@article{WangFritschBerendtsetal.2021,
  author    = {Wang, Zhenyu and Fritsch, Daniel and Berendts, Stefan and Lerch, Martin and Breternitz, Joachim and Schorr, Susan},
  title     = {Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis},
  series = {Chemical science / RSC, Royal Society of Chemistry},
  volume    = {12},
  journal   = {Chemical science / RSC, Royal Society of Chemistry},
  number    = {24},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2041-6539},
  doi       = {10.1039/d1sc00328c},
  pages     = {8493 -- 8500},
  year      = {2021},
  abstract  = {Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials.},
  language  = {en}
}
@inproceedings{BreternitzSchorr2021,
  author    = {Breternitz, Joachim and Schorr, Susan},
  title     = {Halide perovskites},
  series = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  volume    = {77},
  booktitle = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  number    = {Suppl.},
  publisher = {Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {2053-2733},
  doi       = {10.1107/S0108767321089479},
  pages     = {C750 -- C750},
  year      = {2021},
  language  = {en}
}
@misc{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51822},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518227},
  pages     = {7},
  year      = {2019},
  abstract  = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.},
  language  = {en}
}
@article{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3},
  series = {Angewandte Chemie - international edition},
  volume    = {59},
  journal   = {Angewandte Chemie - international edition},
  number    = {1},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {New Jersey},
  pages     = {5},
  year      = {2019},
  abstract  = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.},
  language  = {en}
}
@phdthesis{Breternitz2023,
  author    = {Breternitz, Joachim},
  title     = {Structural systematic investigations of photovoltaic absorber materials},
  school      = {Universit{\"a}t Potsdam},
  pages     = {189},
  year      = {2023},
  abstract  = {The direct conversion of light from the sun into usable forms of energy marks one of the central cornerstones of the change of our living from the use of fossil, non-renewable energy resources towards a more sustainable economy. Besides the necessary societal changes necessary, it is the understanding of the solids employed that is of particular importance for the success of this target. In this work, the principles and approaches of systematic-crystallographic characterisation and systematisation of solids is used and employed to allow a directed tuning of the materials properties. The thorough understanding of the solid-state forms hereby the basis, on which more applied approaches are founded. Two material systems, which are considered as promising solar absorber materials, are at the core of this work: halide perovskites and II-IV-N2 nitride materials. While the first is renowned for its high efficiencies and rapid development in the last years, the latter is putting an emphasis on true sustainability in that toxic and scarce elements are avoided.},
  language  = {en}
}
@article{BreternitzSchorr2021,
  author    = {Breternitz, Joachim and Schorr, Susan},
  title     = {Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc2(1)},
  series = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  volume    = {77},
  journal   = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  number    = {3},
  publisher = {Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {2053-2733},
  doi       = {10.1107/S2053273320015971},
  pages     = {208 -- 216},
  year      = {2021},
  abstract  = {Binary III-V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on this matter. The non-existence of compounds crystallizing in Pmc2(1), formally the highest subgroup of the wurtzite type fulfilling Pauling's rules for 1:1:2 stoichiometries, has been puzzling scientists for a while; a rationalization is given, from a crystallographic basis, of why this space group is unlikely to be adopted.},
  language  = {en}
}
@misc{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Zur Rolle der Iodid-Methylammonium-Interaktion in der Ferroelektrizit{\"a}t in CH3NH3PbI3},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.1002/ange.201910599},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525674},
  pages     = {7},
  year      = {2019},
  abstract  = {Ihre außergew{\"o}hnlich hohen Konversionseffizienzen von {\"u}ber 20 \% und die einfache Zellherstellung machen Hybridperowskite zu heißen Kandidaten f{\"u}r alternative Solarzellenmaterialien. CH3NH3PbI3 als Archetyp dieser Materialklasse besitzt außergew{\"o}hnliche Eigenschaften wie eine sehr effiziente Umwandlung von Solarenergie, wobei besonders Ferroelektrizit{\"a}t als m{\"o}gliche Erkl{\"a}rung in den Fokus ger{\"u}ckt ist. Diese erfordert allerdings eine nicht-zentrosymmetrische Kristallstruktur als notwendige Voraussetzung. Wir stellen hier eine Erkl{\"a}rung des Symmetriebruchs in diesem Material auf kristallographischem, d. h. fernordnungs-basiertem, Wege vor. W{\"a}hrend das Molek{\"u}lkation CH3NH3+ intrinsisch polar ist, ist es extrem fehlgeordnet und kann deshalb nicht die einzige Erkl{\"a}rung darstellen. Es verzerrt allerdings das umgebende Kristallgitter und ruft dadurch eine Verschiebung der Iod-Atome von den zentrosymmetrischen Positionen hervor.},
  language  = {de}
}
@article{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Zur Rolle der Iodid-Methylammonium-Interaktion in der Ferroelektrizit{\"a}t in CH3NH3PbI3},
  series = {Angewandte Chemie},
  volume    = {132},
  journal   = {Angewandte Chemie},
  number    = {1},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {New Jersey},
  pages     = {5},
  year      = {2019},
  abstract  = {Ihre außergew{\"o}hnlich hohen Konversionseffizienzen von {\"u}ber 20 \% und die einfache Zellherstellung machen Hybridperowskite zu heißen Kandidaten f{\"u}r alternative Solarzellenmaterialien. CH3NH3PbI3 als Archetyp dieser Materialklasse besitzt außergew{\"o}hnliche Eigenschaften wie eine sehr effiziente Umwandlung von Solarenergie, wobei besonders Ferroelektrizit{\"a}t als m{\"o}gliche Erkl{\"a}rung in den Fokus ger{\"u}ckt ist. Diese erfordert allerdings eine nicht-zentrosymmetrische Kristallstruktur als notwendige Voraussetzung. Wir stellen hier eine Erkl{\"a}rung des Symmetriebruchs in diesem Material auf kristallographischem, d. h. fernordnungs-basiertem, Wege vor. W{\"a}hrend das Molek{\"u}lkation CH3NH3+ intrinsisch polar ist, ist es extrem fehlgeordnet und kann deshalb nicht die einzige Erkl{\"a}rung darstellen. Es verzerrt allerdings das umgebende Kristallgitter und ruft dadurch eine Verschiebung der Iod-Atome von den zentrosymmetrischen Positionen hervor.},
  language  = {de}
}