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9 pages, 3052 KiB

Open AccessArticle

A Method of Improving the Structural Color Quality of HfO₂ Grating Based on Thin Film Filter

by Chi Song, Xin Zhang, Mingyang Li, Zhenhao Liu, Henan Hu and Zizheng Li

Coatings 2022, 12(11), 1657; https://doi.org/10.3390/coatings12111657 - 31 Oct 2022

Cited by 1 | Viewed by 1328

In order to eliminate the influence of the high-order magnetic dipole modes in the short-wave range of the high-refractive-index dielectric grating, we propose a thin film filter to cut off the “useless” short-wave. In this way, the high-order magnetic dipole can be suppressed, [...] Read more.

In order to eliminate the influence of the high-order magnetic dipole modes in the short-wave range of the high-refractive-index dielectric grating, we propose a thin film filter to cut off the “useless” short-wave. In this way, the high-order magnetic dipole can be suppressed, and the quality of the structure color is highly improved after the thin film filter cut off the incident light in the non-resonant band. The combined application of the thin film filter and the grating filter not only avoids the problem of too big film layer thickness, but also reduces the manufacturing process cost. For example, the film system (basic film system 0.5 L H 0.5 L) and thickness of green, 15° and 45° incident film filters are 21 layers, 1.76 μm and 41 layers, 4.02 μm. The color coordinates corresponding to the calculation results occupy a large area on the Commission Internationale de l’Eclairage 1931 (CIE 1931) chromaticity diagram, which proves that this design scheme can effectively improve the structural color quality. This method obtains excellent theoretical simulation results. This has important implications for high-end imaging equipment and sensors. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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12 pages, 1177 KiB

Open AccessArticle

Design of 1D Photonic Crystals Sustaining Optical Surface Modes

by Valery Konopsky

Coatings 2022, 12(10), 1489; https://doi.org/10.3390/coatings12101489 - 6 Oct 2022

Cited by 4 | Viewed by 1800

Abstract

An impedance approach has been implemented to design truncated 1D photonic crystals, sustaining optical surface modes, with any predetermined wavelength and wavevector. The implementation is realized as a free Windows program that calculates both the thicknesses of the double layers and the thickness [...] Read more.

An impedance approach has been implemented to design truncated 1D photonic crystals, sustaining optical surface modes, with any predetermined wavelength and wavevector. The implementation is realized as a free Windows program that calculates both the thicknesses of the double layers and the thickness of the final truncated layer at given refractive indices of the layers. The dispersion of the refractive indices can be given in the form of the Sellmeier/Drude formulas or in the form of a wavelength-n-k table. For mixed layers, the Maxwell Garnett theory can be used. This approach is suitable for studying and visualizing the field distribution inside photonic crystals, dispersion, and other aspects of the designed structures that sustain optical surface modes. Therefore, this program should promote scientific development and implementation of practical applications in this area. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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10 pages, 3518 KiB

Open AccessArticle

Structural and Optical Properties of CuO Thin Films Synthesized Using Spray Pyrolysis Method

by Oleksii Diachenko, Jaroslav Kováč, Jr., Oleksandr Dobrozhan, Patrik Novák, Jaroslav Kováč, Jaroslava Skriniarova and Anatoliy Opanasyuk

Coatings 2021, 11(11), 1392; https://doi.org/10.3390/coatings11111392 - 15 Nov 2021

Cited by 29 | Viewed by 3075

Abstract

Copper oxide thin films were obtained using pulsating spray pyrolysis method. The morphological, structural, and optical properties of fabricated films were studied. X-ray analysis revealed that the CuO thin films are single-phase. The study of films morphology by SEM and AFM methods showed [...] Read more.

Copper oxide thin films were obtained using pulsating spray pyrolysis method. The morphological, structural, and optical properties of fabricated films were studied. X-ray analysis revealed that the CuO thin films are single-phase. The study of films morphology by SEM and AFM methods showed that the obtained films have a fairly high surface roughness and contain grains of different shapes and sizes. It was found that the obtained films of copper oxide have high values of the absorption coefficient, which confirms the possibility of their use as absorbing layers for solar cells. The obtained values of the optical band gap of the material are in the range from 1.45 eV to 1.60 eV. Raman spectroscopy revealed three modes A_1g, B_1g, and B_2g, of the crystal structure of monoclinic CuO. The devices based on p-type copper oxide are promising for solar cells fabrication because they can reduce production costs, due to their low cost and inexpensive production methods compared to silicon solar cells fabrication. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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11 pages, 2360 KiB

Open AccessArticle

Optical Absorption in Si:H Thin Films: Revisiting the Role of the Refractive Index and the Absorption Coefficient

by Jarmila Müllerová, Pavol Šutta and Michaela Holá

Coatings 2021, 11(9), 1081; https://doi.org/10.3390/coatings11091081 - 7 Sep 2021

Cited by 3 | Viewed by 3199

Abstract

This paper reports on absorption properties of thin films of hydrogenated amorphous and microcrystalline silicon considered for absorption-based applications, such as solar cell, photodetectors, filters, sensors, etc. A series of four amorphous and four microcrystalline samples PECVD deposited under varied hydrogen dilution was [...] Read more.

This paper reports on absorption properties of thin films of hydrogenated amorphous and microcrystalline silicon considered for absorption-based applications, such as solar cell, photodetectors, filters, sensors, etc. A series of four amorphous and four microcrystalline samples PECVD deposited under varied hydrogen dilution was under consideration. Various absorption metrics, based separately on the absorption coefficient and the refractive index (single pass absorption, optical path length, classical light trapping limit) or direct absorptance calculated by the Yablonovitch concept based on a mutual role of them were examined and compared. Differences in absorption abilities are related to the evolving thin film microstructure. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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17 pages, 6412 KiB

Open AccessArticle

Optical Losses of Frontal Layers in Superstrate CdS/CdTe Solar Cells Using OPAL2

by Nowshad Amin, Mohammad Rezaul Karim and Zeid Abdullah ALOthman

Coatings 2021, 11(8), 943; https://doi.org/10.3390/coatings11080943 - 6 Aug 2021

Cited by 2 | Viewed by 2487

Abstract

In this paper, optical losses in CdS/CdTe solar cells are calculated on the basis of the designated reflective index of various frontal layers using an OPAL2 calculator for the first time. Two types of glass (0.1 mm ultra-thin Schott and 1.1 mm standard [...] Read more.

In this paper, optical losses in CdS/CdTe solar cells are calculated on the basis of the designated reflective index of various frontal layers using an OPAL2 calculator for the first time. Two types of glass (0.1 mm ultra-thin Schott and 1.1 mm standard borosilicate glass) were assumed to be coated by different Transparent-Conducting-Oxides (TCOs) such as SnO₂:F, ZnO:Al, and ITO forming frontal layers for CdS/CdTe solar cells in superstrate configuration. Absorption, reflectance, transmittance, and consequently optical bandgap energies are calculated as a function of common thicknesses, used in the literature. The results show that an increase in TCO thickness led to a decrease in optical band gap as well as an enhancement in contact potential difference, which can deteriorate device performance. The optimum thickness of 100 nm for SnO₂:F was calculated, while 200 nm for ZnO:Al and ITO show reasonable optical losses caused by reflections at the interfaces’ and the layer’s absorption. It is seen that 80 to 150 nm CdS on ITO might be an effective range to satisfy a high short circuit current and low defect densities at the CdS/CdTe interface. Finally, a minimum 2 μm thickness for the CdTe on the ultra-thin Schott glass coated by optimum layers can result in the highest short circuit current of 28.69 mA/cm². This work offers a practical equivalent strategy to be applied for any superstrate solar cells containing TCO and CdS frontal layers. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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14 pages, 14010 KiB

Open AccessArticle

Effect of Slit Channel Width of a Shim Embedded in Slot-Die Head on High-Density Stripe Coating for OLEDs

by Dongkyun Shin, Jinyoung Lee and Jongwoon Park

Coatings 2020, 10(8), 772; https://doi.org/10.3390/coatings10080772 - 8 Aug 2020

Cited by 7 | Viewed by 4418

Abstract

With an attempt to achieve high-density fine organic stripes for potential applications in solution-processable organic light-emitting diodes (OLEDs), we have performed slot-die coatings using a shim with slit channels in various shapes (rectangular-shaped narrow, rectangular-shaped wide, and reversely tapered channels) in the presence [...] Read more.

With an attempt to achieve high-density fine organic stripes for potential applications in solution-processable organic light-emitting diodes (OLEDs), we have performed slot-die coatings using a shim with slit channels in various shapes (rectangular-shaped narrow, rectangular-shaped wide, and reversely tapered channels) in the presence of narrow µ-tips. Based on hydraulic-electric circuit analogy, we have analyzed the fluid dynamics of an aqueous poly (3,4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT:PSS). It is observed that the coating speed can be increased and the stripe width can be reduced using a shim with rectangular-shaped wide slit channels. It is attributed that the hydraulic resistance is decreased and thus more fluid can reach a substrate through µ-tips. This behavior is consistent with the simulation result of the equivalent electrical circuit with a DC voltage source representing a pressure source. Using the shim with 150-µm-wide slit channels, we have successfully fabricated 200 PEDOT:PSS stripes within the effective coating width (150 mm) and 160 OLED stripes (34 stripes per inch) with the luminance of 325 cd/m² at 5 V. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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14 pages, 4350 KiB

Open AccessArticle

An Investigation on Structural and Optical Properties of Zn_1−xMg_xS Thin Films Deposited by RF Magnetron Co-Sputtering Technique

by Muhammad Shahriar Bashar, Yulisa Yusoff, Siti Fazlili Abdullah, Mashudur Rahaman, Puvaneswaran Chelvanathan, Abdul Gafur, Farid Ahmed, Md Akhtaruzzaman and Nowshad Amin

Coatings 2020, 10(8), 766; https://doi.org/10.3390/coatings10080766 - 6 Aug 2020

Cited by 5 | Viewed by 2924

Abstract

In this paper, Zn_1−xMg_xS thin films were co-sputtered on glass substrates using ZnS and MgS binary target materials under various applied RF power. The compositional ratio of Zn_1−xMg_xS films was varied by changing [...] Read more.

In this paper, Zn_1−xMg_xS thin films were co-sputtered on glass substrates using ZnS and MgS binary target materials under various applied RF power. The compositional ratio of Zn_1−xMg_xS films was varied by changing the RF power at an elevated temperature of 200 °C. The structural and optical properties were studied in detail. The structural analysis shows that the co-sputtered Zn_1−xMg_xS thin films have a cubic phase with preferred orientation along the (111) plane. The lattice constant and ionicity suggest the presence of a zincblende structure in Zn_1−xMg_xS thin films. Zn_1−xMg_xS thin films have transmittance over 76%. The extrapolation of optical characteristics indicates that direct bandgaps, ranging from 4.39 to 3.25 eV, have been achieved for the grown Zn_1−xMg_xS films, which are desirable for buffer or window layers of thin film photovoltaics. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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6 pages, 1340 KiB

Open AccessCommunication

Pulsed Laser Deposition of In_0.1Ga_0.9N Nanoshapes by Nd:YAG Technique

by Sara Gad, Marwa Fathy, Yehia Badr and Abd El-Hady B. Kashyout

Coatings 2020, 10(5), 465; https://doi.org/10.3390/coatings10050465 - 10 May 2020

Cited by 3 | Viewed by 1975

Abstract

In_0.1Ga_0.9N thin film was grown on a cheap glass substrate by the Nd:YAG pulsed laser deposition technique. The In_0.1Ga_0.9N thin films show the semi-crystalline structure as observed with X-ray diffraction (XRD). The surface morphology has [...] Read more.

In_0.1Ga_0.9N thin film was grown on a cheap glass substrate by the Nd:YAG pulsed laser deposition technique. The In_0.1Ga_0.9N thin films show the semi-crystalline structure as observed with X-ray diffraction (XRD). The surface morphology has a non-dense layer with both scattered nanospheres and agglomerated particles. These nanospheres tended to grow randomly on the glass substrate, as observed with field emission scanning electron microscopy (FESEM). The direct bandgap energy for In_0.1Ga_0.9N thin film was 2.08 eV, which is calculated using photoluminescence (PL) measurements. The Raman measurements illustrated two sets of phonon modes as A1(LO) and E2 high vibrational modes that are observed. The resonance behavior of the A1(LO) mode is experimentally verified and studied under laser light energy of 532 nm. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Thin Films for Photonic Applications)

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