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    Relationship between the VOC Tuning Effect and the Interface Activation Energy Due to the Third Component Concentration in Ternary Organic Solar Cells
    The open-circuit voltage (VOC) tuning effect due to the variation of the low concentration of the third component in ternary organic solar cells has been mainly attributed to interfacial phenomena. Up to date, the models reported in the literature to analyze such interfacial phenomena are based on optical characterization. In this work is proposed a different approach to study such a VOC tuning effect by using dark-current characteristics at different temperatures. Specifically, for PTB7-Th:PC71BM:ICBA-based solar cells, it is found that an increment of the third component concentration, that is, the fullerene ICBA, causes an increase in the activation energies (Ea) in an Arrhenius-type curve. This, in turn, decreases the reverse saturation current (J0) of the devices, thereby incrementing their VOC.
    Wissenschaftlicher Artikel
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      40  51
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    Numerical simulation of a bilayer organic solar cell based on boron chromophore compounds as acceptors
    Organic solar cells fabricated with non-fullerene acceptors have proven to be a solution to reduce manufacturing costs. Besides the material selection, another way to reduce such costs is by optimizing the properties of both the materials and the interfaces which in turn would contribute to enhance the solar cells efficiency. This can be done with numerical simulations. Among non-fullerene materials, boron chromophores are relatively stable and chemically versatile compounds which have been usually used as donors in solar cells. In this work, planar solar cells based on PTB7 and boron compounds are proposed and simulated but by using the latter as acceptors. Specifically, we show the functionality of our proposed devices by analyzing the variation of both the Lowest Unoccupied Molecular Orbital (LUMO) and the influence of the non-intentional doping of the boron compounds with regard to the photovoltaic parameters of the solar cells. The properties of the materials such as the dielectric constant, energy levels, and non-intentional doping are taken from literature. We show that there are optimal values for LUMO and doping concentration to maximize the device efficiency. The causes of this behavior are analyzed using band diagram simulations.
    Konferenzbeitrag
      53  40
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    Item-typ:Veröffentlichung,
    Organoboron donor-π-acceptor chromophores for small-molecule organic solar cells
    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
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      42  93
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    Item-typ:Veröffentlichung,
    Numerical study of efficient ternary planar hybrid solar cells using simple boron molecules as organic compounds
    Ternary solar cells have proven to be a solution to absorb more photons at different wavelengths and reduce the recombination of charge carriers. Here, we propose a new hybrid organic-inorganic ternary planar solar-cell structure using a novel boron compound. The role of this material on the performance of the device with a polymer/borinate/ZnO configuration is studied. As the donor polymer, we evaluate P3HT, PTB7, and PCPDTBT; and three boron compounds with different properties, especially concerning the bandgap and trap energy depth. To validate the experimental electrical characteristics of the borinates, first, we simulate a bilayer structure with C60, subsequently, we simulate and analyze the whole device architecture. The ternary solar cell with PTB7 and a borinate with a bandgap of 1.66 eV and a medium trap energy depth of 0.95 eV above the HOMO level exhibit the highest efficiency, i. e. 11.7%. Furthermore, we present a layer thickness optimization of the materials to reach even higher efficiencies, up to 15.15%. Finally, the effect of the magnitude of the density of trap states in the borinate on the device performance is analyzed.
    Wissenschaftlicher Artikel
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      49  67