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The Influence of Metastabilities on the Luminescence in the Cu(In,Ga)Se_2 Solar Cells

100%
Prządo D., Igalson M., Bacewicz R., Edoff M.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
183-189
EN
Photoluminescence and electroluminescence spectra of the absorber layer in ZnO/CdS/Cu(In,Ga)Se_2 solar cells were measured. Their dependence on temperature, excitation intensity and applied voltage were studied. Electroluminescence measurements were used to investigate light- and bias-induced metastabilities in the absorber of the cells. We showed that metastable changes of defect distributions, which produce an effect on the electrical characteristics of ZnO/CdS/Cu(In,Ga)Se_2 material, affect also the luminescence yield. The dependence of the intensity and shape of the electroluminescence spectra on the state of the sample is observed. These results fit well into the theoretical calculations of Lany and Zunger model showing that divacancy complex (V_{Se}-V_{Cu}) is responsible for metastable changes observed in ZnO/CdS/Cu(In,Ga)Se_2-based solar cells. We conclude that during light soaking or/and forward bias the probability of nonradiative recombination is decreased.
2
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Local Structure Around Te in Heavily Doped GaAs:Te using X-Ray Absorption Fine Structure

88%
Pietnoczka A., Bacewicz R., Slupinski T., Antonowicz J., Wei S.-H.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
879-882
EN
The annealing of heavily doped GaAs:Te can significantly change the free electron concentration in a reversible manner. These changes of electrical properties are accompanied by the structural changes of GaAs:Te solid solution. We used X-ray Absorption Fine Structure at K-edge of tellurium to determine local changes around Te atoms for different states of the GaAs:Te crystals caused by the annealing corresponding to different electron concentrations. The best EXAFS fit for the samples with high electron concentration was obtained for the substitutional Te_{As} model with elongated Te-Ga bonds (as compared to the As-Ga distance). For the samples in the low concentration state the best fit was for the pairs of Te atoms forming a rhombohedral symmetry double-DX centre, with the proportional admixture of the substitutional tellurium
3
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Local Structure of Mn in (La_{1-x}Ho_{x})_{2/3}Ca_{1/3}MnO_{3} Studied by X-ray Absorption Fine Structure

64%
Pietnoczka A., Pękała M., Bacewicz R., Drozd V., Fagnard J., Vanderbemden P., Antonowicz J., Zalewski W.
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issue 2
281-285
EN
Results of X-ray absorption fine structure measurements in manganites (La_{1-x}Ho_{x})_{2/3}Ca_{1/3}MnO_{3} with 0.15 < x < 0.50 are presented. When LaMnO_{3} is doped with a divalent element such as Ca^{2+}, substituting for La^{3+}, holes are induced in the filled Mn d orbitals. This leads to a strong ferromagnetic coupling between Mn sites. Ca ions in La_{1-x}Ca_{x}MnO_{3} introduce a distortion of the crystal lattice and mixed valence Mn ions (Mn^{3+} and Mn^{4+}). On the other hand, in manganites (La_{1-x}Ho_{x})_{2/3}Ca_{1/3}MnO_{3} the substitution of La for Ho causes a lattice distortion and induces a disorder, which reduces a magnetic interaction. The ferromagnetic transition temperature and conductivity decrease very quickly with increasing x. The magnetic and transport properties of compounds depend on the local atomic structure around Mn ions. The information on the bond lengths and Debye-Waller factor are obtained from the extended X-ray absorption fine structure (EXAFS) data analysis. The charge state of Mn is determined from the position of the absorption edge in X-ray absorption near edge structure (XANES) data. XAFS results are in good agreement with magnetic characteristics of the studied materials.
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