University of Bucharest, Faculty of Physics
   Dr. George Alexandru NEMNES
   ICUB
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Perovskite solar cells




Published papers:

  • G. A. Nemnes, Cristina Besleaga, Andrei Gabriel Tomulescu, Alexandra Palici, Lucian Pintilie, Andrei Manolescu and Ioana Pintilie,
    "How measurement protocols influence the dynamic J-V characteristics of perovskite solar cells: theory and experiment",
    Solar Energy 173, 976 (2018)
  • G. A. Nemnes, Cristina Besleaga, Viorica Stancu, Daniela Emilia Dogaru, Lucia Nicoleta Leonat,
    L. Pintilie, K. Torfason, M. Ilkov, A. Manolescu, Ioana Pintilie,
    "Normal and inverted hysteresis in perovskite solar cells",
    J. Phys. Chem. C 121, 11207 (2017)
    (arXiv:1704.03300)
  • G. A. Nemnes, Cristina Besleaga, A. G. Tomulescu, Ioana Pintilie, L. Pintilie, K. Torfason, A. Manolescu,
    "Dynamic electrical behavior of halide perovskite based solar cells",
    Sol. Energy Mater. Sol. Cells 159, 197 (2017)
  • N. Plugaru, G. A. Nemnes, L. Filip, Ioana Pintilie, L. Pintilie, K. T. Butler and Andrei Manolescu,
    "Atomistic Simulations of Methylammonium Lead Halide Layers on PbTiO3 (001) Surfaces",
    J. Phys. Chem. C 121, 9096 (2017)
  • Cristina Besleaga, Laura Elena Abramiuc, Viorica Stancu, A. G. Tomulescu, M. Sima, Liliana Trinca, N. Plugaru,
    L. Pintilie, G. A. Nemnes, Mihaiela Iliescu, H. G. Svavarsson, A. Manolescu and Ioana Pintilie,
    "Iodine Migration and Degradation of Perovskite Solar Cells Enhanced by Metallic Electrodes",
    J. Phys. Chem. Lett. 7, 5168 (2016)
  • Adela Nicolaev, T. L. Mitran, Sorina Iftimie, G. A. Nemnes,
    "Optimization of halide perovskite solar cells based on nanocolumnar ZnO",
    Sol. Energy Mater. Sol. Cells 158, 202 (2016)
  • G. A. Nemnes, C. Goehry, T. L. Mitran, Adela Nicolaev, L. Ion, S. Antohe, N. Plugaru, A. Manolescu,
    "Band alignment and charge transfer in rutile-TiO2/CH3NH3PbI3-xClx interfaces",
    Phys. Chem. Chem. Phys. 17, 30417 (2015)
  • C. Goehry, G. A. Nemnes and Andrei Manolescu,
    "Collective Behavior of Molecular Dipoles in CH3NH3PbI3",
    J. Phys. Chem. C 119, 19674 (2015)

Finalized research project:


Ongoing research:

  • DFT simulations of hybrid perovskite layers on ferroelectric PbTiO3(001) surfaces
  • Band alignment of Cu2O/perovskite interface
  • Normal and inverted hysteresis

Main results:

  1. Modeling hysteresis in perovskite solar cells -- Dynamic Electrical Model (DEM)
    • Pre-poling bias is causing the current overshoot in reverse J-V characteristics
    • The hysteresis is minimal at low and high bias scan rates, which is explained by the dynamic electrical model (DEM)
    hysteresis in perovskite solar cell hysteresis in perovskite solar cell
    G. A. Nemnes, Cristina Besleaga, A. G. Tomulescu, Ioana Pintilie, L. Pintilie, K. Torfason, A. Manolescu,
    "Dynamic electrical behavior of halide perovskite based solar cells",
    Sol. Energ. Mater. & Sol. Cells 159, 197 (2017)
    arXiv:1606.00335

    ***Citations:
    • S. Ravishankar, O. Almora, C. Echeverria-Arrondo, E. Ghahremanirad, C. Aranda, A. Guerrero,
      F. Fabregat-Santiago, A. Zaban, G. Garcia-Belmonte, and J. Bisquert,
      "Surface Polarization Model for the Dynamic Hysteresis of Perovskite Solar Cells",
      J. Phys. Chem. Lett. 8, 915 (2017)

  2. Degradation is enhanced by the presence of metalic electrodes
    • Aged structures without metallic electrodes behave as fresh ones when adding the back contact
    • Iodine migration is confirmed by XPS experiments
    ion migration perovskite solar cell ion migration perovskite solar cell
    Cristina Besleaga, Laura Elena Abramiuc, Viorica Stancu, A. G. Tomulescu, M. Sima, Liliana Trinca, N. Plugaru,
    L. Pintilie, G. A. Nemnes, Mihaiela Iliescu, H. G. Svavarsson, A. Manolescu and Ioana Pintilie,
    "Iodine Migration and Degradation of Perovskite Solar Cells Enhanced by Metallic Electrodes",
    J. Phys. Chem. Lett. 7, 5168 (2016)


  3. Nanocolumnar ZnO perovskite solar cells
    • AZO interfacial layer produces a spike-less band diagram
    • Optimized structures based on the Perovskite/AZO/ZnO layer sequence have enhanced PCEs
    ZnO perovskite solar cells ZnO perovskite solar cells
    Adela Nicolaev, T. L. Mitran, Sorina Iftimie, G. A. Nemnes,
    "Optimization of halide perovskite solar cells based on nanocolumnar ZnO",
    Sol. Energy Mater. Sol. Cells 158, 202 (2016)


  4. Chlorine effect on the band alignment in rutile-TiO2/CH3NH3PbI3-xClx interfaces
    • A certain concentration of chlorine is needed for optimal band offsets
    • Large chlorine concentrations may significantly decrease the valence band offset
    band alignment perovskite solar cell band alignment perovskite solar cell
    G. A. Nemnes, C. Goehry, T. L. Mitran, Adela Nicolaev, L. Ion, S. Antohe, N. Plugaru, A. Manolescu,
    "Band alignment and charge transfer in rutile-TiO2/CH3NH3PbI3-xClx interfaces",
    Phys. Chem. Chem. Phys. 17, 30417 (2015)


  5. Microscopic ferroelectricity in hybrid perovskite
    • Ab initio evidence of microscopic ferroelectricity, which elegantly explains the lack of macroscopic ferroelectricity
    • Rotational relaxation times of dipoles is of the order of a few tens of ps
    ferroelectricity perovskite solar cell ferroelectricity perovskite solar cell
    C. Goehry, G. A. Nemnes and Andrei Manolescu,
    "Collective Behavior of Molecular Dipoles in CH3NH3PbI3",
    J. Phys. Chem. C 119, 19674 (2015)
  

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