TY  - JOUR
AU  - Radmilović, Vuk
AU  - Goebelt, Manuela
AU  - Ophus, Colin
AU  - Christiansen, Silke
AU  - Spiecker, Erdmann
AU  - Radmilović, Velimir R.
PY  - 2017
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3633
AB  - This article focuses on the microscopic mechanism of thermally induced nanoweld formation between silver nanowires (AgNWs) which is a key process for improving electrical conductivity in NW networks employed for transparent electrodes. Focused ion beam sectioning and transmission electron microscopy were applied in order to elucidate the atomic structure of a welded NW including measurement of the wetting contact angle and characterization of defect structure with atomic accuracy, which provides fundamental information on the welding mechanism. Crystal lattice strain, obtained by direct evaluation of atomic column displacements in high resolution scanning transmission electron microscopy images, was shown to be non-uniform among the five twin segments of the AgNW pentagonal structure. It was found that the pentagonal cross-sectional morphology of AgNWs has a dominant effect on the formation of nanowelds by controlling initial wetting as well as diffusion of Ag atoms between the NWs. Due to complete solid-state wetting, at an angle of similar to 4.8 degrees, the welding process starts with homoepitaxial nucleation of an initial Ag layer on (100) surface facets, considered to have an infinitely large radius of curvature. However, the strong driving force for this process due to the Gibbs-Thomson effect, requires the NW contact to occur through the corner of the pentagonal cross-section of the second NW providing a small radius of curvature. After the initial layer is formed, the welded zone continues to grow and extends out epitaxially to the neighboring twin segments.
PB  - IOP Publishing Ltd, Bristol
T2  - Nanotechnology
T1  - Low temperature solid-state wetting and formation of nanowelds in silver nanowires
IS  - 38
VL  - 28
DO  - 10.1088/1361-6528/aa7eb8
ER  - 

@article{
author = "Radmilović, Vuk and Goebelt, Manuela and Ophus, Colin and Christiansen, Silke and Spiecker, Erdmann and Radmilović, Velimir R.",
year = "2017",
abstract = "This article focuses on the microscopic mechanism of thermally induced nanoweld formation between silver nanowires (AgNWs) which is a key process for improving electrical conductivity in NW networks employed for transparent electrodes. Focused ion beam sectioning and transmission electron microscopy were applied in order to elucidate the atomic structure of a welded NW including measurement of the wetting contact angle and characterization of defect structure with atomic accuracy, which provides fundamental information on the welding mechanism. Crystal lattice strain, obtained by direct evaluation of atomic column displacements in high resolution scanning transmission electron microscopy images, was shown to be non-uniform among the five twin segments of the AgNW pentagonal structure. It was found that the pentagonal cross-sectional morphology of AgNWs has a dominant effect on the formation of nanowelds by controlling initial wetting as well as diffusion of Ag atoms between the NWs. Due to complete solid-state wetting, at an angle of similar to 4.8 degrees, the welding process starts with homoepitaxial nucleation of an initial Ag layer on (100) surface facets, considered to have an infinitely large radius of curvature. However, the strong driving force for this process due to the Gibbs-Thomson effect, requires the NW contact to occur through the corner of the pentagonal cross-section of the second NW providing a small radius of curvature. After the initial layer is formed, the welded zone continues to grow and extends out epitaxially to the neighboring twin segments.",
publisher = "IOP Publishing Ltd, Bristol",
journal = "Nanotechnology",
title = "Low temperature solid-state wetting and formation of nanowelds in silver nanowires",
number = "38",
volume = "28",
doi = "10.1088/1361-6528/aa7eb8"
}

Radmilović, V., Goebelt, M., Ophus, C., Christiansen, S., Spiecker, E.,& Radmilović, V. R.. (2017). Low temperature solid-state wetting and formation of nanowelds in silver nanowires. in Nanotechnology
IOP Publishing Ltd, Bristol., 28(38).
https://doi.org/10.1088/1361-6528/aa7eb8

Radmilović V, Goebelt M, Ophus C, Christiansen S, Spiecker E, Radmilović VR. Low temperature solid-state wetting and formation of nanowelds in silver nanowires. in Nanotechnology. 2017;28(38).
doi:10.1088/1361-6528/aa7eb8 .

Radmilović, Vuk, Goebelt, Manuela, Ophus, Colin, Christiansen, Silke, Spiecker, Erdmann, Radmilović, Velimir R., "Low temperature solid-state wetting and formation of nanowelds in silver nanowires" in Nanotechnology, 28, no. 38 (2017),
https://doi.org/10.1088/1361-6528/aa7eb8 . .

TY  - JOUR
AU  - Guo, Fei
AU  - Li, Ning
AU  - Radmilović, Vuk
AU  - Radmilović, Velimir R.
AU  - Turbiez, Mathieu
AU  - Spiecker, Erdmann
AU  - Forberich, Karen
AU  - Brabec, Christoph J.
PY  - 2015
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2966
AB  - We report in this work efficient, fully printed tandem organic solar cells (OSCs) using solution-processed silver as the reflective bottom electrode and silver nanowires as the transparent top electrode. Employing two different band-gap photoactive materials with complementary absorption, the tandem OSCs are fully printed under ambient conditions without the use of indium tin oxide and vacuum-based deposition. The fully printed tandem devices achieve power conversion efficiencies of 5.81% (on glass) and 4.85% (on flexible substrate) without open circuit voltage (V-oc) losses. These results represent an important progress towards the realization of low-cost tandem OSCs by demonstrating the possibility of printing efficient organic tandem devices under ambient conditions onto production relevant carrier substrates.
PB  - Royal Soc Chemistry, Cambridge
T2  - Energy & Environmental Science
T1  - Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes
EP  - 1697
IS  - 6
SP  - 1690
VL  - 8
DO  - 10.1039/c5ee00184f
ER  - 

@article{
author = "Guo, Fei and Li, Ning and Radmilović, Vuk and Radmilović, Velimir R. and Turbiez, Mathieu and Spiecker, Erdmann and Forberich, Karen and Brabec, Christoph J.",
year = "2015",
abstract = "We report in this work efficient, fully printed tandem organic solar cells (OSCs) using solution-processed silver as the reflective bottom electrode and silver nanowires as the transparent top electrode. Employing two different band-gap photoactive materials with complementary absorption, the tandem OSCs are fully printed under ambient conditions without the use of indium tin oxide and vacuum-based deposition. The fully printed tandem devices achieve power conversion efficiencies of 5.81% (on glass) and 4.85% (on flexible substrate) without open circuit voltage (V-oc) losses. These results represent an important progress towards the realization of low-cost tandem OSCs by demonstrating the possibility of printing efficient organic tandem devices under ambient conditions onto production relevant carrier substrates.",
publisher = "Royal Soc Chemistry, Cambridge",
journal = "Energy & Environmental Science",
title = "Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes",
pages = "1697-1690",
number = "6",
volume = "8",
doi = "10.1039/c5ee00184f"
}

Guo, F., Li, N., Radmilović, V., Radmilović, V. R., Turbiez, M., Spiecker, E., Forberich, K.,& Brabec, C. J.. (2015). Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes. in Energy & Environmental Science
Royal Soc Chemistry, Cambridge., 8(6), 1690-1697.
https://doi.org/10.1039/c5ee00184f

Guo F, Li N, Radmilović V, Radmilović VR, Turbiez M, Spiecker E, Forberich K, Brabec CJ. Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes. in Energy & Environmental Science. 2015;8(6):1690-1697.
doi:10.1039/c5ee00184f .

Guo, Fei, Li, Ning, Radmilović, Vuk, Radmilović, Velimir R., Turbiez, Mathieu, Spiecker, Erdmann, Forberich, Karen, Brabec, Christoph J., "Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes" in Energy & Environmental Science, 8, no. 6 (2015):1690-1697,
https://doi.org/10.1039/c5ee00184f . .

TY  - JOUR
AU  - Goebelt, Manuela
AU  - Keding, Ralf
AU  - Schmitt, Sebastian W.
AU  - Hoffmann, Bjoern
AU  - Jaeckle, Sara
AU  - Latzel, Michael
AU  - Radmilović, Vuk
AU  - Radmilović, Velimir R.
AU  - Spiecker, Erdmann
AU  - Christiansen, Silke
PY  - 2015
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3061
AB  - We report on the development of a novel nano-composite transparent electrode material to be used in various energy applications e.g. as contacts for solar cells, composed of a wet-chemically synthesized silver nanowire (AgNW) network encapsulated in a transparent conductive oxide (TCO) which was deposited with nano-scale precision by atomic layer deposition (ALD). The AgNWs form a random network on a substrate of choice when being drop casted. ALD encapsulation of AgNWs guarantees a conformal and thickness controlled coating of the wires e.g. by the selected aluminum doped zinc oxide (AZO). Annealing of the AgNWs prior to ALD coating, yield a local sintering of AgNWs at their points of intersection, which improves the conductivity of the composite electrodes by reducing their sheet resistance. To demonstrate the performance of these AgNW/AZO composite transparent electrodes, they were used as a top electrode on wafer-based silicon (Si) - solar cells. A novel combination of scanning electron microscopy and image processing is used to determine the degree of percolation of the AgNWs on large areas of the nano-composite AgNW/AZO electrodes. Our results show that the solar cell with percolated AgNW/AZO electrode show the highest short circuit current density (28 mA/cm(2)) and a series resistance in the same order of magnitude compared to reference solar cells with a thermally evaporated silver grid electrode. The electrode example we chose reveals that the developed AgNW/AZO electrode is a technologically relevant and cheap alternative to conventional solar cell screen printed grid electrodes, which contain similar to 95% more Ag per device area, with a high potential to be further systematically optimized by the presented image processing method.
PB  - Elsevier, Amsterdam
T2  - Nano Energy
T1  - Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes
EP  - 206
SP  - 196
VL  - 16
DO  - 10.1016/j.nanoen.2015.06.027
ER  - 

@article{
author = "Goebelt, Manuela and Keding, Ralf and Schmitt, Sebastian W. and Hoffmann, Bjoern and Jaeckle, Sara and Latzel, Michael and Radmilović, Vuk and Radmilović, Velimir R. and Spiecker, Erdmann and Christiansen, Silke",
year = "2015",
abstract = "We report on the development of a novel nano-composite transparent electrode material to be used in various energy applications e.g. as contacts for solar cells, composed of a wet-chemically synthesized silver nanowire (AgNW) network encapsulated in a transparent conductive oxide (TCO) which was deposited with nano-scale precision by atomic layer deposition (ALD). The AgNWs form a random network on a substrate of choice when being drop casted. ALD encapsulation of AgNWs guarantees a conformal and thickness controlled coating of the wires e.g. by the selected aluminum doped zinc oxide (AZO). Annealing of the AgNWs prior to ALD coating, yield a local sintering of AgNWs at their points of intersection, which improves the conductivity of the composite electrodes by reducing their sheet resistance. To demonstrate the performance of these AgNW/AZO composite transparent electrodes, they were used as a top electrode on wafer-based silicon (Si) - solar cells. A novel combination of scanning electron microscopy and image processing is used to determine the degree of percolation of the AgNWs on large areas of the nano-composite AgNW/AZO electrodes. Our results show that the solar cell with percolated AgNW/AZO electrode show the highest short circuit current density (28 mA/cm(2)) and a series resistance in the same order of magnitude compared to reference solar cells with a thermally evaporated silver grid electrode. The electrode example we chose reveals that the developed AgNW/AZO electrode is a technologically relevant and cheap alternative to conventional solar cell screen printed grid electrodes, which contain similar to 95% more Ag per device area, with a high potential to be further systematically optimized by the presented image processing method.",
publisher = "Elsevier, Amsterdam",
journal = "Nano Energy",
title = "Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes",
pages = "206-196",
volume = "16",
doi = "10.1016/j.nanoen.2015.06.027"
}

Goebelt, M., Keding, R., Schmitt, S. W., Hoffmann, B., Jaeckle, S., Latzel, M., Radmilović, V., Radmilović, V. R., Spiecker, E.,& Christiansen, S.. (2015). Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes. in Nano Energy
Elsevier, Amsterdam., 16, 196-206.
https://doi.org/10.1016/j.nanoen.2015.06.027

Goebelt M, Keding R, Schmitt SW, Hoffmann B, Jaeckle S, Latzel M, Radmilović V, Radmilović VR, Spiecker E, Christiansen S. Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes. in Nano Energy. 2015;16:196-206.
doi:10.1016/j.nanoen.2015.06.027 .

Goebelt, Manuela, Keding, Ralf, Schmitt, Sebastian W., Hoffmann, Bjoern, Jaeckle, Sara, Latzel, Michael, Radmilović, Vuk, Radmilović, Velimir R., Spiecker, Erdmann, Christiansen, Silke, "Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes" in Nano Energy, 16 (2015):196-206,
https://doi.org/10.1016/j.nanoen.2015.06.027 . .

TY  - JOUR
AU  - Guo, Fei
AU  - Li, Ning
AU  - Fecher, Frank W.
AU  - Gasparini, Nicola
AU  - Quiroz, Cesar Omar Ramirez
AU  - Bronnbauer, Carina
AU  - Hou, Yi
AU  - Radmilović, Vuk
AU  - Radmilović, Velimir R.
AU  - Spiecker, Erdmann
AU  - Forberich, Karen
AU  - Brabec, Christoph J.
PY  - 2015
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3116
AB  - The multi-junction concept is the most relevant approach to overcome the Shockley-Queisser limit for single-junction photovoltaic cells. The record efficiencies of several types of solar technologies are held by series-connected tandem configurations. However, the stringent current-matching criterion presents primarily a material challenge and permanently requires developing and processing novel semiconductors with desired bandgaps and thicknesses. Here we report a generic concept to alleviate this limitation. By integrating series-and parallel-interconnections into a triple-junction configuration, we find significantly relaxed material selection and current-matching constraints. To illustrate the versatile applicability of the proposed triple-junction concept, organic and organic-inorganic hybrid triple-junction solar cells are constructed by printing methods. High fill factors up to 68% without resistive losses are achieved for both organic and hybrid triple-junction devices. Series/parallel triple-junction cells with organic, as well as perovskite-based subcells may become a key technology to further advance the efficiency roadmap of the existing photovoltaic technologies.
PB  - Nature Publishing Group, London
T2  - Nature Communications
T1  - A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells
VL  - 6
DO  - 10.1038/ncomms8730
ER  - 

@article{
author = "Guo, Fei and Li, Ning and Fecher, Frank W. and Gasparini, Nicola and Quiroz, Cesar Omar Ramirez and Bronnbauer, Carina and Hou, Yi and Radmilović, Vuk and Radmilović, Velimir R. and Spiecker, Erdmann and Forberich, Karen and Brabec, Christoph J.",
year = "2015",
abstract = "The multi-junction concept is the most relevant approach to overcome the Shockley-Queisser limit for single-junction photovoltaic cells. The record efficiencies of several types of solar technologies are held by series-connected tandem configurations. However, the stringent current-matching criterion presents primarily a material challenge and permanently requires developing and processing novel semiconductors with desired bandgaps and thicknesses. Here we report a generic concept to alleviate this limitation. By integrating series-and parallel-interconnections into a triple-junction configuration, we find significantly relaxed material selection and current-matching constraints. To illustrate the versatile applicability of the proposed triple-junction concept, organic and organic-inorganic hybrid triple-junction solar cells are constructed by printing methods. High fill factors up to 68% without resistive losses are achieved for both organic and hybrid triple-junction devices. Series/parallel triple-junction cells with organic, as well as perovskite-based subcells may become a key technology to further advance the efficiency roadmap of the existing photovoltaic technologies.",
publisher = "Nature Publishing Group, London",
journal = "Nature Communications",
title = "A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells",
volume = "6",
doi = "10.1038/ncomms8730"
}

Guo, F., Li, N., Fecher, F. W., Gasparini, N., Quiroz, C. O. R., Bronnbauer, C., Hou, Y., Radmilović, V., Radmilović, V. R., Spiecker, E., Forberich, K.,& Brabec, C. J.. (2015). A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells. in Nature Communications
Nature Publishing Group, London., 6.
https://doi.org/10.1038/ncomms8730

Guo F, Li N, Fecher FW, Gasparini N, Quiroz COR, Bronnbauer C, Hou Y, Radmilović V, Radmilović VR, Spiecker E, Forberich K, Brabec CJ. A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells. in Nature Communications. 2015;6.
doi:10.1038/ncomms8730 .

Guo, Fei, Li, Ning, Fecher, Frank W., Gasparini, Nicola, Quiroz, Cesar Omar Ramirez, Bronnbauer, Carina, Hou, Yi, Radmilović, Vuk, Radmilović, Velimir R., Spiecker, Erdmann, Forberich, Karen, Brabec, Christoph J., "A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells" in Nature Communications, 6 (2015),
https://doi.org/10.1038/ncomms8730 . .