Armin Wedel

Dr. Armin Wedel

Fraunhofer Institute for Applied Polymer Research, Geiselbergstrasse 69, 14476 Potsdam Germany

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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22 June 2012 in Journal of Information Display
Verified
Journal Article
Open access
CIChristian Ippen
Christian Ippen
TGTonino Greco
Tonino Greco
AWArmin Wedel
Armin Wedel
Indium phosphide (InP) quantum dots (QDs) are considered alternatives to Cd-containing QDs for application in light-emitting devices. The multishell coating with ZnSe/ZnS was shown to improve the photoluminescence quantum yield (QY) of InP QDs more strongly than the conventional ZnS shell coating. Structural proof for this system was provided by X-ray diffraction and transmission electron microscopy. QY values in the range of 50–70% along with peak widths of 45–50 nm can be routinely achieved, making the optical performance of InP/ZnSe/ZnS QDs comparable to that of Cd-based QDs. The fabrication of a working electroluminescent light-emitting device employing the reported material demonstrated the feasibility of the desired application.

7 September 2022 in Small
Verified
Journal Article
Open access
JKJiyong Kim
Jiyong Kim
Yohan KimYohan Kim
Yohan Kim
KPKyoungwon Park
Kyoungwon Park
CBChristine Boeffel
Christine Boeffel
HCHyung‐Seok Choi
Hyung‐Seok Choi
AWArmin Wedel
Armin Wedel
The lack of anionic carboxylate ligands on the surface of InP/ZnSe/ZnS quantum dots (QDs), where zinc carboxylate ligands can be converted to carboxylic acid or carboxylate ligands via proton transfer by 1‐octanethiol, is demonstrated. The as‐synthesized QDs initially have an under‐coordinated vacancy surface, which is passivated by solvent ligands such as ethanol and acetone. Upon exposure of 1‐octanethiol to the QD surface, 1‐octanethiol effectively induces the surface binding of anionic carboxylate ligands (derived from zinc carboxylate ligands) by proton transfer, which consequently exchanges ethanol and acetone ligands that bind on the incomplete QD surface. These systematic chemical analyses, such as thermogravimetric analysis‐mass spectrometry and proton nuclear magnetic resonance spectroscopy, directly show the interplay of surface ligands, and it associates with QD light‐emitting diodes (QD‐LEDs). It is believed that this better understanding can lead to industrially feasible QD‐LEDs.

11 January 2024 in Nature Photonics
Verified
Journal Article
Open access
PDF file
KPKyoungwon Park
Kyoungwon Park
JYJeongmin Yi
Jeongmin Yi
SYSuk-Young Yoon
Suk-Young Yoon
SPSeong Min Park
Seong Min Park
JKJiyong Kim
Jiyong Kim
CHChul Jong Han
Chul Jong Han
Luminescent solar concentrators (LSCs) have the potential to serve as energy-harvesting windows in buildings. Although recent advances in nanotechnology have led to the emergence of novel fluorophores such as quantum dots, perovskites and others, the commercialization of such functional glass remains immature due to an insufficient power conversion efficiency. In other words, improvements in fluorophores alone cannot fully maximize the potential of LSCs. Here we introduce a new laminated type of LSC structure where a patterned low-refractive-index medium acts as an optical ‘guard rail’, providing a practically non-decaying path for guiding photons. We also propose the design rules regarding the dimensions of LSCs and the spectral characteristics of fluorophores. Once these rules were applied, we achieved record-high LSC performance. The measured external quantum efficiencies at 450 nm are 45% for a 100 cm2 area and 32% for the LSC with an edge aspect ratio of 71. The device efficiency is 7.6%, the highest value ever reported, to the best of our knowledge. These findings may have industrial implications and could accelerate the commercialization of LSCs.

1 February 2021 in ChemistryOpen
Verified
Journal Article
Open access
PDF file
CBChristian Balischewski
Christian Balischewski
HCHyung‐Seok Choi
Hyung‐Seok Choi
KBKarsten Behrens
Karsten Behrens
ABAlkit Beqiraj
Alkit Beqiraj
TKThomas Körzdörfer
Thomas Körzdörfer
Andreas TaubertAndreas Taubert
Andreas Taubert
Metal sulfides are among the most promising materials for a wide variety of technologically relevant applications ranging from energy to environment and beyond. Incidentally, ionic liquids (ILs) have been among the top research subjects for the same applications and also for inorganic materials synthesis. As a result, the exploitation of the peculiar properties of ILs for metal sulfide synthesis could provide attractive new avenues for the generation of new, highly specific metal sulfides for numerous applications. This article therefore describes current developments in metal sulfide nanoparticle synthesis as exemplified by a number of highlight examples. Moreover, the article demonstrates how ILs have been used in metal sulfide synthesis and discusses the benefits of using ILs over more traditional approaches. Finally, the article demonstrates some technological challenges and how ILs could be used to further advance the production and specific property engineering of metal sulfide nanomaterials, again based on a number of selected examples.

7 February 2018 in The Journal of Chemical Physics
Verified
Journal Article
Closed access
PDF file
YKYohan Kim
Yohan Kim
BHBenjamin Heyne
Benjamin Heyne
AAAhed Abouserie
Ahed Abouserie
CPChristopher Pries
Christopher Pries
CIChristian Ippen
Christian Ippen
AWArmin Wedel
Armin Wedel
Hexagonal p-type semiconductor CuS nanoplates were synthesized via a hot injection method from bis(trimethylsilyl)sulfide and the ionic liquid precursor bis(N-dodecylpyridinium) tetrachloridocuprate(ii). The particles have a broad size distribution with diameters between 30 and 680 nm and well-developed crystal habits. The nanoplates were successfully incorporated into organic photovoltaic (OPV) cells as hole conduction materials. The power conversion efficiency of OPV cells fabricated with the nanoplates is 16% higher than that of a control device fabricated without the nanoplates.

1 July 2015 in Journal of the Society for Information Display
Verified
Journal Article
Closed access
PDF file
CIChristian Ippen
Christian Ippen
TGTonino Greco
Tonino Greco
YKYohan Kim
Yohan Kim
CPChristopher Pries
Christopher Pries
Jiwan KimJiwan Kim
Jiwan Kim
AWArmin Wedel
Armin Wedel