The onset of copper-ion mobility and the electronic transition in the kesterite Cu2ZnGeSe4
| Autor: | Ronald I. Smith, Paz Vaqueiro, Panagiotis Mangelis, Anthony V. Powell |
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| Rok vydání: | 2021 |
| Předmět: |
Phase transition
Materials science Condensed matter physics Renewable Energy Sustainability and the Environment General Chemistry engineering.material Thermoelectric materials Degenerate semiconductor Condensed Matter::Materials Science Differential scanning calorimetry Phase (matter) Seebeck coefficient Thermoelectric effect engineering General Materials Science Kesterite |
| Zdroj: | Journal of Materials Chemistry A. 9:27493-27502 |
| ISSN: | 2050-7496 2050-7488 |
| DOI: | 10.1039/d1ta08642a |
| Popis: | Kesterite-structured phase have attracted considerable interest as earth-abundant photovoltaic and thermoelectric materials. For the kesterite, Cu2ZnGeSe4, we have established a direct link between anomalies in the temperature dependence of transport properties and an order-disorder transition. Powder neutron diffraction as a function of temperature, reveals an order-disorder transition at 473 K, involving disordering of copper and zinc cations over three crystallographic positions. Vacancies are simultaneously created on the copper-ion sub-lattice, indicative of the concomitant onset of copper-ion mobility. Differential scanning calorimetry data show a weak thermal signature in this temperature region, typical of a second-order phase transition, which is consistent with the absence of anomalies in the temperature dependence of the unit cell volume. The partial melting of the copper-ion sub-lattice induces a transition in the electrical-transport properties. The changes in electrical resistivity and Seebeck coefficient suggest this involves a transition from a conventional, activated semiconductor, to a degenerate semiconductor. The entry of an increasing fraction of the copper-ion sub-lattice into a liquid-like state is reflected in a reduction in thermal conductivity above 473 K. The order-disorder phase transition identified here has consequences for the performance of photovoltaic and thermoelectric devices based on kesterites. |
| Databáze: | OpenAIRE |
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