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  • 1.
    Davydova, Alexandra
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Eriksson, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Chen, R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Persson, C.
    Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, NO-0316 Oslo, Norway;KTH Royal Inst Technol, Dept Mat Sci & Engn, S-10044 Stockholm, Sweden.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thio-olivine Mn2SiS4 thin films by reactive magnetron sputtering: Structural and optical properties with insights from first principles calculations2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 152, s. 110-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thio-olivines such as (Fe,Mn)(2)(Si,Ge)S-4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4 thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is observed, revealing the oxidation/hydrolysis of Si-S bonds from the as-deposited film as a blocking mechanism for the ternary compound formation. Structural, morphological and optical properties of the annealed Mn2SiS4 films are reported for the first time. Resulting Mn2SiS4 films have orthorhombic Pnma structure and are polycrystalline. Raman active modes at 325 nm excitation are observed at 262, 320, 400 and 464 cm(-1). From room temperature photoluminescence at 532 nm excitation the band gap is estimated to be about 1.9 eV, but a high optical absorption coefficient of > 10(4) cm(-1) was only obtained at E > 2.8 eV.First principles calculations are used for better understanding of opto-electronic properties. From the calculations, Mn2SiS4 is suggested to have a band gap of about 1.73-1.86 eV depending on the magnetic configuration of Mn and slight indirect nature. The slow absorption onset is interpreted by strong anisotropy due to one of the components of the dielectric function. 

  • 2.
    Davydova, Alexandra
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    The Single Phase Region in Cu2ZnSnS4 Thin Films from Theory and Combinatorial Experiments2018Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 14, s. 4624-4638Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu2ZnSnS4 (CZTS) is hoped to be a future, earth-abundant absorber material for thin film solar cells, but performance remains below the level needed for commercialization. In this work, the size of the single phase region of CZTS obtained from thin film synthesis methods is explored, to determine the scope available for defect engineering and thereby future improvements in solar cell performance. A chemical model for the single phase region is presented, based on equilibria between defect complexes in the CZTS phase and the other solid- and gas-phase components present during synthesis. The model predicts a variable single phase region size, depending on the partial pressures of SnS and S2. The model is verified by analysis of combinatorial thin-film CZTS samples prepared with different synthetic conditions and characterized by Raman and compositional mapping. We conclude that typical synthesis strategies for CZTS are not capable of accessing the full range of the CZTS single phase region since the required partial pressure of S2 is very large. The important implication is that our understanding of CZTS defect chemistry from experimental studies is incomplete and that scope exists for tuning the defect properties toward better solar cell performance.

  • 3.
    Li, Shu-Yi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Hagglund, Carl
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Ren, Yi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsen, Jes K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Frisk, Christopher
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Englund, Sven
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer-Bjorkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Optical properties of reactively sputtered Cu2ZnSnS4 solar absorbers determined by spectroscopic ellipsometry and spectrophotometry2016Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 149, s. 170-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have determined for the first time the device-relevant optical constants of 500 nm and 800 nm-thick Cu2ZnSnS4 absorbers, grown on bare and Mo-coated soda-lime glass (SLG), using spectroscopic ellipsometry (SE). The composition, structure, phase purity and morphology were characterized by X-ray fluorescence, X-ray photoelectron spectroscopy depth profiling, X-ray diffraction, Raman spectroscopy, scanning-electron microscopy and atomic force microscopy. For the SE analysis, carefully determined sample characteristics were utilized to build a multilayer stack optical model, in order to derive the dielectric functions and refractive indices. The SE-derived absorption coefficients from CZTS/SLG samples were compared with those derived from complementary spectrophotometry measurements and found to be in good agreement. The bandgap determined from Tauc plots was E-g=1.57 +/- 0.02 eV. The absorption coefficients just above the bandgap were found to be a few 10(4) cm(-1) and to exceed 10(5) cm(-1) at energies above similar to 2.5 eV, which is much higher than previously found. The sub-bandgap k-value was found to be k similar to 0.05 or less, suggesting that a moderate band tail is present. Separate device characterization performed on identical samples allowed us to assign device efficiencies of, respectively, 2.8% and 5.3% to the 500 nm and 800 nm-thick samples featured in this study.

  • 4.
    Ren, Yi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Ross, Nils
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsen, Jes K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer-Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Evolution of Cu2ZnSnS4 during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure2017Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 8, s. 3713-3722Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chalcogen-based materials like Cu2ZnSnS4 (CZTS) have attracted extensive attention for applications such as photovoltaics and water splitting. However, an inability to monitor the sulfur partial pressure (P-S2) during the non equilibrium annealing process at high temperatures complicates the synthesis of CZTS with controlled optoelectronic properties. Here we demonstrate that P-S2 can be monitored by investigating the Sn-S phase transformation. We showed that P-S2 drops considerably over the annealing time, causing gradual alterations in CZTS: (i) a change in defect type and (ii) evolution of ZnS and SnxSy phases. With additional ordering treatment, we observed that the low room-temperature photoluminescence energy usually seen in CZTS can result from insufficient P-S2 during annealing. It is proven that remarkable V-oc beyond 700 mV for solar cells with nonoptimal CdS buffer can be repeatedly achieved when CZTS is prepared under a sufficiently high P-S2. An ordering treatment before CdS deposition can further improve V-oc to 783 mV.

  • 5.
    Ross, Nils
    et al.
    Univ Oslo, Ctr Mat Sci & Nanotechnol, Dept Phys, N-0316 Oslo, Norway;Uppsala Univ, Dept Engn Sci, Angstrom Lab, Div Solid State Elect, SE-75121 Uppsala, Sweden.
    Grini, Sigbjorn
    Univ Oslo, Ctr Mat Sci & Nanotechnol, Dept Phys, N-0316 Oslo, Norway.
    Rudisch, Katharina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Vines, Lasse
    Univ Oslo, Ctr Mat Sci & Nanotechnol, Dept Phys, N-0316 Oslo, Norway.
    Platzer Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Selenium Inclusion in Cu2ZnSn(S,Se)(4) Solar Cell Absorber Precursors for Optimized Grain Growth2018Ingår i: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 8, nr 4, s. 1132-1141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu2ZnSn(S,Se)(4) precursors are fabricated by compound cosputtering from metal sulfide and selenide targets, and annealed in mixed argon, sulfur, and selenium atmosphere at temperatures between 540 and 580 degrees C and at pressures between 24 and 47 kPa. We produce solar cell devices from these absorbers that range from 2.0% to 9.0% power conversion efficiency. We extensively characterize the morphology and elemental composition of the absorbers, and are able to closely relate the annealing conditions, precursor sulfur-selenium content, device performance, and absorber quality. We develop a qualitative model which relates the sulfur-selenium distribution in the precursor and the relative partial pressures of sulfur and selenium during the annealing process to the absorber properties. We show that selenium inclusion in the precursor allows more rapid recrystallization of the absorber at lower temperature. Alternating stacking of sulfur and selenium containing precursor material leads to differential rates of recrystallization, which allows some control over the morphology of the annealed absorber and Zn(S,Se) secondary phase segregation in that absorber. We further show that selenium containing precursors can be used to fabricate the superior devices relative to sulfur-only precursors, when the annealing phase space is subject to severe practical restrictions.

  • 6.
    Rudisch, Katharina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Davydova, Alexandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    The effect of stoichiometry on Cu-Zn ordering kinetics in Cu2ZnSnS4 thin film2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 16, artikel-id 161558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu-Zn disorder in Cu2ZnSnS4 (CZTS) may be responsible for the large open circuit voltage deficit in CZTS based solar cells. In this study, it was investigated how composition-dependent defect complexes influence the order-disorder transition. A combinatorial CZTS thin film sample was produced with a cation composition gradient across the sample area. The graded sample was exposed to various temperature treatments and the degree of order was analyzed with resonant Raman spectroscopy for various compositions ranging from E- and A-type to B-, F-, and C-type CZTS. We observe that the composition has no influence on the critical temperature of the order-disorder transition, but strongly affects the activation energy. Reduced activation energy is achieved with compositions with Cu/Sn > 2 or Cu/Sn < 1.8 suggesting an acceleration of the cation ordering in the presence of vacancies or interstitials. This is rationalized with reference to the effect of point defects on exchange mechanisms. The implications for reducing disorder in CZTS thin films are discussed in light of the new findings.

  • 7.
    Rudisch, Katharina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Espinosa-Garcia, William F.
    Univ San Buenaventura Medellin, Fac Ingn, Grp Invest Modelamiento & Simulac Computac, Carrera 56C 51-110, Medellin, Colombia.
    Osorio-Guillen, Jorge M.
    Univ Antioquia UdeA, Inst Fis, Calle 70 52-21,Carrera 56C 51-110, Medellin, Colombia.
    Araujo, Carlos Moyses
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Platzer Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Structural and Electronic Properties of Cu2MnSnS4 from Experiment and First-Principles Calculations2019Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 256, nr 7, artikel-id 1800743Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu2MnSnS4 shares several promising properties with the widely investigated Cu2ZnSnS4 for photovoltaic applications such as containing only earth abundant and non-toxic elements, and suitable absorption characteristics for absorber materials. Thin film Cu2MnSnS4 samples with various cation compositions are co-sputtered reactively followed by a high temperature anneal. Formation of Cu2MnSnS4 and co-existence of several secondary phases is verified by XRD and Raman. Our investigation of the crystal structure based on first-principles DFT confirms that stannite crystal structure is preferred over kesterite, although, further verification considering cation disorder is needed. The direct band gap of Cu2MnSnS4 is calculated as 1.52 eV (1.62 eV) for stannite (kesterite), which coincides with the range of the measured band gaps from spectrophotometry of 1.42-1.59 eV. After further annealing treatments below 240 degrees C, the absorption shows reversible changes: the band gap blue-shifts and the Urbach tail energy is reduced. It is concluded that, just like Cu2ZnSnS4, disorder also occurs in Cu2MnSnS4. The implications of our findings are discussed and related to the current understanding of cation disorder in Cu2ZnSnS4 and related compounds. Furthermore, for the first time first-principles DFT investigations are presented for the thiospinel Cu2MnSn3S8 which is observed experimentally as a secondary phase in Sn-rich Cu2MnSnS4 thin films.

  • 8.
    Rudisch, Katharina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Ren, Yi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer-Björkman, Charlotte
    Scragg, Jonathan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Order-disorder transition in B-type Cu2ZnSnS4 and limitations of ordering through thermal treatments2016Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, nr 23, artikel-id 231902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    B-type Cu2ZnSnS4 (CZTS) thin films with varying degrees of cation order were produced and examined with resonant Raman spectroscopy. Simulations based on Vineyard's theory of order allowed kinetic analysis of the final degree of order after the applied thermal treatments. Combining the results from the simulations and the resonant Raman spectra, the kinetic parameters within the Vineyard model for the order-disorder transition in B-type CZTS were determined, as well as a method which allows quantification of the degree of order based on resonant Raman spectra. The knowledge gained about the order-disorder transition in B-type CZTS allowed the prediction of a best practice thermal treatment for high ordering. This further leads to awareness about practical limits of thermal treatments regarding the cation ordering in B-type CZTS, and suggests that such treatments are not able to produce the high cation order necessary to sufficiently reduce detrimental potential fluctuations. Published by AIP Publishing.

1 - 8 av 8
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