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1

Quantum dots for temperature sensing

Doskaliuk Natalia, Lukan Yuliana, Khalavka Yuriy

Scientiae Radices

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2023

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Vol. 2, Iss. 2

93--111

EN

Quantum dots are three-dimensional nanoparticles of semiconductors with typical sizes ranging from 2 to 10 nm. Due to the quantum confinement effect the energy gap increase with the size decreasing resulting in size-depended and fine-tunable optical characteristics. Besides this, the energy structure of a quantum dot with a certain size is highly sensitive to environmental conditions. These specific properties open a wide range of applications starting from optical and optoelectronic devices and ending with biosensing and life science. Temperature is one of those parameters influencing strongly on the optical properties of semiconductor nanocrystals, which make them promising materials for temperature sensing, more often using a fluorescent response. Compared to the conventional organic dyes already applied in this field, quantum dots exhibit a set of advantages, such as high quantum yield and photostability, long fluorescence lifetime, higher Stokes shift, and ability to surface functionalization with targeted organic molecules aimed to provide them biocompatibility. In this review, we briefly discuss the properties of II-VI and assumingly less toxic I-III-VI quantum dots, mechanisms of temperature-induced fluorescence response, and the feasibility of their practical application in the field of thermal sensing.

2

A detailed review on Si, GaAs, and CIGS/CdTe based solar cells and efficiency comparison

Du John H. Victor, Moni D. Jacquline, Gracia D.

Przegląd Elektrotechniczny

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2020

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R. 96, nr 12

9--18

EN

A solar cell is technically known as a photovoltaic device which converts light energy into an electric energy by the phenomenon called photovoltaic effect. Solar cells produce renewable energy and serve as a great substitute for conventional sources of energy such as petroleum, coal and natural gas. Solar cell is suitable for powering satellites due to its light weight and durability for several years, having ability to operate even in the vacuum space. It is also used in solar warm air electric power plants and every other PV powered devices ranging from heating systems, lighting, automobile to solar updraft towers and etc. It is of utmost demand to support research and development of renewable energy resources that would successfully power the world in the future without destroying the environment as the planet earth needs reduction in greenhouse gas emission. Immense progress has been observed over the years on several photovoltaic materials and devices based on conversion efficiencies.. This survey primarily focusses on different techniques and technologies analysed from the other cited references to enhance the working of a solar cell like selection of the most suitable material for each layer, various processing techniques and modifying the layer thickness of buffer. This review paper summarizes solar cell materials like Gallium Arsenide (GaAs), Silicon (Si), Cu(In,Ga)(S,Se2) (CIGS) and Cadmium Telluride (CdTe) that provide higher efficiencies when compared to other materials. In summation, it is understood that Gallium Arsenide solar cell provides highest efficiency when compared to Si, CIGS and CdTe based one junction solar cell. Factors such as, efficiency (ƞ), open circuit voltage (Voc), short circuit current density (Jsc) & fill factor (FF) have been analysed for the study of modeling, simulation and fabrication of solar cell. Detailed survey has been presented in this paper on different types of solar cells that would help the researchers to do more research on these solar cells.

PL

W artykule dokonao przeglądu i porównania różnych technologgi ogniw fotowoltaicznych. Przedstawiono ogniwa krzemowe, ogniwa bazujące na CdTe i CIGS oraz ogniwa bazujące na Gallium Arsenide (GaAs). W każdej grupie przedstawiono i porównano osiągane obecnie parametry I właściwości.

3

Development of chalcogenide solar cells : importance of CdS window layer

Lilhare D., Khare A.

Opto-Electronics Review

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2020

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Vol. 28, No. 1

43--63

EN

The solar photovoltaic technology is one of the renewable technologies with the potential to shape a future-proof, reliable, scalable and affordable electricity system. It is important to provide better resources for any upcoming technology. CdS/CdTe thin films have long been considered as one enticing option for reliable and cost-effective solar cells to be developed. N-type CdS as a transparent window layer in heterojunction structures is one of the best choices for CdTe cells. In a solar cell structure, window layer material plays a very crucial role to improve its performance. For this reason, this review focuses on the basic and significant aspects such as importance of the window layer thickness, degradation effect, use of nano-wire arrays, and an ammonia-free process to deposit the window layer. Also, an attempt has been made to analyze various processes improving window layer properties. Necessary discussions have been included to review the impact of solar cell parameters on the above aspects. It is anticipated that this review article will fulfill the requirement of knowledge to be used in the fabrication of CdS/CdTe solar cells.

4

Structural and luminescent properties of Fe3+ doped PVA capped CdTe nanoparticles

Ravindranadh K., Rao M. C.

Materials Science Poland

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2017

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Vol. 35, No. 2

390--397

EN

During recent decades, magnetic and semiconductor nanoparticles have attracted significant attention of scientists in various fields of engineering, physics, chemistry, biology and medicine. Fe3+ doped PVA capped CdTe nanoparticles were prepared by co-precipitation method and characterized by powder X-ray diffraction, SEM, TEM, FT-IR, optical, EPR and PL techniques to collect the information about the crystal structure, coordination/local site symmetry of doped Fe3+ ions in the host lattice and the luminescent properties of prepared sample. Powder XRD data revealed that the crystal structure belongs to a cubic system and its lattice cell parameters were evaluated. The average crystallite size was estimated to be 8 nm. The morphology of prepared samples was analyzed by using SEM and TEM investigations. Functional groups of the prepared sample were observed in FT-IR spectra. Optical absorption and EPR studies have shown that on doping, Fe3+ ions enter the host lattice in octahedral site symmetry. PL studies of Fe3+ doped PVA capped CdTe nanoparticles revealed UV and blue emission bands. CIE chromaticity coordinates were also calculated from the emission spectrum of Fe3+ doped PVA capped CdTe nanoparticles.

5

Aktywność defektów w pomiarach elektrycznych i optycznych złączy fotowoltaicznych na bazie CdTe

Zielony E., Morawski M., Racino A., Płaczek-Popko E., Gumienny Z., Chusnutdinow S., Karczewski G.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 9

43--46

PL

W niniejszym artykule przedstawione zostały wyniki badań defektów w strukturach fotowoltaicznych na bazie CdTe, otrzymanych techniką epitaksji z wiązek molekularnych (MBE). Do charakteryzacji defektów w badanych złączach wykorzystano różne metody pomiarowe, takie jak: charakterystyki prądowo-napięciowe, niestecjonarna spektroskopia głębokich poziomów (DLTS) i fotoluminescencja (PL), mierzone w szerokim zakresie temperatur. Pokazano, że sprawności badanych diod są stosunkowo niskie, na co mają wpływ defekty występujące w ich strukturze. W oparciu o wyniki pomiarów widm DLTS i PL wyznaczono parametry defektów oraz określono źródło ich pochodzenia.

EN

In this article the results of investigations of defects in photovoltaic structures based on CdTe grown by the molecular beam epitaxy (MBE) technique have been presented. For the characterization of defects in the studied junctions various measurement methods have been used, such as: current-voltage characteristics, deep level transient spectroscopy (DLTS) and photoluminescence (PL), measured in a broad temperature range. It has been shown that the efficiency of the investigated diodes are relatively low, what is caused by the defects present in their structure. Based on the results of the DLTS- and PL spectra the parameters of defects have been determined and their possible origin has been discussed.

6

Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

Choi H., Kim H. S., Oh J.-H., Kim D. J., Kim Y. S., Chai J.-S., Ha J. H.

Materials Science Poland

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2016

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Vol. 34, No. 3

487--493

EN

Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB) method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm-3, 9.94 × 1019 cm-3 and 1.99 × 1020 cm-3) and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot). It was shown that Cl dopant suppressed the unwanted secondary (5 1 1) crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm-3was above 1010cm.

7

Raman spectroscopy of CdTe/ZnTe quantum dot structures

Zielony E, Placzek-Popko E, Kamyczek P, Henrykowski A, Karczewski G

Optica Applicata

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2013

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Vol. 43, nr 1

181--185

EN

Semiconductor low-dimensional structures of CdTe quantum dots (QDs) embedded in ZnTe matrix have been investigated by micro-Raman spectroscopy. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by a molecular beam epitaxy technique on the p-type GaAs substrate. The Raman measurements have been performed at room temperature. The samples were excited by an Ar2+ laser of 514.5 nm wavelength. The Raman spectra have been recorded for different acquisition parameters of the measurement. For the reference and QD sample localized longitudinal (LO) phonons of 210 cm–1 wavenumber associated with the ZnTe layer are observed. In the case of QD sample another broadband corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm–1. Such behaviour does not exhibit the Raman spectra of the reference sample. Thus the Raman measurements confirm the presence of CdTe layer of quantum dots in the investigated material. Additionally, Raman spectra for both samples exhibit tellurium-related peaks at wavenumbers around 120 cm–1 and 140 cm–1, significantly increasing with laser time exposure. It is shown that the peaks are associated with the formation of Te aggregates on the ZnTe surface due to the laser damage in the ZnTe layer.

8

Osadzanie warstw CdTe na podłożach GaAs metodą rozpylania katodowego

Madejczyk P., Gawron W.

Biuletyn Wojskowej Akademii Technicznej

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2011

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Vol. 60, nr 2

313-320

PL

W pracy przedstawiono wyniki eksperymentów zmierzających do otrzymania warstw buforowych CdTe na podłożach GaAs. Chropowatość próbek z udanych eksperymentów zawiera się w przedziale 30-40 nm, co wstępnie kwalifikuje te warstwy do dalszych eksperymentów w systemie MOC VD. Uzyskano również dostateczną jednorodność grubości osadzonej warstwy CdTe na całej powierzchni podłoża GaAs. Badania struktury krystalograficznej otrzymanych warstw wykazały istnienie dwóch orientacji (100) i (111), co sugeruje, że otrzymane warstwy nie są monokrystaliczne.

EN

In this report, the results of CdTe buffer layers deposition on GaAs substrates by RF sputtering are presented. Surface roughness of CdTe layers was in the range from 30 nm to 40 nm. These CdTe layers are promising material as buffer layers for HgCdTe deposition in MOC VD technology. Sufficient thickness uniformity has been achieved on the whole surface of GaAs substrate. X-ray measurements show that deposited CdTe layers have two crystallographic orientations: (100) and (111) what suggest that those layers are not monocrystallic ones.

9

SXDR64 – Multichannel low noise ASIC for CdTe and GaAs detectors

Kachel M.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 11a

248-250

EN

A 64–channel ASIC called SXDR64 has been developed. The ASIC is aimed to work with DC coupled CdTe and GaAs detectors. Each channel of ASIC consists of charge sensitive amplifier, pole-zero cancellation circuit, 4th order shaper with programmable gain and peaking time from 115 ns to 380 ns, base-line restorer, two independent discriminators and two 20-bit counters. Simulated equivalent noise charge of the frontend electronics for 3 pF detector capacitance, detector leakage current of 500 pA and peaking time Tp = 380 ns is 123 electrons rms.

PL

SXDR64 jest 64-kanałowym układem scalonym przeznaczonym do odczytu sygnałów z detektorów CdTe oraz GaAs promieniowania X. Każdy kanał w układzie składa się ze wzmacniacza ładunkowego, układu kompensacji biegun-zero, układu kształtującego 4 stopnia, układu przywracania poziomu stałego, dwóch niezależnych dyskryminatorów oraz dwóch 20-bitowych liczników. Szumy oszacowane z symulacji wynoszą 123 el. rms, przy pojemności detektora 3p, prądzie upływu 0.5 nA.

10

Capacitance-voltage characteristics of MIS-structures on the basis of graded-band MBE Hg₁₋xCdxTe at passivation by epitaxially grown in situ CdTe

Voitsekhovskii A. V., Nesmelov S. N., Dzyadukh S. M., Varavin V. S., Dvoretskii S. A., Mikhailov N. N., Sidorov Y. G., Yakushev M. V.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

263-266

EN

The electrical properties of the interface between Hg₁₋xCdxTe (x = 0.22 and x = 0.32-0.36) and CdTe prepared in situ molecular beam epitaxy were estimated at 77 K. The methods of determination of main parameters of interface semiconductor/insulator and insulator from capacitance-voltage characteristics of MIS-structures based on graded-band Hg₁₋xCxTe have been developed. The fixed charge states density, fast surface states density, and density of mobile charge are obtained from capacitance-voltage measurements. For improvement in stable and electrical strength of insulator coating for several samples over CdTe additional protective layers SiO₂-Si₃N₄ are formed for x = 0.22 and ZnTe for x = 0.32-0.36.

11

High speed signal processing for photon counting X-ray detection

Shinomiya B., Koike A., Morii H., Okunoyama T., Neo Y., Mimura H., Aoki T.

Journal of Automation Mobile Robotics and Intelligent Systems

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2009

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Vol. 3, No. 4

143-146

EN

Recently practical X-ray measurement systems are demanded energy distinction function. Photon-counting CdTe semiconductor detectors have a high energy resolution in a low count rate condition at room temperature. However, the energy resolution is decreased by pile-up phenomenon in a high count rate condition. In conventional signal processing, processing time estimated X-ray photon energy from the pulse waveform is about tens of microseconds. This time is depended on the pulse decay time. This paper purposes to maintain the high energy resolution by changing the signal-processing algorithm, which derived the pulse rise height of the output waveform from the CdTe detector in a high count rate condition. As a result, the pulse rise time required to estimate the pulse rise height was short about 100 ns at incident X-ray energy 60 keV. As the result of energy spectrum by using this data, the FWHM of about 11keV (at 60 keV) when the count rate of 500 kcps. This result shows the possibility that the photon counting sensor has application for the high count rate imaging without decrease of the high energy resolution.

12

Evidence for metastable behavior of Ga-doped CdTe

Płaczek-Popko E., Gumienny Z., Trzmiel J., Szatkowski J.

Optica Applicata

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2008

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Vol. 38, nr 3

559-565

EN

In this paper, we report for the first time on persistent photoeffects in gallium doped CdTe. Persistent photoconductivity and photoinduced persistent absorption were observed at 77 K. Both effects quenched above 120 K. The photoeffects have been attributed to the metastable behavior of gallium in CdTe.

13

Performence of multichannel FX chip with DC Coupled Schottky CdTe detector

Kachel M.

Electronics and Telecommunications Quarterly

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2008

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Vol. 54, No 4

483-492

EN

This paper describes the performance of multichannel ASIC (called FX) which has been connected to Schottky CdTe detector by DC coupling. Because of DC coupling, leakage current of the detector flows into readout electronics and changes its performance. The I-V characteristic of CdTe Schottky detector with guard ring have been measured and we have performed both simulation and experimental verification of FX IC behavior vs. detector leakage current. Due to the low values of this detector leakage current (140 pA for bias voltage of 700 V) performance of FX IC is slightly influenced. Measurements performed with low values of detector's leakage current (below 1 nA), show that the gain of readout channel stays constant with changes of leakage current, while the offset voltage at the discrimonator input changes linearly of about 4.5 mV per 100 pA of the detector leakage current. Limitations of DC coupling method are shown based on measurements with Schottky CdTe detector without guard ring, which produces higer leakage current.

14

Reverse-bias DLTS for investigation of the interface region in thin film solar cells

Igalson M., Zabierowski P., Romeo A., Stolt L.

Opto-Electronics Review

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2000

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Vol. 8, No. 4

346-349

EN

The interface states in TCO/Cds/CdTe and ZnO/CdS/Cu(In,Ga)Se₂ photovoltaic devices has been studied by use of reverse-bias transient capacitance spectroscopy. Laplace transform analysis has been used in order to enhance a spectral resolution of the technique. It is shown that the method yields useful information on the electronic characteristics of the heterointerface in the thin film solar cells. The conclusion include a degree of inversion of the heterointerface and a contribution of tunneling in the carrier transport. The influence of these factors on photovoltaic performance of the devices under study is discussed.

15

Electrical characterisation of CdTe/CdS photovoltaic devices

Wimbor M., Romeo A., Igalson M.

Opto-Electronics Review

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2000

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Vol. 8, No. 4

375-377

EN

Thin film solar cells based on Cd/Te/Cds are expected to become the base material for the low - cost and efficient large-scale solar energy conversion devices. The samples have been investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements in order to define the transport mechanism in heterostructure and basic electronic parameters. Trap-assisted tunnelling has been found to dominate carrier transport mechanism in the junction.

16

Surface strain during homoepitaxy : growth and ion ablation of CdTe

Tatarenko S., Etgens V. H., Hartmann J. M., Martrou D., Arnoult A., Cibert J., Magnea N., Sauvage-Simkin M., Alvarez J., Ferrer S.

Opto-Electronics Review

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1999

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Vol. 7, No. 2

75-80

EN

Oscillations of the surface lattice parameter were observed by RHEED during the homoepitaxial growth of (001) CdTe by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE). The oscillations are associated to a deformation, induced by the surface reconstruction, at the free edges of the small 2D islands formed during the growth. In the same way, a lateral relaxation is measured during the layer by layer "de-growth" of (001) CdTe. Experiments using a CCD X-ray sensitive camera combined with the very bright X-ray beam offered by the European Synchrotron Radiation Facility allowed us to investigate the two layers behaviour of the CdTe surface in real time during the ablation by ion sputtering. The results show a relaxation mechanism, which is effective only whem islands are presented on the surface. A correlation has been found between the size the islands, their distribution, and the surface reconstruction. Particularly, a long-distance correlation between islands along the [1-10] direction has been observed.