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See detailSynthesis, theoretical and experimental characterisation of thin film Cu2Sn1-xGexS3 ternary alloys (x = 0 to 1): Homogeneous intermixing of Sn and Ge
Robert, Erika UL; Gunder, René; De Wild, Jessica UL et al

in Acta Materialia (2018), 151

Cu2Sn1-xGexS3 is a p-type semiconductor alloy currently investigated for use as an absorber layer in thin film solar cells. The aim of this study is to investigate the properties of this alloy in thin ... [more ▼]

Cu2Sn1-xGexS3 is a p-type semiconductor alloy currently investigated for use as an absorber layer in thin film solar cells. The aim of this study is to investigate the properties of this alloy in thin film form in order to establish relationships between group IV composition and structural, vibrational and opto-electronic properties. Seven single phase Cu2Sn1-xGexS3 films are prepared from x ¼ 0 to 1, showing a uniform distribution of Ge and Sn laterally and in depth. The films all show a monoclinic crystal structure. The lattice parameters are extracted using Le Bail refinement and show a linear decrease with increasing Ge content. Using density-functional theory with hybrid functionals, we calculate the Raman active phonon frequencies of Cu2SnS3 and Cu2GeS3. For the alloyed compounds, we use a virtual atom approximation. The shift of the main Raman peak from x ¼ 0 to x ¼ 1 can be explained as being half due to the change in atomic masses and half being due to the different bond strength. The bandgaps of the alloys are extracted from photoluminescence measurements and increase linearly from about 0.90 to 1.56 eV with increasing Ge. The net acceptor density of all films is around 1018 cm 3. These analyses have established that the alloy forms a solid solution over the entire composition range meaning that intentional band gap grading should be possible for future absorber layers. The linear variation of the unit cell parameters and the band gap with group IV content allows composition determination by scattering or optical measurements. Further research is required to reduce the doping density by two orders of magnitude in order to improve the current collection within a solar cell device structure. [less ▲]

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See detailINVESTIGATION OF THE CU2(SN,GE)S3 TERNARY ALLOY FOR THIN FILM SOLAR CELLS
Robert, Erika UL

Doctoral thesis (2018)

This thesis examines material properties of the novel Cu2(Sn, Ge)S3 alloy, from the perspective of a solar cell scientist searching for a new light absorbing material to produce highly efficient thin-film ... [more ▼]

This thesis examines material properties of the novel Cu2(Sn, Ge)S3 alloy, from the perspective of a solar cell scientist searching for a new light absorbing material to produce highly efficient thin-film devices. [less ▲]

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See detailPotassium fluoride ex-situ treatment on both Cu-rich and Cu-poor CuInSe2 thin film solar cells
Elanzeery, Hossam UL; Babbe, Finn UL; Melchiorre, Michele UL et al

in IEEE Journal of Photovoltaics (2017), 7(2), 684-689

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See detailElectrodeposition of germanium-containing precursors for Cu2(Sn,Ge)S3 thin film solar cells
Malaquias, Joao Corujo Branco UL; Wu, Minxian; Lin, Jiajia et al

in Electrochimica Acta (2017)

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See detailSilver Doped Cu2SnS3 Absorber Layers for Solar Cells Application
De Wild, Jessica UL; Babbe, Finn UL; Robert, Erika UL et al

in IEEE Journal of Photovoltaics (2017)

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See detailCrystallographic and optoelectronic properties of the novel thin film absorber Cu2GeS3
Robert, Erika UL; De Wild, Jessica UL; Colombara, Diego UL et al

in Proceedings of SPIE (2016, September)

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See detailChemical stability of the Cu2SnS3/Mo interface
De Wild, Jessica UL; Robert, Erika UL; Dale, Phillip UL

Poster (2016, June)

Cu2SnS3 is an earth abundant semiconductor researched for photovoltaic applications. Due to the small energy difference in the Sn2+/4+ oxidation states and low free energy of MoS2, the Cu2SnS3/Mo ... [more ▼]

Cu2SnS3 is an earth abundant semiconductor researched for photovoltaic applications. Due to the small energy difference in the Sn2+/4+ oxidation states and low free energy of MoS2, the Cu2SnS3/Mo interface is unstable and Cu2SnS3 decomposes. The interface is stabilized by growing Cu2SnS3 on a thin MoS2 layer. Photoluminescence occurs only at the back of the Cu2SnS3 layers when grown on MoS2 and no quantifiable amounts of Cu and Sn are measured at the MoS2 substrate. The quenching of emission of Cu2SnS3 grown on Mo is due to binary sulfides formed in presence of Mo which are not formed when Cu2SnS3 is grown on MoS2. [less ▲]

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See detailSecondary phase formation during monoclinic Cu2SnS3 growth for solar cell application
De Wild, Jessica UL; Robert, Erika UL; El Adib, Brahime et al

in Solar Energy Materials and Solar Cells (2016)

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See detail13.3% efficient solution deposited Cu(In,Ga)Se 2 solar cells processed with different sodium salt sources
Berner, Ulrich; Colombara, Diego UL; De Wild, Jessica UL et al

in Progress in Photovoltaics Research and Applications (2015)

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See detailCu2SnS3-based thin film solar cell from electrodeposition-annealing route
Robert, Erika UL; De Wild, Jessica UL; Dale, Phillip UL

in IEEE Proceedings (2015, June)

Cu2SnS3 is a new emerging material for thin film photovoltaics, composed of three abundant and non toxic elements. Its p-type conductivity, bandgap of 0.93 eV and absorption coefficient above 104 cm-1 ... [more ▼]

Cu2SnS3 is a new emerging material for thin film photovoltaics, composed of three abundant and non toxic elements. Its p-type conductivity, bandgap of 0.93 eV and absorption coefficient above 104 cm-1 make it a promising absorber layer for p-n heterojunction devices. In this study, the Cu2SnS3 absorber is synthesized from electroplated stacked Cu-Sn precursors further annealed in chalcogen atmosphere (S and SnS). The electroplating has been processed on upscaled 45 x 50 mm2 Mo-coated soda-lime glass substrates on which the metallic layers seem to delaminate easily from the substrate due to increased stress between them. To reduce this stress the precursors are subjected to pre-alloying treatments. The effects of pre-alloying are investigated in terms of final absorber morphology, composition and crystal structure. Precursors are annealed at 250°C and 350°C. The prealloying at 350°C is far above the melting point of Sn around 230°C and these samples show de-wetting. The as-deposited and 250°C pre-alloyed samples are processed further into absorber layers and solar cells. The finished absorber layers show mainly monoclinic Cu2SnS3. Absorbers completed into devices show a device power conversion efficiency of 0.64%. The spectral response suggests the existence of two bandgaps, consistent with previous results. [less ▲]

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See detailQuantification of surface ZnSe in Cu2ZnSnSe4-based solar cells by analysis of the spectral response
Colombara, Diego UL; Robert, Erika UL; Crossay, Alexandre UL et al

in Solar Energy Materials & Solar Cells (2014), 123

Absorber layers consisting of Cu2ZnSnSe4 (CZTSe) and surface ZnSe in variable ratios were prepared by selenization of electroplated Cu/Sn/Zn precursors and completed into full devices with up to 5.6 ... [more ▼]

Absorber layers consisting of Cu2ZnSnSe4 (CZTSe) and surface ZnSe in variable ratios were prepared by selenization of electroplated Cu/Sn/Zn precursors and completed into full devices with up to 5.6 % power conversion efficiency. The loss of short circuit current density for samples with increasing ZnSe content is consistent with an overall reduction of spectral response, pointing to a ZnSe current blocking behavior. A feature in the spectral response centered around 3 eV was identified and attributed to light absorption by ZnSe. A model is proposed to account for additional collection of the carriers generated underneath ZnSe capable of diffusing across to the space charge region. The model satisfactorily reproduces the shape of the spectral response and the estimated ZnSe surface coverage is in good qualitative agreement with analysis of the Raman spectral mapping. The model emphasizes the importance of the ZnSe morphology on the spectral response, and its consequences on the solar cell device performance. [less ▲]

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See detailFabrication and characterization of kesterite Cu2ZnSnS4 thin films deposited by electrostatic spray assisted vapour deposition method
Liu, J. P.; Choy, Kwang-Leong; Placidi, M. et al

in Physica Status Solidi A. Applications and Materials Science (2014)

Most of the high efficiency kesterite solar cells are fabricated by vacuum or hydrazine-based solution methods which have drawbacks, such as high cost, high toxicity or explosivity. In our contribution ... [more ▼]

Most of the high efficiency kesterite solar cells are fabricated by vacuum or hydrazine-based solution methods which have drawbacks, such as high cost, high toxicity or explosivity. In our contribution, an alternative non-vacuum and environmental friendly deposition technology called electrostatic spray assisted vapour deposition (ESAVD) has been used for the cost-effective growth of Cu2ZnSnS4 (CZTS) thin films with well controlled structure and composition. CZTS films have been characterized using a combination of XRD, XPS, SEM-EDX, AFM, and Raman spectroscopy. The results demonstrated that adherent, uniform and homogeneous CZTS films without apparent secondary phases have been produced by ESAVD. The atomic ratios measured by EDX are Cu/(Zn + Sn) = 0.88 and Zn/Sn = 1.17,which are very close with the reported high efficiency solar cells and can be finely tuned by formulating the precursor.CZTS films exhibited a typical optical band gap of 1.53 eV from UV–Vis analysis. Cu2ZnSnS4 produced by the ESAVD are being optimized towards the fabrication of high efficiency photovoltaic devices. [less ▲]

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See detailOptoelectronic Analysis of Kesterite Based Solar Cells
Robert, Erika UL

Bachelor/master dissertation (2013)

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