83 research outputs found
Influence of an Sb doping layer in CIGS thin-film solar cells: a photoluminescence study
Sb doping of Cu(In,Ga)Se2 (CIGS) solar cells has been reported to exhibit a positive effect on the morphology of the absorber layer, offering a possibility to lower manufacturing cost by lowering the annealing temperatures during the CIGS deposition. In this work electron microscopy, energy-dispersive x-ray spectroscopy and photoluminescence experiments have been performed on cells deposited on soda-lime glass substrates, adding a thin Sb layer onto the Mo back contact prior to the CIGS absorber deposition. The defect structure of CIGS solar cells doped with Sb in this way has been investigated and is compared with that of undoped reference cells. The influence of substrate temperature during absorber growth has also been evaluated. For all samples the photoluminescence results can be explained by considering three donorâacceptor pair recombination processes involving the same defect pairs
Revealing trap depth distributions in persistent phosphors with a thermal barrier for charging
The performance of persistent phosphors under given charging and working
condition is determined by the properties of the traps that are responsible for
these unique properties. Traps are characterized by the depth of their
associated thermal barrier and a continuous distribution of trap depths is
often found in real materials. Accurately determining trap depth distributions
is hence of importance for the understanding and development of persistent
phosphors. However, extracting the trap depth distribution is often hindered by
the presence of a thermal barrier for charging, which causes a
temperature-dependent filling of traps. For this case, we propose a method for
extracting the trap depth distribution from a set thermoluminescence glow
curves obtained for variable charging temperature. The glow curves are
transformed into electron population functions via the Tikhonov regularization
in the framework of first-order kinetics. Subsequently, the evolution of the
occupation of the traps as a function of trap depth, quantified by the
so-called filling function, is obtained. Finally, the underlying trap depth
distribution can be reconstructed by two proposed methods. The proposed method
provides good precision and resolution for the trap depth distribution, which
is a step forward in acquiring a deeper understanding of the (de)trapping
behavior of persistent and storage phosphors.Comment: 15 pages, 11 figures; supplemental materials: 7 pages, 6 figure
Feature issue introduction: Persistent and photostimulable phosphors - an established research field with clear challenges ahead
Persistent phosphors have the ability to emit light long after the excitation has ended, typically by using thermal energy to liberate previously trapped charges. Alternatively, also photons can be used for the detrapping, leading to optically stimulated luminescence (OSL). This particular field of phosphor research has seen a strong expansion over the past two decades, with a steady growth of the materials library, an improved structural and luminescence characterization and the development of novel applications. Despite this success, clear challenges lie ahead in terms of a deeper understanding of the trapping mechanism and an associated optimization of the energy storage capacity being crucial for many applications. This focus issue âPersistent and Photostimulable Phosphorsâ within Optical Materials Express features papers presented at the third International Workshop on Persistent and Photostimulable Phosphors (IWPPP 2015) held at the University of Texas at Arlington
Optimizing the Mechanoluminescent Properties of CaZnOS:Tb via Microwave-Assisted Synthesis: A Comparative Study with Conventional Thermal Methods
Recent developments in lighting and display technologies have led to an increased focus on materials and phosphors with high efficiency, chemical stability, and eco-friendliness. Mechanoluminescence (ML) is a promising technology for new lighting devices, specifically in pressure sensors and displays. CaZnOS has been identified as an efficient ML material, with potential applications as a stress sensor. This study focuses on optimizing the mechanoluminescent properties of CaZnOS:Tb through microwave-assisted synthesis. We successfully synthesized CaZnOS doped with Tb3+ using this method and compared it with samples obtained through conventional solid-state methods. We analyzed the material's characteristics using various techniques to investigate their structural, morphological, and optical properties. We then studied the material's mechanoluminescent properties through single impacts with varying energies. Our results show that materials synthesized through microwave methods exhibit similar optical and, primarily, mechanoluminescent properties, making them suitable for use in photonics applications. The comparison of the microwave and conventional solid-state synthesis methods highlights the potential of microwave-assisted methods to optimize the properties of mechanoluminescent materials for practical applications
Europium doped thiosilicate phosphors of the alkaline earth metals Mg, Ca, Sr and Ba: Structure and luminescence
Effect of cation vacancies on the crystal structure and luminescent properties of Ca 0.85â1.5x Gd x Eu 0.1 ⥠0.05+0.5x WO 4 (0 †x  â€Â 0.567) scheelite-based red phosphors
KEu(MoO4)(2): Polymorphism, Structures, and Luminescent Properties
In this paper, with the example of two different polymorphs of KEu(MoO4)(2), the influence of the ordering of the A-cations on the luminescent properties in scheelite related compounds (A',A '') [(B',B '')O-4](m) is investigated. The polymorphs were synthesized using a solid state method. The study confirmed the existence of only two polymorphic forms at annealing temperature range 923-1203 K and ambient pressure: a low temperature anorthic alpha-phase and a monoclinic high temperature beta-phase with an incommensurately modulated structure. The structures of both polymorphs were solved using transmission electron microscopy and refined from synchrotron powder X-ray diffraction data. The monoclinic beta-KEu(MoO4)(2) has a (3+1)-dimensional incommensurately modulated structure (superspace group I2/b(alpha beta 0)00, a = 5.52645(4) angstrom, b = 5.28277(4) angstrom, c = 11.73797(8) angstrom, gamma = 91.2189(4)degrees, q = 0.56821(2)a*-0.12388(3)b*), whereas the anorthic alpha-phase is (3+1)-dimensional commensurately modulated (superspace group I (1) over bar(alpha beta gamma)0, a = 5.58727(22) angstrom, b = 5.29188(18)angstrom, c = 11.7120(4) angstrom, alpha = 90.485(3)degrees, beta = 88.074(3)degrees, gamma = 91.0270(23)degrees, q = 1/2a* + 1/2c*). In both cases the modulation arises due to Eu/K cation ordering at the A site: the formation of a 2-dimensional Eu3+ network is characteristic for the alpha-phase, while a 3-dimensional Eu3+-framework is observed for the beta-phase structure. The luminescent properties of KEu(MoO4)(2) samples prepared under different annealing conditions were measured, and the relation between their optical properties and their structures is discussed
Optical and structural properties of aluminium oxide thin films prepared by a non-aqueous solâgel technique
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