Wyniki wyszukiwania - Biblioteka Nauki

1

PbS nanopowder – synthesis, characterization and antimicrobial activity

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Suganya M. , Balu A. R.

Materials Science Poland

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2017

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tom Vol. 35, No. 2

322--328

EN

Lead sulphide (PbS) nanopowder was synthesized by a simple soft chemical route using lead nitrate and thiourea as precursor salts. The as-synthesized nanopowder was characterized by XRD, SEM, EDX, FT-IR, PL, Raman and magnetic measurements. XRD studies reveal the polycrystalline nature of the powder. The powder exhibits face-centered cubic structure with a strong (2 0 0) preferential orientation. The presence of Pb and S in the powder is confirmed by energy dispersive X-ray analysis. The peaks observed at 1112 cm-1 and at 606 cm-1 in the FT-IR spectrum are related to heteropolar diatomic molecules of PbS. The Raman peak shift at 173 cm-1 might have originated from the combination of longitudinal and transverse acoustic phonon modes associated with PbS crystal. The M-H loop confirms the paramagnetic nature of the as-synthesized PbS nanopowder. The nanopowder has significant antimicrobial activity against certain bacteria and fungi strains which make it suitable as antimicrobial agent against pathogenic microorganisms.

2

Signal processing for time resolved photoluminescence spectroscopy

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Grodecki K. , Murawski K. , Rutkowski J. , Kowalewski A. , Sobieski J.

Opto-Electronics Review

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2021

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tom Vol. 29, No. 3

91--96

EN

Accurate determination of material parameters, such as carrier lifetimes and defect activation energy, is a significant problem in the technology of infrared detectors. Among many different techniques, using the time resolved photoluminescence spectroscopy allows to determine the narrow energy gap materials, as well as their time dynamics. In this technique, it is possible to observe time dynamics of all processes in the measured sample as in a streak camera. In this article, the signal processing for the above technique for Hg1-xCdxTe with a composition x of about 0.3 which plays an extremely important role in the mid-infrared is presented. Machine learning algorithms based on the independent components analysis were used to determine components of the analyzed data series. Two different filtering techniques were investigated. In the article, it is shown how to reduce noise using the independent components analysis and what are the advantages, as well as disadvantages, of selected methods of the independent components analysis filtering. The proposed method might allow to distinguish, based on the analysis of photoluminescence spectra, the location of typical defect levels in HgCdTe described in the literature.

3

Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

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Wang F. F. , Yan B.

Materials Science Poland

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2013

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tom Vol. 31, No. 1

108-114

EN

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.

4

Photoluminescence of HgCdTe nanostructures grown by molecular beam epitaxy on GaAs

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Izhnin I. I. , Izhnin A. I. , Mynbaev K. D. , Bazhenov N. L. , Shilyaev A. V. , Mikhailov N. N. , Varavin V. S. , Dvoretsky S. A. , Fitsych O. I. , Voitsekhovsky A. V.

Opto-Electronics Review

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2013

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tom Vol. 21, No. 4

390-394

EN

Photoluminescence (PL) of HgCdTe-based hetero-epitaxial nanostructures with 50 to 1100 nm-wide potential wells was studied. The nanostructures were grown by molecular beam epitaxy on GaAs substrates. A strong degree of alloy disorder was found in the material, which led to the broadening of the PL spectra and a considerable Stokes shift that could be traced up to temperature T~230 K. Annealing of the structures improved the ordering and led to the increase in the PL intensity. A remarkable feature of the PL was an unexpectedly small decrease of its intensity with temperature increasing from 84 to 300 K. This effect can be related to localization of carriers at potential fluctuations and to the specific character of Auger-type processes in HgCdTe-based nanostructures.

5

Growth, structural and optical properties of novel nonlinear optical potassium phthalate di lithium borate (KPDLiB) single crystals

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Mohanraj K. , Balasubramanian D. , Jhansi N.

Materials Science Poland

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2020

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tom Vol. 38, No. 2

214--218

EN

Novel nonlinear optical semi-organic, potassium phthalate di lithium borate (KPDLiB) single crystals were successfully grown by the slow solvent evaporation technique. Good crystalline nature and an orthorhombic structure were confirmed by powder X-ray diffraction and single crystal X-ray diffraction studies. The functional groups of KPDLiB were identified using FT-IR spectrum recorded in the range of 4000 cm-1 to 450 cm-1. UV-Vis spectrum showed transmitting ability of the crystals in the entire visible region. The photoluminescence spectrum exhibited good fluorescence emission in a visible region at 384 nm, 416 nm and 578 nm. The second harmonic generation efficiency of the grown crystal was evaluated from Kurtz powder technique.

6

Carrier recombination in sonochemically synthesized ZnO powders

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Zakirov M. I. , Korotchenkov O. A.

Materials Science Poland

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2017

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tom Vol. 35, No. 1

211--216

EN

ZnO powders with particle size in the nm to μm range have been fabricated by sonochemical method, utilizing zinc acetate and sodium hydroxide as starting materials. Carrier recombination processes in the powders have been investigated using the photoluminescence, FT-IR and surface photovoltage techniques. It has been shown that the photoluminescence spectra exhibit a number of defect-related emission bands which are typically observed in ZnO lattice and which depend on the sonication time. It has been found that the increase of the stirring time results in a faster decay of the photovoltage transients for times shorter than approximately 5 ms. From the obtained data it has been concluded that the sonication modifies the complicated trapping dynamics from volume to surface defects, whereas the fabrication method itself offers a remarkably convenient means of modifying the relative content of the surface-to-volume defect ratio in powder grains and altering the dynamics of photoexcited carriers.

7

Photoluminescence spectroscopy for the evaluation of band potential roughness of InGaN active layers

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Kazlauskas K. , Jursenas S. , Miasojedovas S. , Pobedinskas P. , Tamulaitis G. , Zukauskas A. , Ivanov V. Y. , Godlewski M.

Optica Applicata

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2006

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tom Vol. 36, nr 2-3

181-185

EN

Photoluminescence spectroscopy in combination with Monte Carlo simulation of exciton hopping is demonstrated to be a valuable tool for quantitative analysis of the band potential profile in active layers for InGaN-based light emitters. Recently proposed double-scaled potential profile model is used to reveal the scale of potential fluctuations in the individual In-rich regions as well as the dispersion of the average exciton localization energy in these regions. The influence of the different potential fluctuation scales on the stimulated emission threshold and luminescence decay time of highly excited InGaN active layers is studied.

8

Photoluminescence and photoconductive characteristics of hydrothermally synthesized ZnO nanoparticles

100%

Mishra S. K. , Srivastava R. K. , Prakash S. G. , Yadav R. S. , Panday A. C.

Opto-Electronics Review

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2010

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tom Vol. 18, No. 4

467-473

EN

In the present paper, ZnO nanoparticles (NPs) with particle size of 20-50 nm have been synthesized by hydrothermal method. UV-visible absorption spectra of ZnO nanoparticles show absorption edge at 372 nm, which is blue-shifted as compared to bulk ZnO. Photoluminescence (PL) and photoconductive device characteristics, including field response, light intensity response, rise and decay time response, and spectral response have been studied systematically. The photoluminescence spectra of these ZnO nanoparticles exhibited different emission peaks at 396 nm, 416 nm, 445 nm, 481 nm, and 524 nm. The photoconductivity spectra of ZnO nanoparticles are studied in the UV-visible spectral region (366–691 nm). In spectral response curve of ZnO NPs, the wavelength dependence of the photocurrent is very close to the absorption and photoluminescence spectra. The photo generated current, Ipc = (Itotal - Idark) and dark current Idc varies according to the power law with the applied field IpcαVr and with the intensity of illumination Ipcα Vr, due to the defect related mechanism including both recombination centers and traps. The ZnO NPs is found to have deep trap of 0.96 eV, very close to green band emission. The photo and dark conductivities of ZnO NPs have been measured using thick film of powder without any binder.

9

Photoluminescence and Raman spectroscopies as an optical approach of stress determining in MOVPE grown quantum cascade laser structures

100%

Łozińska A. , Badura M. , Jadczak J. , Bielak K. , Ściana B.

Optica Applicata

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2020

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tom Vol. 50, nr 2

289--299

EN

In the presented work, an optical approach of stress determining in metalorganic vapor phase epitaxy (MOVPE) grown quantum cascade laser (QCL) structures was reported. In the case of such sophisticated structures containing hundreds of thin layers, it is important to minimize the stress generated in the QCL core. Techniques enabling determination of stress in such thin layers as those described in the article are photoluminescence and Raman spectroscopies. Based on Raman shift or changes in photoluminescence signal, it is possible to analyze stress occurring in the structure.

10

Luminescence based on energy transfer in xerogels doped with Tb2-xEux(WO4)3

100%

Grobelna B.

Optica Applicata

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2008

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tom Vol. 38, nr 1

39-47

EN

A series of luminescent materials consisting of Tb2-xEux (WO4)3 entrapped in silica xerogel were successfully prepared. The parameter x in the formula changed from 0.4 to 2. Spectroscopic properties such as absorption and luminescence of optically active ions were studied at room temperature. Owing to the energy transfer from the WO42- groups (ligand-metal charge transfer, (LMCT)) the lanthanide ions show their characteristic emissions in Tb2-xEux(WO4)3 entrapped in silica xerogel, i.e., 5D0 › 7FJ (J = 0, 1, 2, 3, 4) transition for Eu3+ ion and 5D4 › 7FJ (J = 6, 5, 4, 3) transition for Tb3+ ion. The energy transfer is effective for the mixed tungstate salt Tb1.35Eu0.65(WO4)3 entrapped in silica xerogel. The Eu(III) emission intensity in the materials under study increases with an increase in the annealing temperature from 600 to 900 °C. This is due to the removal of the effective O -H quenchers from the coordination sphere of the Eu(III) ion.

11

The photoluminescent properties of CdS clusters of different size in porous glasses

100%

Rysiakiewicz-Pasek E. , Polańska J. , Gevelyuk S. A. , Doycho I. K. , Mak V. T. , Zhukov S. A.

Optica Applicata

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2008

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tom Vol. 38, nr 1

93-100

EN

CdS nanoclusters were formed in the porous glass matrix by sequential chemical deposition from liquid-vapor phase and their chemical content was investigated. The room temperature photoluminescence spectra of specimens excited with a 235 nm wavelength had typical narrow peaks at 400 nm. The peaks can be explained by quantum effects for charge carriers confined inside the small-size (radius of the order of several nanometers) clusters. At the same time the luminescence spectra of the same specimens, but excited with a xenon lamp at 77 K, had peaks at ~700 nm that approximately corresponded to the band gap of the crystalline CdS. The possibility of the crystallites existence follows from the size distribution of voids in the porous glass matrix and is confirmed by the X-ray spectra typical of the wurtzite structure. The peculiarities of the observed luminescence spectra are explained by the energetic diagram of CdS in the configurational space.

12

Study of Ho doped Ag2S thin films prepared by CBD method

100%

Yadu G. , Pateria M. A. , Deshmukh K.

Materials Science Poland

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2020

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tom Vol. 38, No. 1

206--213

EN

Ho doped Ag2S thin films were grown on the glass substrate by chemical bath deposition (CBD) method at room temperature. The bath contained aqueous solution of silver nitrate, thiourea, EDTA, ammonia and holmium nitrate. Silver nitrate was used as a silver (Ag+) ion source; thiourea as sulfur (S−) ion source, EDTA was a complexing agent while ammonia was used to maintain pH, Ho(NO3)3 was taken as a source of Ho ions. The optical absorption edge of undoped (pure) and Ho doped silver sulfide films was determined between 324 nm and 298 nm showing blue shift as compared to bulk Ag2S. Band gaps calculated from Tauc plot also showed an increase in values for doped samples. The increase in band gap indicates reduced particle size in the prepared Ho doped films. The photoluminescence emission peaks were observed at around 578 nm to 601 nm wavelength and excitation peaks were found at 351 nm to 294 nm for undoped and doped films. The SEM micrograph consists of globular ball type and flower type structures observed in the prepared films of Ho doped Ag2S.

13

Photoreflectance spectroscopy of thick GaN layers grown by hydride vapour phase epitaxy technique

100%

Syperek M. , Kudrawiec R. , Misiewicz J. , Korbutowicz R. , Paszkiewicz R. , Tłaczała M.

Optica Applicata

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2005

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tom Vol. 35, nr 3

529-535

EN

The room temperature photoreflectance (PR) spectroscopy was used to investigate thick GaN epitaxial layers. The GaN layers were grown by hydride vapour phase epitaxy (HVPE) technique and compared to thin GaN layer grown by metalorganic vapour phase epitaxy (MOVPE) technique on AlN buffer layer. We observed energy red shift of the PR resonance for HVPE GaN layers compared with MOVPE GaN layer. This blue shift is due to reduction of the strain in HVPE layer. In addition, weak PR features related to Franz-Keldysh oscillations (FKO) have been observed. The electric field determined from the FKO period is 28 and 71 kV/cm for MOVPE and HVPE layers, respectively.

14

Photoluminescence of poly(N-vinylcarbazole) thin films deposited by dip-coating technique

100%

Rębarz M. , Dalasiński P. , Bała W. , Łukasiak Z. , Wojdyła M. , Kreja L.

Optica Applicata

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2005

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tom Vol. 35, nr 3

407-412

EN

This paper is concerned with the photoluminescence (PL) study of poly(N-vinylcarbazole) (PVK) thin films deposited on the glass substrate by the dip-coating method. The PL spectra have been measured under steady state excitation (He-Cd laser, 325 nm) in the temperature range from 13 to 300 K. All the samples being studied exhibit strong luminescence in broad temperature range. The main emission PL peak has maximum at 410 nm and is attributed to the excimer emission of PVK. We have observed a small red-shift of this peak with an increase of temperature. In all the films under investigation the thermal quenching of PL has been noticed. This behaviour is determined by the closeness of carbazole groups belonging to neighbouring chains because the interaction between them leads to nonradiative transitions. The PL spectra of PVK thin films annealed under iodine atmosphere have also been investigated. We have observed a decrease of PL for these films. We have concluded that the annealing of PVK under iodine atmosphere induces its degradation.

15

Photoluminescence characterization of vacuum deposited PTCDA thin films

100%

Bała W. , Łukasiak Z. , Rębarz M. , Dalasiński P. , Bratkowski A. , Bauman D. , Hertmanowski R.

Opto-Electronics Review

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2004

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tom Vol. 12, No. 4

445-448

EN

We investigated photoluminescence (PL) under steady state excitation and photoluminescence excitation (PLE) spectra of thin 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films deposited on (001)Si substrate with various layer thicknesses grown at different substrate temperatures. The PL and PLE spectra have been measured at various temperatures, ranging from 10 K to 325 K. The PTCDA films exhibit strong luminescence at all mentioned ranges of temperature and for different values of excitation energy. The vibronic structure of PL spectra is clearly resolved at different temperatures. The position of peaks on energy scale depends on the temperature. We have observed a blue-shift of peaks with the decrease in the temperature. In all the investigated samples, the thermal quenching of PL has been observed. Analysis of the temperature dependence of the intensity bands, their position and full width half maximum (FWHM) allowed to find the energy barriers between the excited state and defect state. We propose a schematic potential energy diagram which explains mechanism of PL recombination

16

Temperature dependence of Bi4Ge3O12 photoluminescence spectra

100%

Kaczmarek S. M. , Tsuboi T. , Nakai Y. , Berkowski M. , Huang W. , Kowalski Z.

Materials Science Poland

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2014

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tom Vol. 32, No. 1

7--11

EN

Bi4Ge3O12 single crystals were obtained using Czochralski growth method. Photoluminescence spectra were analyzed versus temperature from 12 to 295 K. Besides the previously observed emission bands at 610 and 820 nm, the new emission band at 475 nm was found by a careful temperature dependence measurement in the present study. The influence of basic and defect structure on the shape and position of the spectra versus temperature was discussed.

17

CdO-Fe3O4 nanocomposite with enhanced magnetic and photocatalytic properties

100%

Nallendran R. , Selvan G. , Balu A. R.

Materials Science Poland

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2019

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tom Vol. 37, No. 1

100--107

EN

Pure CdO nanopowder and CdO-Fe3O4 nanocomposite were synthesized by a cost effective chemical method, and the samples were characterized by XRD, SEM, TEM, FT-IR, UV-Vis-NIR and PL. Also, magnetic and photocatalytic properties of the synthesized samples were studied. XRD patterns of the composite confirm the presence of diffraction peaks related to both CdO and Fe3O4. EDX spectrum confirms the presence of the elements Cd, O and Fe in the composite. Peaks related to Cd–O and Fe–O bonds were observed respectively at 688 cm−1 and 592 cm−1 in the FT-IR spectrum. The paramagnetic behavior of pure CdO becomes ferromagnetic when coupled with Fe3O4. The composite exhibited a high photodegradation efficiency of 92.85 % against the degradation of methylene blue dye under visible light radiation.

18

Role of nitrogen in carrier confinement potential engineering and optical properties of GaAs-based quantum wells heterostructures

100%

Pucicki D. , Bielak K. , Dawidowski W. , Ściana B. , Tłaczała M.

Optica Applicata

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2016

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tom Vol. 46, nr 2

255--263

EN

In this work, the authors present the results of optical characterization of GaAs-based multiple quantum well heterostructures, together with energy band structure analysis. The optical properties were investigated by applying photoluminescence spectroscopy. Structures with GaInNAs, GaInAs and GaNAs multiple quantum wells emitting around 1 μm, grown by atmospheric pressure metalorganic vapor phase epitaxy, were compared in this work. The role of nitrogen in quantum well carriers confinement potential was analysed. The photoluminescence intensities of the samples were correlated with the analysis of energy band structures and the overlaps of the carriers’ wave functions. In addition, the main carrier activation energies were estimated based on photoluminescence temperature dependence and the Arrhenius plots analysis. It was deduced that the thermal photoluminescence decay is most probably related to the escape of electrons whereas the holes, independently of the potential well depth, are additionally confined by the local inhomogeneities or by the Coulomb interaction with the confined electrons.

19

Effect of Sm concentration on optical and electrical properties of CdSe nanocrystalline thin film

100%

Pathak K. K. , Pateria M. A. , Deshmukh K. , Jha P.

Materials Science Poland

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2019

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tom Vol. 37, No. 1

33--38

EN

Present paper reports optical and electrical properties of samarium doped CdSe nanocrystalline thin film which was grown on a glass substrate by chemical bath deposition method (CBD). X-ray diffraction (XRD) analysis revealed that the deposited films were nanocrystalline with sphalerite cubic structure. The average crystallite size calculated from FWHM of XRD peaks was found to be 10.11 nm. The bandgap of the Sm doped CdSe nanocrystalline thin films was calculated to be 1.91 eV to 2.22 eV. The optical absorption edge of undoped (pure) and Sm doped CdSe films was obtained between 650 nm to 640 nm showing blue shift as compared to bulk CdSe. Sm doping further enhanced the photoconductivity of these films. The I-V characteristic confirmed the suitability of prepared films for photosensor applications.

20

Photoluminescence study of ZnO/CdS/Cu(In,Ga)Se2 solar cells

100%

Bacewicz R. , Żuk P. , Trykozko R.

Opto-Electronics Review

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2003

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tom Vol. 11, No. 4

277-280

EN

Photoluminescence (PL) of the absorber layer of ZnO/CdS/Cu(In,Ga)Se2 solar cells has been studied. Baseline process solar cells as well as structures subject to a damp heat treatment and sodium - free structures have been investigated. The excitation intensity and temperature dependence of the photoluminescence spectra have been measured. A large blue shift of the photoluminescence bands for increasing excitation intensity has been observed with a per decade shift value ranging from 10 meV for baseline cells to 35 meV for Na free cells. This is characteristic behaviour for spectral bands due to transitions involving random potential fluctuations in highly compensated In-rich near-interface layer of the Cu(In,Ga)Se2 film. The temperature evolution of the spectra indicates two types of PL transitions: the tail-impurity and band-impurity transitions. The change of the PL spectra upon the damp heat treatment is discussed.