Lidé

Ing. Lucie Landová

Všechny publikace

Influence of Mo doping on the luminescence properties and defect states in ZnO nanorods. Comparison with ZnO:Mo thin films

  • Autoři: Buryi, M., Remeš, Z., Babin, V., Novotný, M., Ing. Lucie Landová,
  • Publikace: Applied Surface Science. 2021, 555 ISSN 0169-4332.
  • Rok: 2021
  • DOI: 10.1016/j.apsusc.2021.149679
  • Odkaz: https://doi.org/10.1016/j.apsusc.2021.149679
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    ZnO:Mo powders of nano- and microrods were fabricated by the hydrothermal growth method. ZnO:Mo thin films deposited on a fused silica glass substrate. The samples were also annealed in air at elevated temperatures to study the defects and luminescence modification. In particular, EPR spectra in the powder and thin film samples were composed of the signals originating from shallow donors before any treatment. The Mo5+ signal appeared after the annealing at 350 ◦C in the powder spectra. It existed prior to the treatment in the thin film samples. New EPR signal appears after X-ray irradiation in the powder samples. Red luminescence occurs in all powder samples. It depends on the annealing temperatures and Mo content. The exciton-related band at 380 nm never observed in the powder samples before the annealing, appears after the annealing at 350 ◦C. The strongest it was in the ZnO:Mo powder with low Mo content.

Pulsed laser deposition of high-transparency molybdenum oxide thin films

  • DOI: 10.1016/j.vacuum.2021.110613
  • Odkaz: https://doi.org/10.1016/j.vacuum.2021.110613
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Molybdenum oxide is an intensively studied material, thanks to its high bandgap, high work function, and potentially also photochromism, plasmonic properties, and layered structure. In this contribution, we employ Pulsed Laser Deposition (PLD) from stoichiometric MoO3 and metal Mo target at temperature range of 25 °C – 500 °C and oxygen pressure variation of 0.1 mbar – 0.4 mbar to deposit high transparency MoO3 layers. The combination of Photothermal Manuscript File Click here to view linked ReferencesDeflection Spectroscopy (PDS) and Spectral Ellipsometry is applied to accurately track all the optical properties. The X-ray diffraction and Scanning Electron Microscopy (SEM) are used to monitor crystallinity and surface morphology.

Stabilization of light emitting Eu2+ centers inside Ca(Sr)I-2:Eu particles in glass ceramics. The preliminary concept of synthesis

  • Autoři: Buryi, M., Salamakha, T., Babin, V., Páterek, J., Hájek, F., Ing. Lucie Landová,
  • Publikace: Ceramics International. 2021, 47(20), 29232-29252. ISSN 0272-8842.
  • Rok: 2021
  • DOI: 10.1016/j.ceramint.2021.07.088
  • Odkaz: https://doi.org/10.1016/j.ceramint.2021.07.088
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Glass ceramics in the form of MI2 :Eu crystalline particles grown in MO-B2O3 glass (M = Ca, Sr, Ba) through recrystallization from the alloyed melt were fabricated. Eu2+ ions were detected in the CaI2 and SrI2 crystalline particles (not in the BaI2) inside the corresponding glasses. Some amount of Eu2+ centers are expected to originate from the MO-B2O3 glass hosts as well. This was confirmed by correlated electron paramagnetic resonance (EPR), photo- and radioluminescence (PL, RL) measurements. Peculiarities of the Eu2+ distribution and incorporation into the glass ceramics samples as well as charge and energy transfer properties are discussed in detail. Optimal conditions leading to the enhancement of the Eu2+ emission from the CaI2 and SrI2 crystallites inside the glasses were determined.

Transformation of free-standing ZnO nanorods upon Er doping

  • Autoři: Buryi, M., Remeš, Z., Babin, V., Artemenko, A., Ing. Lucie Landová,
  • Publikace: Applied Surface Science. 2021, 562 ISSN 0169-4332.
  • Rok: 2021
  • DOI: 10.1016/j.apsusc.2021.150217
  • Odkaz: https://doi.org/10.1016/j.apsusc.2021.150217
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Erbium doped zinc oxide (ZnO:Er) powder was synthesized by hydrothermal growth. The morphology changed from undoped nanorods to microrods. The effect of Er doping on luminescence properties of ZnO:Er was observed. Furthermore, annealing in air at elevated temperatures up to 700 ◦C results in additional modification of defect states and related luminescence properties.

Unveiling the Effect of Potassium Treatment on the Mesoporous TiO2/ Perovskite Interface in Perovskite Solar Cells

  • DOI: 10.1021/acsaem.1c02229
  • Odkaz: https://doi.org/10.1021/acsaem.1c02229
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    A method for improving mesoporous TiO2/perovskite interfacial characteristics in perovskite solar cells (PSCs) is demonstrated by modifying mesoporous TiO2 with potassium (K) treatment. It is found that the modification of mesoporous TiO2 with K treatment enhances the perovskite crystallization process, producing a perovskite film with higher crystallinity and larger grains. K treatment passivates trap sites in mesoporous TiO2 and reduces sub-band-gap deep defect states at the interface of the perovskite, thereby suppressing the nonradiative recombination and improving Voc of PSCs. Stronger photoluminescence quenching and shorter carrier lifetime are also observed for the perovskite on K-treated mesoporous TiO2, indicating more efficient charge collection across the interface. As a result of these advancements, PSC based on K-treated mesoporous TiO2 shows a high power conversion efficiency of 20.60% compared to PSC without K treatment and improves the environmental stability in air

Controlled Growth of Large Grains in CH3NH3PbI3 Perovskite Films Mediated by an Intermediate Liquid Phase without an Antisolvent for Efficient Solar Cells

  • DOI: 10.1021/acsaem.0c02441
  • Odkaz: https://doi.org/10.1021/acsaem.0c02441
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Crystalline large grains with uniform morphologies of the perovskite films are important for achieving stable, high-performance perovskite solar cells. Herein, a strategy to control the growth of grains in CH3NH3PbI3 films is demonstrated by modifying the perovskite film deposition process through forming an intermediate CH3NH3PbI3·methylammonium chloride (MACl)·xCH3NH2 liquid phase induced by CH3NH2 gas treatment in combination with MACl additive. By tuning the incorporation of MACl additive to the perovskite precursor solution, this intermediate phase enables the controlled growth of grains up to 3 μm, uniform morphology, and high crystallinity in the films. The high-quality CH3NH3PbI3 film leads to enhanced carrier lifetime and reduced charge-trap density and nonradiative recombination of perovskite films. Solar cells made via CH3NH3PbI3·MACl·xCH3NH2 phase exhibit high power conversion efficiency of 18.4%, higher than solar cells made without MACl (15.8%).

Elucidating the role of TiCl(4)post-treatment on percolation of TiO(2)electron transport layer in perovskite solar cells

  • DOI: 10.1088/1361-6463/ab938c
  • Odkaz: https://doi.org/10.1088/1361-6463/ab938c
  • Pracoviště: Katedra elektrotechnologie, Katedra řídicí techniky
  • Anotace:
    The ideal electron transport layer of a high performance perovskite solar cell should have good optical transparency, high electron mobility, and an energy level alignment well-matched with the perovskite material. In this work, we investigate the role of TiCl(4)post-treatment of the mesoporous TiO(2)electron transport layer by varying the concentration of TiCl(4)and characterizing optical and electrical properties, charge carrier dynamics, and photovoltaic performance of mesoscopic CH(3)NH(3)PbI(3)solar cells. It is found that the TiCl(4)treatment provides an additional interconnection between the TiO(2)particles, leading to better percolation as evident from high resolution cross-section images and chemical maps. This enhances effective electron mobility in the material as well as significantly reduces average sub-bandgap absorption due to defects and electronic disorder determined by photothermal deflection spectroscopy.

Impact of Cation Multiplicity on Halide Perovskite Defect Densities and Solar Cell Voltages

  • Autoři: Ledinský, M., Vlk, A., Schönfeldová, T., doc. Mgr. Jakub Holovský, Ph.D., Aydin, E., Dang, H.X., Hájková, Z., Ing. Lucie Landová, Valenta, J., Fejfar, A., De Wolf, S.
  • Publikace: Journal of Physical Chemistry C. 2020, 124(50), 27333-27339. ISSN 1932-7447.
  • Rok: 2020
  • DOI: 10.1021/acs.jpcc.0c08193
  • Odkaz: https://doi.org/10.1021/acs.jpcc.0c08193
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Metal-halide perovskites feature very low deep-defect densities, thereby enabling high operating voltages at the solar cell level. Here, by precise extraction of their absorption spectra, we find that the low deep-defect density is unaffected when cations such as Cs+ and Rb+ are added during the perovskite synthesis. By comparing single crystals and polycrystalline thin films of methylammonium lead iodide/bromide, we find these defects to be predominantly localized at surfaces and grain boundaries. Furthermore, generally, for the most important photovoltaic materials, we demonstrate a strong correlation between their Urbach energy and open-circuit voltage deficiency at the solar cell level. Through external quantum yield photoluminescence efficiency measurements, we explain these results as a consequence of nonradiative open-circuit voltage losses in the solar cell. Finally, we define practical power conversion efficiency limits of solar cells by taking into account the Urbach energy

Optical characterization of low temperature amorphous MoOx, WOX, and VOx prepared by pulsed laser deposition

  • DOI: 10.1016/j.tsf.2019.137690
  • Odkaz: https://doi.org/10.1016/j.tsf.2019.137690
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Transition metal oxides are materials combining properties of electrical conductivity, optical transparency, and catalytical function. They are widely used in applications including solar cells, flat panel displays, and detectors. In particular, high work function oxides such as MoO3, WO3, and V2O5 have become popular. In many applications, low deposition temperatures are required, leading to amorphous structure. In this study, thin films of amorphous MoOX, WOX, and VOX were prepared by pulsed laser deposition, and their optical properties and work function were determined. Samples of polycrystalline ZnO were also prepared for comparison. Substrate temperature was varied in the range of 25 °C–100 °C and oxygen pressure was varied in the range of 10–20 Pa during the process. Effect of pressure during sample cool-down and chamber venting was also observed.. Optical characterization was based on photothermal deflection spectroscopy, which is a non-contact and non-destructive method for measuring directly absorptance spectra with sensitivity down to 10–4. Absorptance in the band gap serves as an indication of the presence of defects such as oxygen vacancies or metallic phases. Our optimized films achieved a sub-bandgap absorption coefficient as low as 103 cm−1 for MoOX, VOX, and 102 cm−1 in the case of the WOX. From the gradient of the absorption edge, Urbach energy was obtained, evaluating disorder in the semiconductor material. The work function of each material was obtained by Kelvin probe, and a slight correlation with Urbach energy was found. X-ray photoelectron spectroscopy indicated successful stochiometric transfer mainly for the lowest pressure and highest temperature samples.

Concentration-Dependent Impact of Alkali Li Metal Doped Mesoporous TiO2 Electron Transport Layer on the Performance of CH3NH3PbI3 Perovskite Solar Cells

  • DOI: 10.1021/acs.jpcc.9b05355
  • Odkaz: https://doi.org/10.1021/acs.jpcc.9b05355
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    TiO2 is commonly employed as an electron transport layer (ETL) in mesoscopic n−i−p perovskite solar cells (PSCs). However, the low electron mobility, low electrical conductivity, and high electronic trap states of TiO2 have negative impacts on further enhancement of PSC performance. Metal doping is an efficient way to improve the electronic properties of TiO2 films. In this work, we investigate the concentration-dependent impact of alkali lithium metal doping of the mesoporous TiO2 ETL on the performance of mesoscopic CH3NH3PbI3 PSCs. It was found that Li doping results in improvement in electrical conductivity and electron mobility and reduces the number of electronic trap states arising due to the oxygen vacancies within TiO2 lattice. The device performance relies on the concentration of Li doping, and the power conversion efficiency (PCE) of the PSC was improved from 13.64% to 17.59% for a Li doped mesoporous TiO2 layer with an optimized concentration of 30 mg/mL.

Deep levels, charge transport and mixed conductivity in organometallic halide perovskites

  • Autoři: Musiienko, A., Moravec, P., Grill, R., Ing. Lucie Landová,
  • Publikace: ENERGY & ENVIRONMENTAL SCIENCE. 2019, 12(4), 1413-1425. ISSN 1754-5692.
  • Rok: 2019
  • DOI: 10.1039/c9ee00311h
  • Odkaz: https://doi.org/10.1039/c9ee00311h
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Organometallic halide perovskites (OMHPs) have recently undergone a remarkable development as highly efficient optoelectronic materials for a variety of applications particularly solar cells, light emitting diodes and photodetectors. To fully use the potential of OMHPs, several important challenges must be overcome. One of these challenges is the understanding and control of their defect structures. The available data from multiple research studies suggest that trap-assisted recombination exists in OMHPs despite their large carrier lifetimes, which makes these materials highly attractive, and this has resulted in the perovskite boom over the last decade. Conventional spectroscopy faces serious obstacles in OMHPs due to their low defect concentrations and capture cross section, and therefore the electronic structure of such semiconductors remains poorly understood. By using highly specialized photo-Hall effect spectroscopy, we visualized the deep level defects responsible for non-radiative recombination and established their parameters in the MAPbBr3 perovskite. The presented deep level model in combination with Time of Flight measurements demonstrated that the electron transport is mostly affected by the trap-assisted recombination. Meanwhile, holes are only influenced by the partially filled deep level. The presented electrical and charge transport properties are crucial for informing the processing conditions towards the elimination of these defects as was done for classical inorganic semiconductors.

Lead Halide Residue as a Source of Light-Induced Reversible Defects in Hybrid Perovskite Layers and Solar Cells

  • DOI: 10.1021/acsenergylett.9b02080
  • Odkaz: https://doi.org/10.1021/acsenergylett.9b02080
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Advanced characterization methods avoiding transient effects in combination with solar cell performance monitoring reveal details of reversible light-induced perovskite degradation under vacuum. A clear signature of related deep defects in at least the 1 ppm range is observed by low absorptance photocurrent spectroscopy. An efficiency drop, together with deep defects, appears after minutes-long blue illumination and disappears after 1 h or more in the dark. Systematic comparison of perovskite materials prepared by different methods indicates that this behavior is caused by the lead halide residual phase inherently present in material prepared by the two-step method. X-ray photoelectron spectroscopy confirms that lead halide when illuminated decomposes into metallic lead and mobile iodine, which diffuses into the perovskite phase, likely producing interstitial defects. Single-step preparation, as well as preventing lead halide illumination, eliminates this effect.

Temperature Dependence of the Urbach Energy in Lead Iodide Perovskites

  • DOI: 10.1021/acs.jpclett.9b00138
  • Odkaz: https://doi.org/10.1021/acs.jpclett.9b00138
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    To gain insight into the properties of photovoltaic and light-emitting materials, detailed information about their optical absorption spectra is essential. Here, we elucidate the temperature dependence of such spectra for methylammonium lead iodide (CH3NH3PbI3), with specific attention to its sub-band gap absorption edge (often termed Urbach energy). On the basis of these data, we first find clear further evidence for the universality of the correlation between the Urbach energy and open-circuit voltage losses of solar cells. Second, we find that for CH3NH3PbI3 the static, temperature-independent, contribution of the Urbach energy is 3.8 ± 0.7 meV, which is smaller than that of crystalline silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN), underlining the remarkable optoelectronic properties of perovskites.

Improved Contactless Method of IR Reflectance under Grazing Incidence for Measurement of Doping Profiles

  • Autoři: doc. Mgr. Jakub Holovský, Ph.D., Remeš, Z., Franta, D., Conrad, B., Ing. Lucie Landová, Ing. David Bušek, Ph.D., Poruba, A.
  • Publikace: Proceedings of the International Conference of 35th European Photovoltaic Solar Energy Conference and Exhibition. München: WIP Wirtschaft und Infrastruktur GmbH & Co Planungs KG, 2018. p. 278-280. ISSN 2196-100X. ISBN 978-3-936338-50-8.
  • Rok: 2018
  • DOI: 10.4229/35thEUPVSEC20182018-2AO.5.3
  • Odkaz: https://doi.org/10.4229/35thEUPVSEC20182018-2AO.5.3
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    We have elaborated contactless method of measurement and evaluation of doping profiles in silicon polished wafers based on infrared reflectance under high angle of incidence. We have found higher angle of incidence increases sensitivity, however approaching Brewster angle increases also experimental error, therefore 65 angle has been chosen. Moreover, to increase reproducibility we divide the measured spectra by reference spectra taken on an undoped sample, and further we rescale the spectra to fixed value in the region of 4000 cm-1–7000 cm-1. To reduce number of evaluated parameter, the carrier profile in boron-doped samples was parametrized by 3 parameters and that in phosphorous-doped samples was parametrized by 4 parameters, using additional empirically determined assumption that the first part of the profile is a constant plateau and that the following two exponential tails are joined at a value of 3x10^19 cm-3.

Measurement of doping profiles by a contactless method of IR reflectance under grazing incidence

  • DOI: 10.1063/1.5015988
  • Odkaz: https://doi.org/10.1063/1.5015988
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    The grazing angle infrared reflectance method of the measurement and evaluation of charge carrier profiles in polished wafers was developed. Experimental errors were minimized by division by reference spectra taken on an undoped sample and further by normalization to a fixed value in the region of 4000/cm to 7000/cm. The carrier profile in boron-doped samples was parametrized by 3 parameters and that in phosphorous-doped samples was parametrized by 4 parameters, using additional empirically determined assumptions. As a physical model, the Drude equation is used with two parameters assumed to be concentration-dependent: relaxation time and contribution from band-to-band excitations. The model parameters were calibrated independently by infrared ellipsometry. The presented method gives results in satisfactory agreement with the profiles measured by the electrochemical capacitance-voltage method.

Perovskity – nový fenomén ve fotovoltaice

  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    Organicko-anorganické perovskity se nedávno ukázaly jako nadějný materiál pro výrobu levných tenkovrstvých slunečních článků s vysokou účinností. Příspěvek představuje strukturu perovskitů, jednoduché metody jejich přípravy a slibnou perspektivu tandemového slunečního článku perovskitu s křemíkem. Zmíněny jsou též dvě slabiny, které zatím brání komerční výrobě perovskitových slunečních článků.

Probing Photoinduced Degradation of CH3NH3PbI3 Perovskite Films by Kelvin Probe and Photoluminescence Techniques

  • DOI: 10.4229/35thEUPVSEC20182018-3DO.4.5
  • Odkaz: https://doi.org/10.4229/35thEUPVSEC20182018-3DO.4.5
  • Pracoviště: Katedra elektrotechnologie
  • Anotace:
    In this work, the photoinduced degradation of CH3NH3PbI3 perovskite films under illumination in ambient conditions (relative humidity 30-50%) was studied by Kelvin Probe and Photoluminescence techniques. Using Kelvin Probe techniques, we investigated the effects on the work function of the CH3NH3PbI3 film on fluorine-doped SnO2 (FTO) at various photoinduced degradation states in the dark and under illumination. It was found that the work function of CH3NH3PbI3 film on FTO was gradually increased in the dark after every 10 min illumination step until the film was completely degraded. The gradual increase in work function due to the degradation can be ascribed to modulation doping of the CH3NH3PbI3 by PbI2 phase. It was also found that the contact potential difference (CPD) of CH3NH3PbI3 on FTO was increased under illumination as a result of a positive surface photovoltage relative to the FTO.

Za stránku zodpovídá: Ing. Mgr. Radovan Suk