Structural phase transitions on hybrid organic-inorganic halide perovskites based on bromide

• Ano de defesa: 2019
• Autor(a) principal: Rodriguez Hernandez, Juan Simón
• Orientador(a): Paschoal, Carlos William de Araújo
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Palavras-chave em Português: Perovskita; Transformações de fase (Física Estatística); Raios-X - Difração; Espectroscopia Raman
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/45331

Halide inorganic-organic perovskite (HIOP) are promising new functional materials for solar cell applications as other optoelectronic performance such as light emitting diodes, low-threshold lasers, and photodetectors. The halide modification in the perovskite crystal structure represented in the material different applications and properties, important research groups and industries today are seeking organics replacement in the crystal composition. One of the natural changes is the dimethylammonium [(CH3)2NH2]+ (DMA) organic cation because is highly responsible for ordering in the crystal structure, and in most cases responsible for the ferroelectric order. In this context, we discuss with a DFT calculation the vibrational assignation in the DMA molecule for a modest attribution, also we have prepared with the bromide halide and DMA two perovskites compositions by using simple lab conditions at room temperature. These compounds exhibit a phase crystal transition, where the order-disorder mechanics act. One of synthesized material is the hexagonal three-dimensional DMAPbBr3 perovskite; we found with our X-ray diffraction, differential scanning calorimetric and Raman spectroscopy measurements at 250 K a phase crystal transition for hexagonal to an orthorhombic system. On the other hand, we described with Raman spectroscopy in low-temperature the isostructural phase transition of two-dimensional DMA7Pb4Br15, in both compounds, the stretching H-bond in the CH3 groups at high frequencies is the ones who are responsible for the ordering in DMA organic cation. These materials not only open large possibilities and applications of differences electrical and optical properties, but they also have advantages as an easy synthesized method and cheap materials and low-temperature formation.