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Ishiang Shih - One of the best experts on this subject based on the ideXlab platform.

  • Junction by Diffusion of Elemental Sodium Alone into Bridgman Cu(In, Ga) Se2
    2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017
    Co-Authors: S. Park, C. H. Champness, S. Vanka, Ishiang Shih
    Abstract:

    The diffusion of Elemental Sodium into p-type Bridgman-grown CuInSe 2+x has already been shown to create a pn-junction by its presence alone [1], provided the molecular amount of added [Na] exceeds the quantity $2\mathrm{x}+\delta$ [2], (from the excess Se). Here, $\delta$ is the excess of Se found experimentally in the p-type but stoichiometrically-grown material (i.e.with $\mathrm{x}=0$ ). The present contribution demonstrates similar action in Bridgman-grown p-type quaternary Cu(In 1-y ,Ga y )Se 2 , with $\mathrm{y}=0.2$ and 0.3. The existence of deep (more than 6 microns) junctions after the Na-diffusion, is demonstrated by sample lapping and hot probing with, photovoltaic and EBIC action. Information from XPS and XRD is also presented.

  • Effect of Sodium diffused into Bridgman CuInSe2+x
    Journal of Electron Spectroscopy and Related Phenomena, 2016
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    Abstract The study describes diffusion of Elemental Sodium into p -type samples of Bridgman-grown CuInSe 2+x , causing a change from p - to n -type behavior at the surface and deep into the material. This resulted in the creation of Na 1s and Se 3d XPS peaks at binding energies of 1071 and 54.5 eV respectively, where the latter has been attributed to CuInSe 2 itself. Subsequent annealing of the samples in air gave rise to a second Se 3d peak at 59 eV, attributed to Na 2 SeO 3 by oxidation of Na 2 Se. However, SeO 2 also gives a peak at about the same binding energy. The presence of the diffused-in Na up to about 10% at the surface appears to promote the creation of a high ratio [Se]/[Cu] compound at the expense of the chalcopyrite at the sample surface. The diffused-in samples showed n/p homojunctions at depths of tens of microns for stoichiometric CuInSe 2 and at smaller depths for CuInSe 2.2 , with excess Se content. Estimates of the diffusion coefficient for Na into the Bridgman samples at 250 °C were in the range of 10 −10 –10 −8  cm 2 /s.

  • XPS Se 3d peaks in Na-added Bridgman CuInSe2+x
    2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    XPS measurements were made on samples from multi-crystalized ingots grown from Bridgman melts, having a composition corresponding to the formula CuInSe2+x, containing added quantities of Elemental Sodium or Na2Se. Special attention was paid to the XPS peaks Se 3d, Na 1s and O 1s. In particular, two main Se 3d peaks were observed at binding energies of 54.5 and 59 eV. The first of these, previously assigned to ternary CuInSe2, increased with etching depth from the ingot surface but was little affected by the presence of Na. However, the second peak only appeared when Na or Na2Se had been added to the melt. The 59 eV peak also increased somewhat with contaminant oxygen content and was assigned tentatively to Na2SeO3.

  • Characteristics of XPS Se 3d peaks in crystalline Bridgman CuInSe2+x with added Sodium in the melt
    Journal of Electron Spectroscopy and Related Phenomena, 2015
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    Abstract Using multi-crystalline samples of Bridgman-grown CuInSe2+x, containing added quantities of Elemental Sodium or Na2Se, detailed XPS measurements were made to determine the location and action of the Sodium. Here, the XPS peaks Se 3d, Na 1s and O 1s were given special attention. In particular, two main 3d peaks were observed at binding energies of 54.5 and 59 eV. The first of these, previously assigned mainly to the basic CuInSe2 compound, increased with argon etching time, starting from the ingot surface, but was little affected by the presence of the Na. However, the second peak only appeared when Na or Na2Se had been previously added to the melt. The intensity of this 59 eV peak increased with that of the Na 1s peak at 1071 eV at the surface and with the atomic percentage of the Na added to the Bridgman melt. It also increased somewhat with the amount of contaminant oxygen present in the ingots. The 59 eV peak was thus tentatively assigned to Na2SeO3 resulting from the air-oxidation of Na2Se.

  • electrical effect of introducing Elemental Sodium into the bridgman melt of cuinse2 x crystals
    Journal of Crystal Growth, 2014
    Co-Authors: Hadley Myers, C. H. Champness, Ishiang Shih
    Abstract:

    Abstract Transport and other measurements have been made on CuInSe2+x samples obtained from Bridgman ingots grown from melts containing controlled amounts of Elemental Sodium, where x represents the excess of Se over stoichiometry. Thermoelectric power and Hall coefficient at room temperature show a conductivity sign change from p- to n-type in otherwise stoichiometric CuInSe2 (x=0), with added Na between 0.2 and 0.3 at%. It is further found that the critical amount of Na required to change the conductivity type, denoted by [Na]crit, increases with x, almost linearly, with an initial slope of 2, corresponding to an approximate formula of [Na]crit=2x+δ, where δ is found to be 0.25 at% Na. This behavior can be accounted for quantitatively using a ‘selenium starvation’ model, whereby at the p-to-n type change, two atoms of Sodium have reacted with one atom of Se to form a molecule like Na2Se, with an atom-to-atom ratio [Na]/[Se]=2. Such molecules were detected in growth run residues. However, no Na or Na compounds were detected in the interior of bulk crystals. In stoichiometric material (x=0), the crystal structure remained chalcopyrite with up to at least 3 at% Na in the melt, despite the conductivity type changes. Further, no β-phase was detected in the bulk material by XRD but it was found at the surface of samples by XPS.

Tsampas M. N. - One of the best experts on this subject based on the ideXlab platform.

  • An Electrochemical Study on the Cathode of the Intermediate Temperature Tubular Sodium-Sulfur (NaS) Battery
    Journal of the Electrochemical Society 166 A135-A142, 2019
    Co-Authors: Nikiforidis G., Jongerden G. J., Jongerden E. F., M. C. M. Van De Sanden, Tsampas M. N.
    Abstract:

    The development of low-cost energy storage schemes is imminent in light of the ever-growing demand of electricity. Sodium-sulfur (NaS) batteries offer low-cost technology for energy storage applications due to the intrinsically high capacities of Elemental Sodium and sulfur as well as their abundant resources. Operating this battery technology on the intermediate range (130-200 degrees C) can lead to lower material costs, mitigate thermal management and safety issues and enhance cycle life. Herein, an electrochemical study on the cathode of the IT NaS cell is performed at 150 degrees C and a concentration range of 1.5 to 3 M Sodium pentasulfide dissolved in tetraglyme, showing a robust long term performance (42 days of continuous cycling) with a volumetric energy density of 83 Wh L-1. Most importantly, the cell was eligible for a tenfold volume scale-up considerably enhancing its capacity (790 mAh) but in the same time somewhat hindered by mass transport, especially during the end of the discharge process as manifested by electrochemical impedance spectroscopy.

Tsampas M - One of the best experts on this subject based on the ideXlab platform.

  • An electrochemical study on the cathode of the intermediate temperature tubular Sodium-sulfur (NAS) battery
    Electrochemical Society Inc., 2019
    Co-Authors: Nikiforidis Georgios, Gj Jongerden, Ef Jongerden, Sanden, Mcm Richard Van De, Tsampas M
    Abstract:

    \u3cp\u3eThe development of low-cost energy storage schemes is imminent in light of the ever-growing demand of electricity. Sodium-sulfur (NaS) batteries offer low-cost technology for energy storage applications due to the intrinsically high capacities of Elemental Sodium and sulfur as well as their abundant resources. Operating this battery technology on the intermediate range (130-200\u3csup\u3e◦\u3c/sup\u3eC) can lead to lower material costs, mitigate thermal management and safety issues and enhance cycle life. Herein, an electrochemical study on the cathode of the IT NaS cell is performed at 150\u3csup\u3e◦\u3c/sup\u3eC and a concentration range of 1.5 to 3 M Sodium pentasulfide dissolved in tetraglyme, showing a robust long term performance (42 days of continuous cycling) with a volumetric energy density of 83 Wh L−\u3csup\u3e1\u3c/sup\u3e. Most importantly, the cell was eligible for a tenfold volume scale-up considerably enhancing its capacity (790 mAh) but in the same time somewhat hindered by mass transport, especially during the end of the discharge process as manifested by electrochemical impedance spectroscopy.\u3c/p\u3

Nikiforidis G. - One of the best experts on this subject based on the ideXlab platform.

  • An Electrochemical Study on the Cathode of the Intermediate Temperature Tubular Sodium-Sulfur (NaS) Battery
    Journal of the Electrochemical Society 166 A135-A142, 2019
    Co-Authors: Nikiforidis G., Jongerden G. J., Jongerden E. F., M. C. M. Van De Sanden, Tsampas M. N.
    Abstract:

    The development of low-cost energy storage schemes is imminent in light of the ever-growing demand of electricity. Sodium-sulfur (NaS) batteries offer low-cost technology for energy storage applications due to the intrinsically high capacities of Elemental Sodium and sulfur as well as their abundant resources. Operating this battery technology on the intermediate range (130-200 degrees C) can lead to lower material costs, mitigate thermal management and safety issues and enhance cycle life. Herein, an electrochemical study on the cathode of the IT NaS cell is performed at 150 degrees C and a concentration range of 1.5 to 3 M Sodium pentasulfide dissolved in tetraglyme, showing a robust long term performance (42 days of continuous cycling) with a volumetric energy density of 83 Wh L-1. Most importantly, the cell was eligible for a tenfold volume scale-up considerably enhancing its capacity (790 mAh) but in the same time somewhat hindered by mass transport, especially during the end of the discharge process as manifested by electrochemical impedance spectroscopy.

Clifford H. Champness - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Sodium diffused into Bridgman CuInSe2+x
    Journal of Electron Spectroscopy and Related Phenomena, 2016
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    Abstract The study describes diffusion of Elemental Sodium into p -type samples of Bridgman-grown CuInSe 2+x , causing a change from p - to n -type behavior at the surface and deep into the material. This resulted in the creation of Na 1s and Se 3d XPS peaks at binding energies of 1071 and 54.5 eV respectively, where the latter has been attributed to CuInSe 2 itself. Subsequent annealing of the samples in air gave rise to a second Se 3d peak at 59 eV, attributed to Na 2 SeO 3 by oxidation of Na 2 Se. However, SeO 2 also gives a peak at about the same binding energy. The presence of the diffused-in Na up to about 10% at the surface appears to promote the creation of a high ratio [Se]/[Cu] compound at the expense of the chalcopyrite at the sample surface. The diffused-in samples showed n/p homojunctions at depths of tens of microns for stoichiometric CuInSe 2 and at smaller depths for CuInSe 2.2 , with excess Se content. Estimates of the diffusion coefficient for Na into the Bridgman samples at 250 °C were in the range of 10 −10 –10 −8  cm 2 /s.

  • XPS Se 3d peaks in Na-added Bridgman CuInSe2+x
    2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    XPS measurements were made on samples from multi-crystalized ingots grown from Bridgman melts, having a composition corresponding to the formula CuInSe2+x, containing added quantities of Elemental Sodium or Na2Se. Special attention was paid to the XPS peaks Se 3d, Na 1s and O 1s. In particular, two main Se 3d peaks were observed at binding energies of 54.5 and 59 eV. The first of these, previously assigned to ternary CuInSe2, increased with etching depth from the ingot surface but was little affected by the presence of Na. However, the second peak only appeared when Na or Na2Se had been added to the melt. The 59 eV peak also increased somewhat with contaminant oxygen content and was assigned tentatively to Na2SeO3.

  • Characteristics of XPS Se 3d peaks in crystalline Bridgman CuInSe2+x with added Sodium in the melt
    Journal of Electron Spectroscopy and Related Phenomena, 2015
    Co-Authors: Sunyoung Park, Clifford H. Champness, Ishiang Shih
    Abstract:

    Abstract Using multi-crystalline samples of Bridgman-grown CuInSe2+x, containing added quantities of Elemental Sodium or Na2Se, detailed XPS measurements were made to determine the location and action of the Sodium. Here, the XPS peaks Se 3d, Na 1s and O 1s were given special attention. In particular, two main 3d peaks were observed at binding energies of 54.5 and 59 eV. The first of these, previously assigned mainly to the basic CuInSe2 compound, increased with argon etching time, starting from the ingot surface, but was little affected by the presence of the Na. However, the second peak only appeared when Na or Na2Se had been previously added to the melt. The intensity of this 59 eV peak increased with that of the Na 1s peak at 1071 eV at the surface and with the atomic percentage of the Na added to the Bridgman melt. It also increased somewhat with the amount of contaminant oxygen present in the ingots. The 59 eV peak was thus tentatively assigned to Na2SeO3 resulting from the air-oxidation of Na2Se.

  • Electrical effect of introducing Elemental Sodium into the Bridgman melt of CuInSe2+x crystals
    Journal of Crystal Growth, 2014
    Co-Authors: Hadley F. Myers, Clifford H. Champness, Ishiang Shih
    Abstract:

    Abstract Transport and other measurements have been made on CuInSe2+x samples obtained from Bridgman ingots grown from melts containing controlled amounts of Elemental Sodium, where x represents the excess of Se over stoichiometry. Thermoelectric power and Hall coefficient at room temperature show a conductivity sign change from p- to n-type in otherwise stoichiometric CuInSe2 (x=0), with added Na between 0.2 and 0.3 at%. It is further found that the critical amount of Na required to change the conductivity type, denoted by [Na]crit, increases with x, almost linearly, with an initial slope of 2, corresponding to an approximate formula of [Na]crit=2x+δ, where δ is found to be 0.25 at% Na. This behavior can be accounted for quantitatively using a ‘selenium starvation’ model, whereby at the p-to-n type change, two atoms of Sodium have reacted with one atom of Se to form a molecule like Na2Se, with an atom-to-atom ratio [Na]/[Se]=2. Such molecules were detected in growth run residues. However, no Na or Na compounds were detected in the interior of bulk crystals. In stoichiometric material (x=0), the crystal structure remained chalcopyrite with up to at least 3 at% Na in the melt, despite the conductivity type changes. Further, no β-phase was detected in the bulk material by XRD but it was found at the surface of samples by XPS.

  • Optical absorption measurements in the wavelength range 1.3-1.6 microns in Bridgman CuInSe 2 grown from melts with added Sodium
    2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013
    Co-Authors: An Qi Jin, Hadley F. Myers, Clifford H. Champness, I. Shih
    Abstract:

    Measurements of optical absorption coefficient (α) were made on Bridgman-grown CuInSe2 samples, over the wavelength range 1300 to 1600 nm, at room temperature. The samples were obtained from multi-crystalline ingots, grown from melts of composition CuInSe2+x, plus y atomic % of Elemental Sodium. Here, x, the excess of Se over stoichiometry, ranged from 0 to 0.4 and y, the percentage of Na in the melt, ranged from 0 to 11 at %. It was found that α was considerably increased by the original Na in the melt and also by a stoichiometric deficiency of Se in the melt; that is with a melt formula corresponding to CuInSe1.8, (or x = - 0.2). A smaller increase of α was observed with increase of x, the Se excess. With the addition of Na2Se in the melt, little change was obtained compared with the large increase with Elemental Na.