Parisi, Jürgen

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Parisi, Jürgen
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Parisi, Jürgen

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2018 - 20203

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    Item-typ:Veröffentlichung,
    Organoboron donor-π-acceptor chromophores for small-molecule organic solar cells
    (Springer, 2018-07-26)
    Nolasco, Jairo C
    ;
    Ryan, James W.
    ;
    Rodriguez, M.
    ;
    Castro-Carranza, Alejandra
    ;
    Maldonado, José-Luis
    We introduce the use of facilely synthesizable and low-bandgap boron chromophores as donors in planar heterojunction solar cells. We show that simple changes in the compositional properties of these molecules can improve the performance of the devices. A simultaneous grafting of NO2 acceptor and N(Et2) donor groups into the molecule core causes an increase in efficiency of almost 50%. Such enhanced efficiency is mainly due to a higher photocurrent. The origin of this phenomenon is investigated.
    Wissenschaftlicher Artikel
    Band:29
      42  94
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    Item-typ:Veröffentlichung,
    Effects of Particle Size on Strong Metal–Support Interactions Using Colloidal “Surfactant-Free” Pt Nanoparticles Supported on Fe3O4
    (American Chemical Society, 2020-03-18)
    Neumann, Sarah
    ;
    Doebler, Hans Hannes
    ;
    Keil, Simona
    ;
    Erdt, Alexandra J.
    ;
    Gutsche, Christian
    Colloidal “surfactant-free” Pt nanoparticles (NPs) within the size range 1–4 nm supported on Fe3O4 were synthesized and applied as model systems to systematically study the role of size effects for strong metal–support interactions (SMSIs) with CO oxidation as a model reaction. Kinetic studies, isotopic labeling experiments with 18O2, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were applied to explore the reaction mechanism and the surface of the catalyst before and after reductive pretreatments. It was found that pure iron oxide was catalytically active in CO oxidation, and experimental evidence for a Mars van Krevelen mechanism between CO and lattice O was found. The turnover frequencies (TOFs) for small Pt NPs (≤3 nm) supported on iron oxide and normalized to the number of Pt atoms located at the periphery of the Pt–support interface were similar under reaction conditions, indicating that the reaction mainly proceeds at the interface. However, with increasing particle size, the contribution of a Langmuir–Hinshelwood mechanism of chemisorbed CO and O2 in addition to the Mars van Krevelen mechanism increases. After reductive pretreatment, the activity of the catalyst decreased significantly, which could be related to partial encapsulation of the monometallic Pt NPs with FeOx. To study whether also on the nanoscale an interaction between Pt and iron oxide similar to the beneficial or detrimental SMSI effect observed for the Pt particles supported on iron oxide can also be achieved, bimetallic Fe–Pt NPs of a mean size of 3–4 nm were deposited on inert Al2O3. It could be shown that surface segregation of Fe and formation of FeOx after reduction and exposure to oxygen took place. As a result, the activity of bimetallic NPs decreased due to loss of active Pt surface, revealing an effect similar to the detrimental SMSI detected for Pt NPs on FeOx support after reductive pretreatment.
    Wissenschaftlicher Artikel
    Band:10
    Heft:7
      71  23
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    Understanding the open circuit voltage in organic solar cells on the basis of a donor-acceptor abrupt (p-n++) heterojunction
    (Elsevier Science, 2019-05-15)
    Nolasco, Jairo C
    ;
    Castro-Carranza, Alejandra
    ;
    Arredondo Leon, Yesenia
    ;
    Briones-Jurado, Claudia
    ;
    Gutowski, Jürgen
    By using electrical characterization and classical solid state semiconductor device theory, we demonstrate that the open circuit voltage (Voc) in organic solar cells based on non-intentional doped semiconductors is fundamentally limited by the built-in potential (Vbi) originated at a donor-acceptor abrupt (p-n++) heterojunction in case of selective contacts. Our analysis is validated using P3HT:PCBM devices fabricated in our research group. We also demonstrate that such a result can be generalized using data already reported in literature for fullerene-based solar cells. Finally, we show that the dependence of Voc on the device contacts can be understood in terms of the potential barriers formed by the Fermi level alignment of semiconductors at the heterojunction and at the Schottky junctions.
    Wissenschaftlicher Artikel
    Band:184
      50  27