted by the sun have frequencies in the near-infrared region. Phthalocyanines show high structural similarity to the naturally occurring light harvesting porphyrins, chlorins and mainly bacteriochlorins, and are also known for being efficient and affordable near-infrared light absorbers as well as triplet sensitizers for the production of singlet oxygen. Although having been neglected for a long time in synthetic organic chemistry due to their low solubility and high tendency towards aggregation, their unique photophysical properties and chemical robustness make phthalocyanines attractive photocatalysts for the application in near-infrared light-driven synthesis strategies. Herein, we report a cheap, simple and efficient photocatalytic protocol, which is easily scalable under continuous flow conditions. Various phthalocyanines were studied as near-infrared photosensitizers in oxidative cyanations of tertiary amines to generate α-aminonitriles, a synthetically versatile compound class.

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Broadband photon absorption in self-assembled networks of multiphase oxides of titanium

10.32920/ryerson.14653674 ◽

2021 ◽

Author(s):

Pooja Thakur

Keyword(s):

Near Infrared ◽

Experimental Studies ◽

Three Dimensional ◽

Solar Spectrum ◽

Infrared Region ◽

Single Step ◽

Photon Absorption ◽

Visible Range ◽

Ultraviolet Region ◽

Self Assembled

Titanium -dioxide (TiO2) has garnered immense interest as a potential photon absorber after the discovery of its photocatalytic properties. However, its absorption is limited to the ultraviolet region of the solar spectrum. Despite numerous efforts being made, the challenge to extend its absorption capability to the entire visible and near infrared region (vis-NIR) still exists, which together constitute about 90 % of the solar spectrum. In this dissertation, a multiphase nano TiOx network, rich in defects and oxygen vacancies, has been presented which can absorb photons over a broader range of the solar spectrum. Experimental studies were initially conducted to phase functionalise titanium towards enhanced photon absorption via a single step, ultrashort laser pulse material interaction process. This phase functionalised titanium, characterised to be uniquely composed of multiple oxide phases of titanium, can effectively absorb photons in the vis-NIR region. Using the above study as a template, a complex three-dimensional self-assembled nano network composed of similar multiphase titanium oxides, was then synthesised. Free of any external dopants, it exhibits a remarkable absorption of photons ranging from 300-1000 nm. To further improve the absorptive properties of this ‘multiphase nano TiOx network’, particularly in the lower visible range, the phenomenon of Surface Plasmon Resonance was utilised via its hybridisation with gold and gold/palladium alloy. This successfully resulted in further optimisation of its absorption. The final study of the multiphase nano TiOx was done to understand the fundamental physics behind its broadened photon absorptive behaviour. The condition of synthesis was varied by introducing various contrasting plasma environments. Pronounced disorders and oxygen defects of varying degrees within the crystalline structure were observed. The enhanced and broadened absorption spectrum achieved was attributed to such defects and disorders. The research done in this thesis demonstrates a unique nanomaterial based on multiple oxides phases of titanium that is capable of absorbing photons both in the visible and NIR regions. The contribution made towards the synthesis, investigation and subsequent manipulation of the self-assembled multiphase nano TiOx network can thus be exploited in various photon harvesting applications like photovoltaics and photo catalysis, where such a broadband photon absorption is desirable.

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Note on the spectral classification of carbon stars in the photographic infrared region

Symposium - International Astronomical Union ◽

10.1017/s0074180900053080 ◽

1966 ◽

Vol 24 ◽

pp. 21-23

Author(s):

Y. Fujita

Keyword(s):

Infrared Region ◽

Spectral Classification ◽

Carbon Stars

We have investigated the spectrograms (dispersion: 8Å/mm) in the photographic infrared region fromλ7500 toλ9000 of some carbon stars obtained by the coudé spectrograph of the 74-inch reflector attached to the Okayama Astrophysical Observatory. The names of the stars investigated are listed in Table 1.

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